KENDRIYA VIDYALAYA SANGATHAN
GUWAHATI REGION
STUDY MATERIAL(HOTS)
CLASS X
SCIENCE
2008-09
Co-ordinator:
E.C.Moore
Principal,K.V.Borjhar
Prepared by:
Mrs.Sibani Chakraborty
Mrs.Samita Mech
Mrs Meera Baruah
TGT (Sc)
TGT (Sc)
TGT (Sc)
K.V.Borjhar
K.V.Borjhar
K.V.Borjhar
Chapter -1
Chemical Reactions and Equations
Q.1. What is the general name of substances which are added to fat & oil
containing
food to prevent rancidity.
(1 Mark)
Ans. Antioxidants
Q.2. Write balanced chemical equation for the reaction of barium chloride
with
Aluminium sulphate.
(1 Mark)
Ans. 3 BaCl2 + Al2 (SO4)3
3 BaSO4 +2AlCl3.
Q.3. Identify the substance that is oxidised and the substance that is reduced in
the
following reaction. 4 Na+O2
Ans. Substance Oxidised
Substance reduced
2 Na2O
(1 Mark)
Na
O2
Q.4. Why does the colour of copper sulphate solution fade when iron nail is
dipped in
it.
Ans. The solution changes into iron sulphate Fe+CuSO4
(2 Mark)
FeSO4
+
Cu
Q.5. What happens when quick lime is added to water? Write the chemical
equation.
Which type of reaction is it endothermic or exothermic?
(2 Mark)
Ans. Calcium oxide reacts vigorously with water to produce slaked lime
(Calciumm hydroxide)
CaO+H2O
Ca (OH)2 +Heat energy. It is an exothermic reaction.
Q.6. Silver chloride turns grey when kept in sunlight. Write chemical equation
for it.
What type of reaction is it?
(2 Mark)
Ans. 2 Ag Cl Sunlight 2 Ag (S) + Cl2 (g). It is a decomposition reaction
where light energy is absorbed. So it is an endothermic reaction.
Q.7. What happens when potassium iodide solution is added to lead nitrate
solution? Give equation of the reaction involved. What type of reaction is
represented by this example?
(3marks)
Ans. When potassium iodide solution is added to lead nitrate solution, then a
yellow
precipitate of lead iodide is formed alongwith potassium nitrate solution
Pb(NO3)2 (aq) + 2KI (aq)
PbI2 (S) + 2 KNO3 (aq)
This is an example of a double displacement reaction. It is also a
precipitation
Reaction.
Q.8. When a green iron salt is heated strongly, its colour finally changes to
black and the odour of burning sulphur is given out.
a)
Name the iron salt.
b)
Name the type of reaction that take place during the heating of iron
salt.
c)
Write a chemical equation for the reaction involved.
(3 Marks)
Ans:- a) Ferrous Sulphate
b) Thermal decomposition
c) 2 FeSO4 (S) Heat
(Ferrous sulphate)
Green Colored
Fe2O3(s) + SO2 (g) + SO3 (g)
(ferric oxide)
Reddish brown.
Q. 9. Which type are the following reactions?
a) NH4Cl
b) Fe + CuSO4
NH3 + HCl.
Fe SO4 + Cu
c) Ag NO3 + NaCl
AgCl + NaNO3
d) PbO2 + SO2
PbSO4
e) CaCO3
CaO +CO2
(5 Marks)
Ans. a) Thermal decomposition reaction
b) Displacement reaction
c) Double displacement reaction
d) Combination reaction.
e) Thermal decomposition reaction
Q.10. Write balanced chemical equations for the following reactions:-
(5 Marks)
a) Dilute Sulphuric acid is poured on zinc granules
b) Iron reacts with steam
c) Carbon dixide reacts with water in the process of photosynthesis
d) Limestone is heated strongly.
e) Silver chloride is kept in sunlight in a china dish.
a) Zn + H2SO4
b) 3 Fe + 4H2O
ZnSO4 + H2.
Fe3O4 + 4 H2
c) 6CO2 + 6H2O Sunlight C6H12O6 +6O2
d) CaCo3 Heat Chlorophyll CaO +Co2
e) 2 Ag Cl
2 Ag + Cl2
Chapter 2
Acids, Bases & Salts
1. How is the concentration of hydronium ion (H3O+) affected when a solution
of an
acid is diluted?
(1 Mark)
Ans. The concentration of hydronium ions, decreases when a solution of an
acid is
Diluted.
2. Fresh milk has a PH of 6. How do you think the PH will change as it turns
into curd? (1 Mark)
Ans. Its PH will decrease due to the production of lactic acid which is acidic in
nature.
3. What is the PH of acid rains?
( 1 Mark )
Ans. Less than 5.6
4. Tooth enamel is one of the hardest substances in our body. How does it
undergo
damage due to eating chocolates & sweets. What should we do to prevent it
?. ( 2 marks )
Ans. The bacteria present in mouth produce acids by the degradation of sugar
& food
particles present in the mouth after eating. The acid so produced
corrodes tooth
Enamel (Ca3(PO4)2). In order to prevent tooth decay we should clean the
mouth
after eating food & we should use alkaline tooth paste.
5. Explain why for diluting an acid concentrated acid is added to water & not
water to concentrated acid ?
Ans. This is because the process of dissolution of an acid in water is highly
exothermic
process. For dilution the acid must be added slowly to water with
constant stirring.
If water is added to acid, the heat generated may cause the mixture to
splash
out and cause burns. The glass container
may also break due to
excessive local heating.
6. A house wife found that the cake prepared by her is hard and small in size.
Which
ingredients has she forgotten to add that would have made the cake fluffy?
Give
reason.
Ans. She has forgotten to add baking powder. When baking powder is added
[Sodium bicarbonate and tartaric acid mixture] during the preparation of cake
and heated then
sodium bicarbonate reacts with tartaric acid to form CO 2 gas. This CO2
evolved
makes the cake to rise and become light and fluffy. Since the cake
prepared by the
house wife is small and hard, it means that she had forgotten to add
baking
powder.
Q.7. You have been provided with three test tubes. One of them contains
distilled water
and the other two contain an acidic solution and a basic solution,
respectively. If you are given only red litmus paper, have will you identify the
contents of each test
tube?
Ans. Dip red litmus paper in solution repeatedly in each tube.
(a)
The tube in which the red litmus paper turns purple contains
distilled water.
(b)
The tube in which red litmus paper turns blue contains basic
solution.
(c)
The tube in which red litmus paper remains red contains
acidic solution.
Q.8. Do basic solutions also have H+ (aq) ions? If yes, then why are these
basic? What is an alkali ?
(3 Marks)
Ans:
Basic solutions also contain H+ (aq) ions. But in basic solutions:
[H+] < 10-7 M
(aq)
And (OH-) > 10-7 M
Since (OH-aq) is more than [H+aq]hence these are basic solutions.
Bases that are soluble in water are called alkalis. For example NaOH, KOH,
Ca(OH)2
Q. 9. What is neutralization reaction? Write 3 applications of neutralization
reaction.
Ans. Neutralization it is an interaction of an acid with a base to form salt and
water.
e.g. HCI + NaOH
Acid
Base
NaCl + H2 O
Salt
Water
Q. 10. Application :(i) Antacids neutralize the excess acids in our stomach and
relieve us
from pain Ex-magnesium hydroxide (milk of magnesia).
(ii) If the pH of the sail is less than 7 i.e. it is acidic, the farmer will treat
the soil
with quick time, slaked time, chalk etc to neutralize the acidity.
(iii) Bee sting contains methanoic acid which causes pain and irritation.
Use of
mild base. Ex baking soda neutralizes it.
Q 10. a) How do metal carbonates and metal hydrogen carbonates react with
acids?
Explain with the help of an activity.
(b) What happens when sulphuric acid in rain reacts with calcium carbonate in
buildings
Made from limestone? (5marks)
Ans. (a) All metal carbonates and hydrogen carbonates react with acids to form
a
corresponding salt, carbon dioxide & water.
Metal Carbonate + Acid -> Salt + Carbon dioxide + water
Metal hydrogencarbonate + Acid -> Salt + Carbon dioxide + Water.
For ex, Sodium carbonate reacts with dilute hydrochloric acid as
follows:Na2CO3 (S) + 2 HCI (aq) -> 2 NaCI (aq + H20 (l) + CO2 (g)
Sodium hydrogen carbonate reacts with dilute hydrochloric acid as
follows:-
NaHCO3 (S) + HCI (aq) -> NaCI (aq) + H2O(l) + C02 (g)
Activity :- Text book page number 20 Activity 2.5
Observation:- CO2 is produced with an effervescence. When this gas is
allowed to
pass through lime water it becomes cloudy. It is a test for
CO2.
b) When sulphuric acid in rain reacts with calcium carbonate in buildings
made
from limestone calcium sulphate and Carbon dioxide is produced.
CaCO3 + H2SO4 -> CaSO4 + CO2 + H2O.
Chapter -3
Metals & Non-Metals
Q.1. What would happen to a copper vessel if it is left for a few days in humid
atmosphere without being cleaned ? (1)
Ans:- The surface will get corroded with the formation of a green layer of
copper
carbonate.
Q.2. Why is ZnO Called an amphoteric oxide? Show with the help an equation.
Ans. ZnO is called an amphoteric oxide because it shows both acidic as well as
basic
behaviour, i.e., it reacts with both acids (eg. HCl) as well as bases(Eg.
NaOH) to form salt & water.
ZnO + 2HCl -> ZnCl2 + H2O
ZnO + 2 NaOH -> Na2 ZnO2 + H2O
Q.3. Write the chemical equation for the reaction of hot aluminium with steam.
Ans. 2 Al + 3 H2O -> Al2O3+ 3H2
Q4. An element reacts with oxygen to form an oxide which dissolves in dilute
HCl. The
Oxide also turns a solution of red litmus blue. Is the element a metal or a
non-metal?
Explain with help of a suitable example.
Ans. The element is a metal. Taking the example of Na Metal, its oxide will be
Na2O . It
dissolves dilute HCI as follows:
Na2O + 2 HCI -> 2NaCl + H2O
Na2O as well as all other metal oxides are basic. For example, Na 2O is basic as
it dissolves in water to form NaOH which is a base. Basic oxides turn red litmus
blue.
Q.5. Give reasons for the following:
(i) Carbon is not used for making aluminium from aluminium oxide.
(ii) Al easily combine with oxygen but still can be used for making kitchen
utensils. (2)
Ans. (i) Carbon is not used for making aluminium from aluminium oxide
because
aluminium has greater affinity to oxygen than for carbon. Hence carbon
cannot
reduce aluminium oxide to aluminium.
(ii)Aluminium easily combines with 02 to form a layer of aluminium oxide. This
layer, however, acts as a protective layer and doesn’t allow the metal
underneath to react further.
Q.6. What is activity series of metals? Arrange Al, Zn, and Mg. in an increasing
order
of
reactivity.
(2)
Ans. The arrangement of metals in order of their decreasing reactivity with
respect to other is called activity series of metals. The increasing order of the
given metals is: Hg < Zn < Al.
Q.7. Give reason for the following.
i) Metals are regarded as electropositive elements.
ii) When a piece of copper is added to a solution of zinc sulphate, no change
taken place, but the blue colour of copper sulphate fades away when a piece of
zinc is placed in the reaction.
(iii) Reaction of HNO3 with metals generally doesn’t evolve H2 gas. (3)
Ans. (i) Metals have a tendency to lose one or more electrons to form positive
ions, thus are called electropositive elements.
(ii) a) When copper metal is added to ZnSO4 solution no change takes place
because Zn is more reactive than Cu.
b) When Zn is added to CuSO4 solution, the colour fades because Zn is more
reactive than Cu. It forms ZnSO4.
Zn + CuSO4 -> Zn SO4 + Cu
(iii) Reaction of metals with HNO3 doesn’t evolve H2 gas. It is because HNO3 is
a strong oxidizing agent. It oxidizes H2 produced to water and is itself reduced
to any of its oxides such as N20. NO. or NO2.
Q8. Write chemical equations for the reactions taking place when
i)
Zinc carbonate is calcined
ii)
Cinnabar (HgS) is heated in the air.
iii)
Manganese dioxide is heated with aluminium powder.
(3)
Ans. i) Zn CO3 (S) Calcination ZnO (S) + CO2 (g)
ii) 2HgS (S) + 302 (g) Heat 2HgO (S) + 2SO2 (g)
2HgO-> 2Hg (l) + O2 (g)
iv) 3MnO2 + 4 Al. Heat 2Al2O3 + 3 Mn.
Q. 9. a) What is ionic bond?
b) How ionic bond is formed?
c) Write the formation of magnesium chloride.
(5)
Ans. (a) The Chemical bond found by the transfer of electrons from one atom to
another
is known as an ionic bond.
(b) An ionic bond is formed when one of the atoms can donate electrons to
achieve the inert gas electronic configuration and other atoms need
electrons to achieve the inert gas electronic configuration. When a metal
(Usually 1, 2 or 3 electrons in outermost shell) reacts with a non-metal
(usually 5, 6 or 7 electron in outermost shell), transfer of electrons takes
place from metal atoms to the non-metal atoms and an ionic bond is
formed.
(c) Formation of magnesium chloride (MgCl2). The atomic number of
magnesium is 12. it has two electrons in its valence shell as shown
below:
12 Mg – 2, 8, 2
Magnesium, therefore, has a tendency to lose the 2 valence electrons and
in the
process attains the electronic configuration of neon
Mg-> Mg 2+ + 2e2, 8, 2 2,8
Chlorine (atomic number 17 ) has 7 electrons in the valence shell. It has a
tendency to gain one electron to complete its octet.
+ e-
Cl
2,8,7
Cl2,8,8
Thus, when magnesium and chlorine are brought together, the magnesium atom
transfers its two valence electrons to two chlorine atoms. In the process both the
atoms acquire the stable electronic configuration of nearest inert gases. The
positively charged magnesium ion Mg2+ and negatively charged Chloride ions
(Cl-) are now held together by the electrostatic force of attraction.
‾
Mg2+ + 2 Cl-
Mg2+ 2 Cl- or MgCl2
This process can also be shown as below
(Mg 2+) [
Mg
x
x
]2
Q. 10. What is the difference between alloy & amalgam? Write the composition
of brass & bronze. Write 2 properties of alloy.
(5)
Ans. (a) Alloy – It is a homogeneous mixture of 2 or more metals or a metal
and a non-metal.
Amalgam – If in an alloy one of the metals is mercury, then the alloy is
an amalgam.
(b)
Brass – Alloy of Copper and Zinc.
Bronze – Alloy of Copper and tin.
(c)
Properties of alloy – (i) The electrical conductivity and melting point of
an alloy is
less than that of pure metal.
(ii)
Alloy does not corrode easily.
CHAPTER-4
Carbon and its Compounds
Q1. What is denatured alcohol?
(1)
Ans:- Ethane is made unfit for drinking by adding poisonous substances like methane to it.
Dyes are also added to colour the alcohol blue so that it can be identified easily. This is called
denatured alcohol.
Q2. Name the product other than water formed on burning of ethanol in air?
Ans:- Carbon dioxide gas.
(1)
Q3. Give the names of the functional groups:
a)
CHO
b)
C
||
Ans:- a) Aldehyde
b) Ketone.
(1)
Q4. Why carbon forms compounds by sharing of electrons and not by formation of ions? ( 2)
Ans:- Carbon is tetravalent in nature. If it gains 4 electrons to form C 4- ions, then it will be
difficult for 6 protons to hold on to 10 electrons.
To lose 4 electrons forming C4 + ion, it would require a large amount of energy to remove
4 electrons. Hence it forms bond by sharing of electrons.
Q5.Allotropy is a property shown by which class of substances: elements, compounds or
mixtures? Give one example of allotropy.
( 2)
Ans. Elements show allotropy. For example, graphite, diamond and fullerenes are allotropic
forms of carbon.
Q6. Under what conditions can a saturated hydrocarbon produce a sooty flame?
(2)
Ans. Saturated hydrocarbon produce sooty flame only when burnt in limited supply of
oxygen.Due to limited supply of oxygen, the incomplete combustion of the hydrocarbon
takes place resulting in unburnt carbon producing sooty flame.
Q7.a) Draw the structure for the following compounds:
i) Propanoic acid.
ii) Butanal
b) Why is conversion of ethanol acid considered as oxidation reaction?
ANS. a)
H
H
H
O
|
|
||
C
C
C
|
|
H
H
OH
Propanoic acid
H
H
|
C
H
|
C
H
|
C
H
|
C=0
(3)
|
|
|
H
H
H
Butanal
b) Ethanol is oxidised with alkaline potassium permanganate to form ethanoic acid. As the
addition of oxygen takes place,therefore it is called oxidation reaction.
Q8. What happens when an ester is heated with a base such as sodium hydroxide? Write
equation of the reaction which takes place? What is the special name for this reaction and for
what purpose it is used?
(3)
Ans. When an ester is heated with sodium hydroxide solution then the ester gets hydrolysed
to form the parent alcohol and sodium salt of the carboxylic acid .
Example---When ethyl ethanoate ester is boiled with sodium hydroxide solution, then sodium
eyhanoate and ethanol are produced.
CH3COOC2H5 + NaOH ---------CH3COONa + C2H5OH
Sodium
Ethanol
Ethanoate
The alkaline hydrolysis of esters is known as saponification (soap making).This is because of
the fact that this reaction is used for the preparation of soaps. When the esters of higher fatty
acids with glycerol (oils and fats) are hydrolysed with sodium hydroxide solution,we get
sodium salt of higher fatty acids which are called soaps.
.
Q9
a)What is the difference between soap and detergent in chemical composition ?
b)Why detergent remains effective in hard water while soap not for cleaning?
c)Explain the mechanism of the cleaning action of soap.
(5)
Answer:- a) Soap:- It is sodium or potassium salts of long chain carboxylic acid.
Detergent:- It is ammonium or sulphonate salts of long chain carboxylic acids.
b) Soap reacts with calcium and magnesium chloride or sulphate which causes
hardness of water to form an insoluble substance (scum). The charged ends of detergents
donot form insoluble precipitates with the calcium and magnesium ions in hard water. Thus,
they remain effective in hardwater.
c) Most dirt is oily in nature. Oil does not dissolve in water. The molecule of soap
has two ends with differing properties. The ionic-end of soap dissolves in water while the
carbon chain dissolves in oil. The soap molecules, thus form structures called micelles where
one end of the molecule is towards the oil droplet while the ionic end faces outside. This
forms an emulsion in water. The soap micelles thus helps in dissolving the dirt in water and
we can wash our clothes clean.
10) Write the chemical equation for the following reaction:
a) Ethanoic acid with Sodium Carbonate
b) Ethanoic acid with Sodium Bicarbonate
c)Burning of Ethanol
d)Ethanoic acid with Sodiun Hydroxide
e) Heating Ethanol at 443K with excess concentrated sulphuric acid
Anwser:- a)2CH3COOH + Na2Co3
2CH3COONa + H2O + CO2
(5)
b) CH3COOH + NaHCO3
c)CH3CH2OH + O2
d) NaOH + CH3COOH
CH3COONa + H2O + CO2
CO2 + H2O + heat and light
CH3 COONa + H2O
Hot conc.
e) CH3 CH2OH
CH2 = CH2 + H2O
H2SO4
5.
PERIODIC
ELEMENTS
CLASSIFICATION
OF
Q.1.What were the criteria used by Mendeleyev in creating his
periodic table?
Ans.In
creating his periodic table, Mendeleev was guided by two
factors:(a). Increasing atomic masses and;
(b) Grouping together of elements having similar properties.
Q.2.Besides Gallium, which other elements have since been
discovered that fill the gaps left by Mendeleev in this periodic
table?
Ans.Scandium and Germanium.
Q.3.Name two elements you would expect to show same kind of
chemical reactivity as Magnesium. What is your best choice?
Ans.Beryllium, Calcium and Strontium will show same kind of
chemical reactivity as Magnesium because they are placed in the same
group. Elements placed in the same group have similar outer
electronic configuration.
Q.4.Looking at the resemblance of Hydrogen to alkali metals and
the Halogen family, to which group and period should Hydrogen
be assigned in Mendeleev’s periodic table?
Ans.Since properties of Hydrogen resemble both alkali metals and
Halogens, it can be placed either in group IA or group VII A. Since
Hydrogen has the lowest atomic mass, it is placed in period I.
Q.5.An atom has electronic configuration 2, 8, 7.
(a) What is the atomic number of this element?
(b) To which of the following elements would it be
chemically similar:(i) 7N
(ii) 9F
(iii)15P
(iv)18Ar
Ans. (a) The atomic number of the element is 2+ 8+7=17.
(b) Electronic configurations of the given elements are:(i)N-2,5.
(ii)F-2,7.
(iii)P-2,8,5.
(iv)Ar-2,8,8.
Thus F having similar electronic configuration with 7 valence
electrons would be chemically similar to the given element.
Q.6.The positions of three elements A, B, C in the periodic table
are show below:Group 16
Group 17
A
B
C
(a) State whether C is a metal or non-metal.
(b) State whether C is more reactive or less reactive than A.
(c) Will C be larger or smaller than B in size?
(c) Which type of ion (cation or anion) will be formed by element
A?
Ans.(a) Elements of group 17 have 7 electrons in their respective
valence shell and have a strong tendency to gain an electron to
complete their octet. So, A is a non-metal.
(b) On moving down a group, the atomic size increases and thus the
force of attraction of the nucleus for the incoming electrons decreases.
Hence the reactivity decreases. Therefore C is less reactive than A.
(c) B and C belong to the same period. On going from left to right in a
period the nuclear charge increases but the number of shells remain
same. Therefore atomic size decreases from left to right. Thus C is
smaller in size than B.
Q.7.Use Mendeleev’s periodic table to predict the formulae for
the oxides of K, C, Al, Si and Ba.
Ans.K2O, CO2, Al2O3, SiO2, BaO.
Q.8.A metal M forms an oxide having the formula M2O3. It
belongs to third period of the modern periodic table. Give its
atomic number and valency.
Ans.Atomic number of the element is 2, 8, 3=13 and its valency is 3.
Q.9.What are the uses of Modern Periodic table?
Ans.In modern periodic table, the elements with similar properties are
placed together in the same group. If we know the properties of one
element of the group, the properties of other elements of the group
can be predicted. Thus it makes the study of elements systematic.
Q.10.Why is long form periodic table regarded better than
Mendeleev’s periodic table?
Ans.It is due to the following reasons:-
(a)It is based on atomic number.
(b) There is no confusion regarding the position of isotopes.
(c)All groups are independent and there are no sub-groups.
(d) It is more systematic.
Chapter 6
Life Processes
VSA Question carrying 1 marks each
Q1. What are the main two types of nutrition?
Ans. Autotrophic and Hetrotrophic nutrition.
Q2. what does the word ‘Sapro’ mean?
Ans. The word Sapro means rotten.
Q3. What is the process of obtaining food in Amoeba called?
Ans. The process of obtaining food in Amoeba is called Phagocytes.
Q4. name the cellular organelles where the folloing processes take place (i) Photo synthesis
(ii) Cellular aerobic respiration?
Ans. (i) Chloroplast (ii) Mitochondria.
Q5. What is the function of bile?
Ans. Bile brings about the emulsification of fats.
Q6. Where are hormones synthesized in plants?
Ans. In planyts hormones are synthesized in the shoot and root tips.
Q7. Name the largest artery in our body?
Ans. Aorta
Q8. What is the liquid part of blood called?
Ans. Plasma.
SAQ carrying 2 marks each.
Q1. What is emulsification?
Ans. Breakdown of the large fat droplets into smaller ones.
Q2. Why are plants green?
Ans. Plants posses green chloplastic pigments called chlorophyll which absorb most of the
blue and red regions of the incident light. They reflect green light so the plants look green in
colours.
Q3. State the function of epiglottis?
Ans. Epiglottis is a leaf like cartilaginous flap present at the anterior end of glottis. It closes
the glottis during swallowing to check the entry of food into glottis.
Q4. In which form is (i) Carbohydrates stored in plants (ii)Food stored in animals.
Ans. (i) Carbohydrates are stored in the form of starch in plants.
(ii) In animals food is stored in the form of glycogen.
Q5. What is breathing?
Ans. It is aphysical process of inhalation or bringing in fresh air for obtaining oxygen and
exhalation or taking out of foul air for elimination of CO2.
SAQ carrying 3 marks each.
Q1. Why are white blood corpulses called “Soldiers” of the body?
Ans. White blood corpulses are called soldiers of the body because they protect the body
from infections by destroying foreign matter. They also manufacture antibodies which are
responsible for immunity.
Q2. What happens to glucose which enters nephron along with filtrate during excretion in
human beings. State two vital functions of kidney.
Ans. Glucose is reabsorbed in tubule.
Vital functions of kidney (i) Excreation, separation of nitrogenous wastes for elimination.
(ii) Osmoregulation, maintainance of balance of water and salts in the body through
elimination if extra and retention if deficient.
Q3. When is blood clotting useful?
Ans. Cloting of blood is useful phenomenon to stop flowing of blood (bleeding) during cuts
and accidents and at the time of accidents.
Q4. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and
birds?
Ans. Mammals and birds are warm blooded animals. They continiously use energy to
maintain treir body temperature. They have a higher energy need and require more
oxygenated blood for their cells. It is important that their oxygenated blood doesnot mixup
with deoxygenated blood.
Long Answer Question carrying 5 marks.
Q1. Name the blood vessel that brings deoxygenated blood to the human heart (b) Which
chamber of human heart receives oxygenated blood (c) Explain how oxygenated blood from
this chamber is sent to all parts of the body?
Ans. (a) Pulmonary vein.
(b) Left arterium.
(c) After receiving the deoxygenated blood, the atium contract during this countraction the
deoxygenated blood of the right atium is poured into the right ventricle. Then the ventricle
contract and the deoxygenated blood flows to the lungs through pulmonary artery.
CHAPTER 7
CONTROL
AND
COORDINATION
Q1 Which gland secretes the growth hormone?
Ans Pituitary gland (anterior lobe of pituitary).
(1)
Q2 Name the part of the hindbrain which is responsible for maintaining the posture and
balance of the body.
(1)
Ans Cerebellum.
Q3
Which hormone is responsible for the development of moustache and beard
in man ?
Ans Testosterone
Q4 Why is the use of iodised salt advisable ?
(2)
Ans Iodine is essential for the synthesis of thyroxin hormone in the thyroid gland.
Thyroxin regulates carbohydrates , protein and fat metabolism in the body so
.
as to provide the best balance for growth .In case of deficiency of iodine in
our diet , there is a possibility that we might suffer from goitre . Thus , use
of iodised salt is advisable to prevent iodine deficiency in the body .
Q5 Why are diabetic patients advised to take less sugar in their diet by the
doctor ?
(2)
Ans Insulin hormone is secreted by the pancreas which helps in regulating blood
sugar level in our body .It is not secreted in proper amount in the body of
the diabetic patient. If the sugar level in the blood rises , it causes many
harmful effects . So the diabetic patients are advised to take less sugar .
Q6. What happens at the synapse between two neurons ?
(2)
Ans. The information acquired at the end of the dendrite tip of a nerve cell sets
of a chemical reaction that creates an electrical impulse This impulse travels from
the dendrite to the cell body , and then along the axon to its end .At
the end of the axon , the electrical impulse sets off the release of some
chemicals . These chemicals cross the gap or synapse and start a similar
electrical impulse in a dendrite of the next neuron .
Q7. What is the difference between sensory and motor neurons? Which part of the brain
is responsible for auditory reception and sensation of smell?
(3)
Ans. Sensory neurons-These are the neurons that transmit impulses towards the central
nervous system (brain and spinal chord) through their axons.
Motor neurons- These are the neurons that transmit impulses from central nervous
system towards effectors (muscles or glands).
Specific part of brain is responsible for auditory reception and smell.
Q8
Draw a human brain and label its different parts?
(3)
Ans Text book page no.118 & fig.7.3.
Q9
What is a reflex action? Explain with help of an example. Draw a labeled diagram
to show the reflex action?
(5)
Ans a) Reflex action is spontaneous & involuntary response of effectors (muscles &
glands) to stimulus. It is extremely quick action that does not involve any thinking
by the brain.
b)
When our hand accidentally touches the hot object, heat is sensed by the thermo
receptors present in the skin of hand. The receptor triggers nerve impulse in sensory
neuron. It transmits message to spinal cord. In spinal cord impulse is passed on to the relay
neuron which ,in turn passes it to the motor neuron. The motor neuron transmits the
instruction to a muscle in our arm. The arm muscles contract and pulls our hand away
from the hot object.
c)
Text book page no.117 fig7.2
Q10. a)How is the movement of leaves of a sensitive plant different from the movement of
the shoot towards light?
5)
b)Name one plant hormone that promotes growth in plant and one plant hormone that
inhibits growth?
c)How does phototropism occur in stem?
Ans a)
The movement of leaves of a sensitive plant is neither towards nor away from
stimulus like touch. While movement of shoot is towards stimulus like light .The movement
of leaves of a sensitive plant is not directional while the movement of shoot is directional.
b)
Plant hormone that promotes growth in plants-Auxin
Plant hormone that inhibits growth-Abscisic acid.
c)
The movement of a plant part in response to light is called phototropism.
The shoot responds by bending towards light while roots respond by bending away from
the light. We know that the plant stem responds to light and bends towards it due the action
of auxin hormone.This happens as follows:
i)
When sunlight comes from above, then the auxin hormone present in the tip of the
stem spreads uniformly down the stem .Due to the equal presence of auxin, both
the sides of the stem grow straight and with some rapidity.
ii)
When the light falls on the right side of the plant, then the auxin hormone collects
in the left side of the stem, away from the light. This is because auxin hormone
prefers to stay in shade.
Thus more auxin hormone is present in the left side of the stem as compared to the right. The
left side of stem, hence grows faster than its right side and therefore, the stem bends towards
the right side (direction of light).
8.
Q1 Name any two sexually transmitted diseases?
Ans: 1] Gonorrhoea 2] syphilis
Q2 Write full form of IUCD and AIDS?
Ans: IUCD-Intra Uterine Contraceptive Device.
AIDS-Acquired Immuno Deficiency syndrome.
Q3 Where does fertilization take place in human
female?
Ans: Fertilization takes place inside the fallopian tubes.
Q4 If a women is using Copper-T, will it help her in
protecting sexually transmitted diseases?
Ans: Copper-T prevents fertilization but the chances of
infection persist. So, Copper-T will not help her in protection
against sexually transmitted diseases.
Q5 What are the advantages of sexual reproduction
over asexual reproduction?
Ans: Due to reshuffling of chromosomes and crossing over,
sexual reproduction brings about variation in almost all
characters so that no two individuals are similar. Genetic
changes contribute to evolution of species to form better
organisms. Asexual reproduction does not contribute to
evolution of species as there is no variation.
Q6 Why is vegetative propagation practiced for
growing some type of plants?
Ans: Vegetative propagation is practiced in some plants
because1. It is the only method of reproduction in seedless plants.
2. A full matured plant is obtained in a very short time.
3. It helps to preserve the characters of the plant the breeder
desires.
4. It is an easy and economical method for multiplication of
ornamental plants.
Q7 How does reproduction helps in providing
stability to population of species?
Ans: Reproduction helps in providing stability to population
by1. Introducing variation in the population through genetic
combination that helps the population to tide over
adverse environmental conditions and adapt to changing
environment.
2. Balancing birth and death rate.
Q8 What could be the reasons for adopting
contraceptive methods?
Ans: Contraceptive methods are adopted for the following
purposes1. To avoid frequent and unwanted pregnancies.
2. To maintain good reproduction health.
3. To obtain protection from sexually transmitted diseases.
4. To restrict the number of children.
Q9
Differentiate
menopause?
between
menarche
and
Ans- Commencement of menstruation at puberty in human
female is termed menarche and its stoppage at the age of
50yrs is called menopause.
Q10 What is the importance of DNA copying in
reproduction?
Ans-DNA copying is an important phenomenon of
reproduction through which the organisms pass their features
to their offsprings. It maintains the genetic pool and the body
design features in different generation of the species. DNA
copying also produces variations due to genetic linkage and
crossing over of chromosomes. Such variations are useful for
the survival of species.
9.
Q1:-Give examples of two variations found in humans.
Ans: - 1. Human height
2. Free earlobe and attached earlobe
Q2:- Write the names of the components of DNA?
Ans: - Components of DNA are nucleotides. Each nucleotide has
further three components1. Deoxyribose sugar
2. A nitrogenous base
3. A phosphate group
Q3:-Give two examples where environmental factors govern sexdetermination?
Ans: - a) In turtle, high incubation temperature results in the
development of female progeny.
b) In lizard high incubation temperature results in male progeny.
Q4:- What is genetic engineering? Give the full form of GMO.
Ans: - It is the technique of altering the genetic make up of an
organism by inserting gene (or segment of DNA) from other organism
into its DNA.
The full form of GMO is GENETICALLY MODIFIED ORGANISM.
Q5:- How are the areas of study – evolution and classification
interlinked?
Ans:-Classification of organisms is based on relative similarities and
differences among organisms. Resemblances in organisms are
because they have arisen from a common ancestor and differences are
due to adaptations to different types of environment. As the organisms
can be graded in order of increasing complexity, it indicates the
concept evolution.
Q6:-Why are small numbers of surviving tigers a cause worry
from the point of view from genetics?
Ans: - With decreasing number of tigers, their genetic pool is also
vanishing which is essential to maintain the ecological and food chain
balance.
Q7: - Will geological isolation be a major factor in the speciation
of an organism that reproduces asexually? Why or Why not?
Ans: -During asexual reproduction organisms undergo a little
variation over generations .The variation in the genetic pool are not
enough to raise a new species .Thus, any change resulting from
geographical isolation may not be passed to the next generation.
Q7: -A man with blood group ‘A’ marries a women blood group
‘O’ and their daughter has blood group ‘O’. Is this information
enough to tell you which of the traits –blood group ‘A’ or ‘O’ is
dominant? Why or Why not?
Ans: - Blood group ‘A’ is dominant while ‘O’ is recessive character.
If a man with blood group ‘A’ marries a woman with blood group ‘O’
and their daughter has blood group ‘O’ , then the man has one copy
of ‘A’ and one copy of ‘O’ blood group.
Q8: - Differentiate between autosomes and sex chromosomes.
Ans: - 1. The pair of chromosomes that are responsible for
development of body characters are called autosomes .In human body,
there 22 pairs of autosomes.
2.The pair of chromosomes which are responsible for determining the
sex of the individual called sex chromosomes .
Q9: -Why Mendel selected garden pea plant for his experiment.
Ans: - Mendel selected garden pea plant for his experiment because1. Pure varieties of pea were available.
2. Pea plants showed a number of easily detectable contrasting
characters.
3. The flower structure of pea is such that it allows controlled
breeding.
4. Pea flower normally remains closed and undergoes self pollination.
Q10:-How is the equal genetic contribution of male and female
parents ensured in the progeny?
Ans:-The gametes responsible for the formation of progeny develop
by the process of meiosis. During meiosis only one set of
chromosomes (50% of Gene) is transferred to the gamete. When male
and female gametes fuse, one set of chromosome from each parent
cell come together and complete the genetic pool.So, progeny
receives 50% genetic contribution through each gamete(male and
female).
10.LIGHT – REFLECTION AND REFRATION
Q1:- Define 1 dioptre of power of lens?
Ans: - One dioptre is the power of a lens of focal length one
metre.
Q2:- Why do you prefer convex mirror as a rear-view mirror
in vehicles?
Ans: - A convex mirror produces an erect and highly diminished
image of the objects.Further, since it is curved outwards; it
gives a wider field of view.
Q3:- The refractive index of diamond is 2.42.What is the
meaning of the statement?
Ans: - It means that light travels 2.42 times faster in vacuum
than in diamond.
Q4:- One half of a convex lens is covered with a black
paper. Will this lens produce a complete image of that
object? Verify your answer experimentally. Explain your
observation.
Ans:- Yes ,it will produce a complete image of the object.
This can be verified experimentally by observing the image of
the distant object like tree on a screen when lower half of the
lens is covered with a black paper. However, the brightness of
the image gets reduced.
Q5:- How can you distinguish between a convex mirror, a
plane mirror and concave mirror?
Ans: - With the help of virtual image of three mirrors, we can
distinguish between three mirrorsa) Plane mirrors will produce virtual image of the same size.
b) Concave mirrors will produce magnified virtual image.
c) Convex mirror will produce a diminished virtual image.
Q6:- The magnification produced by a plane mirror is
+1.What does this mean?
Ans:- m = h’/h=1
Therefore, h’ = h
i.e, the size of the image is equal to the size of the object. +ve
sign of m indicates that the image is virtual.
Q7:- Calculate the distance at which an object should be
place in front of a thin convex lens of focal length 10cm to
obtain a virtual image of double its size?
Ans:- f = +10cm
m = +2 (as the image is virtual)
As, m = v/u = 2
Or,
V = 2u
1
As, /v -1/u = 1/f
Or, 1/2u - 1/u = 1/10
Or, - 1/2u = 1/10
Therefore u = -5cm
The object should be place at a distance of -5cm from the lens.
Q8:- A concave mirror of focal length 20cm is to be used
as a shaving mirror. Which of the following is the suitable
object distance from the mirror? Justify your answer.
a) 10cm
b) 20cm
c) 30cm
Ans:- For using concave mirror as shaving mirror, u<f .So, the
object distance can only be 10cm
Q9:-Light enters from air into diamond. Which has a
refractive index of 2.42? Calculate the speed of light in
diamond. (The speed of light in air is 3 x 108 m/s)
Ans:As, n = c/v
V = c/n
= 3 x (10)8/2.42
= 1.24 x 108 m/s
Q10:- A concave mirror of focal length 15cm forms an
image of an object kept at a distance of 10cm from the
mirror. Find the position, nature and size of the image
formed by it.
Ans:- Here ,
f = -15cm
u=-10cm
v=?
1
/v= 1/f -1/u
(mirror formula)
1
1
-1
/v= / (-15) / (-10)
= 1/10 – 1/15
= 3/30 -2/30
=1/30
Therefore, v = 30cm
Thus, the image is formed at 30cm from the mirror.
As, v is positive, the image is virtual and erect
As, m = -v/u
= - 30/ (-10)
=3
Therefore, the size of the image is three times the size of the
object.
11.HUMAN EYE AND COLOURFUL WORLD
Q1:- Name the optical phenomenon responsible for
formation of RAINBOW?
Ans:- Refraction, internal reflection and dispersion of light.
Q2:- What is meant by scattering of light?
Ans:-Scattering is the bouncing off of electro-magnetic
radiations by atoms and molecules of the medium through
which they are propagating.
Q3:- Why different colours deviate through different angles
on passing through a prism?
Ans:- This is because different colours have different
wavelengths and glass has different refractive index for
different wavelengths .
Q4:-Which phenomenon of vision is used in
cinematography?
Ans:-Persistence of vision.
Q5:- The near point of the hypermetropic eye is
1metre.What is the power of the lens required to correct
this defect. Assume that near point of the normal eye is
25cm.
Ans: - Since, the near point of the hypermetropic eye is1m
(100cm), the lens used should be such that the rays of light
starting from normal near point(25cm) appear to come from the
near point of hypermetropic eye.
Thus,
u = -25cm
v =-100cm
1
1
/f = /v -1/u
f = uv/u-v
= (-25) x (-100)/ (-25) – (-100)
=100/3
=33.3cm
P = 100/f
= 100/33.3
=3D
Since the power is positive , lens must be convex.
Q6:-The far point of a myopic person is 80cm in front of the
eye. What is the nature and power of the lens required to
correct the problem?
Ans:- Distance of far point ,x =80cm
P =?
For viewing distant objects, focal length of the corrective
lens
f = - x = -80cm
P = 100/f
= 100/-80
=-1.25 D
The Lens is concave.
Q7:- Danger Signals are red in colour, why?
Ans:-Due to its longer wavelength, red colour is least scattered
by fog or smoke.Thus, the red is visible in the same colour from
large distances.
Q.8.Why do we have two eyes for vision and not just one?
Ans. (a) It gives a wider field of view.
(b).The ability to detect faint objects is enhanced with two eyes
instead of one.
(c). Our eyes are separated by a few centimeters; each eye sees a
slightly different image. Our brain combines the two images into one
and thus provides a three-dimensional perception of the objects.
Q.9.What is persistence of vision?
Ans.The ability of an eye to continue to see the image of an object for
a very short duration even after the removal of the object is called
persistence of the vision. In human eye, vision persists for 1/16 th of a
second after removal of the object.
Chapter 12
Electricity
V.S.A Question (1 mark each)
1. What is the resistance of an ideal voltmeter and an ammeter?
Ans. Infinite and zero.
2. What is the value of charge on an electron in coulomb?
Ans. -1.6 x 10-19
3. Why is resistance more in combination of resistors?
Ans. In series combination of resistors, the effective length of the conducting path
increases and as such resistance increases (R ∞l)
4. Name two special characters of a heater coil?
Ans. A heater coil should have (i) high resistivity (ii) high melting point.
5. What is the resistance of a connecting wire?
Ans. It is negligible, almost zero.
S.A.Q (2 marks each)
1. What is the difference between a resistor and resistance?
Ans. A resistor is an object where as resistance is its property due to which it obstructs the
flow of
electrons through it.
2. Electric current is flowing through a wire from west to east direction. What is the
direction of motion of the conductor electrons in the wire?
Ans. From east to west as direction of electric current is opposite to the direction of flow
of conduction electrons.
3. Why are the conductors of electric heating devices such as toasters and electric irons)
made of an alloy rather than a pure metal?
Ans. It is because alloy is less affected by the rise in temperature than a pure metal. In
other words alloys do not oxidise (or burn) easily at high temperature.
4. What will be the equivalent resistance R of two resistors R1 and R2 (i) connected in
series and (ii) connected in parallel?
Ans. When connected in series
R=R1+R2
When connected in parallel
1/R=1/R1+1/R2 or R=(R1R2) /(R1+R2)
5. What will happen to current if the voltage across the circuit reduces to half its original
value while the resistance of the circuit remains constant?
Ans. Current=Voltage/Resistance
If voltage becomes half its original value, the resistance remains the same, then current in
the circuit will be reduced to half its original value.
SAQ (3 marks each)
1. A wire of resistance 5 ohm is bent in the form of a closed circle. What is the effective
resistance between the two points at the ends of any diameter of the circle?
Ans. The length of the wire between two points at the ends of a diameter of a circle is half
of the whole wire. The resistance of a conductor is directly proportional to its length.
Thus, the two resistance 5/2 Ω will be in parallel.
Let R be the effective resistance.
1/R=2/5+2/5
1/R=4/5
R=5/4=1.25 Ω
2. Calculate the effective resistance in the diagram given.
Ans. In this case resistance DA and AB are in series. DC and CB are also in series. But
AD and AB together are in parallel to DC and CB together.
Thus, Resistance (DA + AB)=1+1=2Ω
and Resistance (DC + AB)=1+1=2Ω
Let Rp be the effective resistance, then (by parallel formula)
1/Rp=1/2+1/2
=(1+1)/2=2/2
Rp=1Ω
Thus, the combination has a resistance of 1 ohm.
3. Why does resistance of a conductor increase with increase in temperature?
Ans. When a metallic is heated the atoms in the metal vibrate with greater amplitude and
frequency due to increase in temperature the thermal velocities of free electrons also
increase. Therefore the numbers of collisions between free electrons and atoms increase.
This increases the resistance of the conductor.
4. Why is it not advisable to handle electrical circuit with wet hands?
Ans. The resistance of dry skin human body is about 50,000Ω. When the skin is wet, the
resistance is lowered to about 10,000Ω. If a person with wet hand touches the electrical
circuit the current will flow suddenly due to less resistance. Therefore, it is advisable not
to touch the electrical circuit with wet hands.
Long Answer Question (5 marks)
1. A dry cell should be used intermittently and not continuously. Explain why?
Ans. Hydrogen gas in the formed during the working of the dry cell. This gas in the form
of bubbles forms an insulated layer around the carbon rod (i.e anode). As a result of this,
the resistance of the cell is increased and hence the flow of charges in the cell is opposed.
Ultimately, the dry cell stops working if used continuously. However, these bubbles of
hydrogen gas are removed slowly by Mno2, which acts depolarizers. The dry cell can
work if the bubbles of hydrogen gas around carbon rod are completely removed by Mno2.
For this purpose time is required. So the dry cell should be used intermittently to provide
sufficient time for the removal of hydrogen gas bubbles by manganese dioxide.
13.Magnetic effect of electric current
V.S.A.Q (1 marks)
1.
What constitute the field of a magnet?
Ans. The space around a magnet within which its magnetic effect can be experienced,
constitutes the (magnetic) field of the magnet.
2. What is meant by the following? A fuse is rated at 8 A?
Ans. It means that it burn if current exceeds 8A.
3. What is short circuiting in an electric supply?
Ans. Short circuiting in an electric supply occurs when the live wire touches the neutral
wire.
4. What happens when a current carrying conductor is kept in a magnetic field?
Ans. It experience a force.
5. Are magnetic field lines open or closed curves?
Ans. They are closed curves.
6. What is the frequency of AC in India?
Ans. It is 50 Hz.
SAQ (2 marks)
1. Write down any two properties of magnetic field lines.
Ans. 1 It is directed from north pole to south-pole outside the magnet and inside the
magnet it is vice-versa.
2.Two magnetic field lines never intersect each other.
2. What is electro-magnetic induction?
Ans. In reality it is the conversion of mechanical energy into electrical energy.
3.What is the role of each of the three pins in a power plug?
Ans. The thick pin at the top of a power plug is for earthing ,the live pin is on the left and
the neutral pin is on the right of the power plug.
4. what are the two main precautions to be the taken while using an electric supply?
Ans. (i)Electric supply should be immediately switched off from the main switch in case
a person touches a live wire or if there is a fire in the house.
(ii) Electric supply should also be switched off during natural calamities like
earthquake, floods etc.
5. What is the difference between two circuits used in household electricity?
Ans. One of 15 ampere rating is used for higher power appliances and second of 5 ampere
rating is used for bulbs, fans, etc. which are of lower power rating.
6. Two wires A and B suspended. These wires are connected in parallel with a battery as
shown in figure. Will the distance of separation between the wires (i) remains the
same or (ii) increases or (iii) decreases? Explain.
Ans. When wires are connected to battery in parallel, then the current in both the wires
will attract each other, therefore the distance between the wire decreases.
SAQ (3 marks)
1. A circuit has a fuser of 5 A. What is the maximum number of 100 watt (220v) bulbs
this can be safely used in the circuit?
Ans. Suppose x number of such bulbs can be used.
Power of one bulb =100 watt
Power of x bulb (p)=100 x X watts
Potential difference(v)=220 volts.
I=5 ampere
P=VI
= 100 x X= 220x5
X =220x5/100=11 bulbs
2. On what factors does the force experienced by a current carrying conductor placed in
a uniform magnetic field depend?
Ans. The place in a uniform magnetic field depends on :(i)
The length of the conductors(l).
(ii)
The magnitude of current flowing through the conductor (l), and
(iii) The magnitude of the magnetic field of the conductor (B)
3. A fixed wire AB carries current I. An electron is moving parallel to the wire in which
direction does the electron tend to move?
Ans. By right hand thumb rule, the magnetic field in the vicinity of wire is downward,
perpendicular to the plane of the paper. The conventional direction of electrical current
his opposite to the direction of motion of electron. By Fleming left hand rule the force on
electron is always away from wire in the plane of paper; therefore, the electron will be
deflected downward (away from the wire) in the plane of paper.
4. A cylindrical bar magnet is kept along the axis of a circular coil. Will there be a
current induced in the coil if the magnet is rotated about the axis?
Ans. The magnetic field of a cylindrical magnet his symmetrical about the axis. As the
magnet is placed along the axis of circular coil, there will be no induced current because
the magnetic flux linked with the coil does not change due to rotation of the magnet.
LAQ (5 marks)
1. Answer the following
i.
What is the phenomenon of electron magnetic induction?
ii.
Which is the device used for producing current?
iii.
What is the essential difference between AC generator and a DC generator?
iv.
At the time short circuit, what happens to the current in the circuit?
v.
Give the role of split ring in AC generator?
Ans. i) the phenomenon of electromagnetic induction is producing induced current in a coil
due to relative motion between a magnet and the coil.
ii) The device used for producing current is generator
iii) The essential difference between an AC generator and DC generator is that AC
generator has slip rings while the DC generator has a commutator.
iv)
At the time of short circuit, the current in the circuit increases heavily.
v)
The role of split ring is to reverse the direction of current through a circuit.
14.Sources of Energy
VSAQ (1 marks)
1. Name the two forms of energy usually at our homes?
Ans. Heat and electricity
2. Exposure to which component of solar radiation could be a health hazard?
And. Ultra violet radiation.
3. Name two forms in which solar energy manifests itself in oceans?
Ans. Tidal energy and ocean thermal energy
4. What are the sources of energy in nuclear fission and fusion?
Ans. The disappearance of certain mass (
m) in both the processes, fission and fusion.
It appears as energy.
5. Which radiations of sunlight are used in heating a solar cooker?
Ans. Infra red radiations.
6. Name any two renewable sources of energy?
Ans. Solar energy and Geo-Thermal energy.
SAQ(2 marks)
1. Give any two peaceful uses of nuclear energy.
Ans. Nuclear energy can be used:
(i)
for generating electricity
(ii)
in the treatment of cancer
2. How is electrical energy obtained from nuclear reactors?
Ans.The large amount of heat produced during nuclear fission is treated to convert into
steam. The steam is then used to drive turbines which are connected to electrical
generators which convert it into electrical energy.
3. What is the purpose of glass sheet in solar heating devices?
Ans. Glass sheet has a property that permit the infra-red radiations of short wave length
from the sun to get into heating device but does not allow IR radiations of longer wave
length to leave the solar heating device.
4. Why is the use of charcoal discouraged although it is a better fuel than coal?
Ans. Because charcoal is prepared from destructive distillation of wood. So, for this
purpose more and more trees would have to be cut down which causes deforestation. It
affects the ecological balance of earth.
5. Can any source of energy be pollution free? Why or why not?
Ans. No source of energy can be perfectly pollution free but biomass energy,
hydroenergy, wind energy, geothermal energy and solar energy is almost pollution free. If
fossil fuel is allowed to burn in presence of excess of oxygen the pollution produced can
be much reduced.
SAQ (3 marks)
1. If you could use any source energy for heating your food, which one would you use
and why?
Ans. Fuel to be used should be easily accessible, should be easy to store and transport and
should be economical. If we are in city area, LPG should be used since it does not
produce pollution, is easily available and is economical.
In rural area, gobar gas or biogas should be used. It is almost free, has high calorific value
and is pollution free. It is also renewable source of energy.
2. What is Bio-energy?
Ans. Bio-energy is the energy generated by biomass. Energy may be in form of fire, fuel
oil, biogas, animal dung alcohol, charcoal or even human excreta. Fuels are derived from
bio-mass. It is an indirect source of solar energy and is renewable source of energy.
3. Hydrogen gas has been used as a rocket fuel. Would you consider it a cleaner fuel
than CNG. Why or why not?
Ans. The by-product of hydrogen when used as a fuel and burnt is water while that of
CNG are water and carbon dioxide gas. Water is an absolutely harmless by-product,
however carbon dioxide in the environment causes green house effect leading to global
warming. Hence, hydrogen can be called a cleaner fuel than CNG.
4. “Only a small part of the solar energy that strikes the upper regions of atmosphere,
reaches the surface of the earth”. Discuss?
Ans. When the solar energy falls in the top surface of the atmosphere then some solar
energy is reflected back into the space by the atmosphere, and the atmosphere also
absorbs a lot of solar energy, for example most of the ultra violet rays are absorbed by the
ozone layer. So the solar energy which reaches on the earth’s atmosphere is mainly in the
form of heat rays (infrared rays) and visible light, which is a small part of the solar
energy.
5. What is geo-thermal energy? What are its limitations?
Ans. Geo-thermal energy is the heat of the earth and is the naturally occurring thermal
energy found within rock formations and the fluids held within those formations. Geothermal energy is on of those few sources that do not come directly or indirectly from the
solar energy.
Limitations
i)
Goe-thermal hot spots are scattered and usually some distance away from the
areas that need energy.
ii)
The overall power production has lower efficiency (about 15%) as compared to
that of fossil fuels (35% to 40%)
iii)
Though as a whole geothermal energy is inexhaustible, a single bore has a limited
life span of about 10 yrs.
iv)
Noise pollution is caused by drilling operations at geo-thermal sites.
LAQ (5marks)
1.
What are environment consequences of the increasing demand for energy? What
steps would you suggest to reduce energy consumption?
Ans. The demand of energy consumption is increasing day to day. Exploiting any source
energy may disturb the environment in one-way or other. For example getting energy
from fossil fuel may cause lot of pollution in air. Getting energy from nuclear fission may
create problem of disposal of nuclear waste.
Steps for reducing energy consumption should be such that we get maximum energy from
least fuel. For this:
i.
Under the given situation technology utilized should be the best possible. For
example. Using smokeless chulhas should be preferred to traditional chulhas.
ii.
Energy should be extracted by most economic method under the given situation.
Where as energy extraction by solar cells may be useless in big towns due to cost
factor, it may be indispensable for artificial satellites.
iii.
Wastage of energy should be strictly avoided. Energy saved is equal to energy
produced.
iv.
Sources of energy should be such that it causes least damage to environment.
15.Our environment
VSAQ (1 marks)
1.
Would you eat animals or plants to get more calories of heat?
Ans. We should eat plants to get more calories of heat.
2.
What will happen if we kill all the organisms in one tropic level?
Ans.If we kill all the organisms in one tropic level, unbalances are created in the food
chain.
3.
Write an aquatic food chain?
Ans. Phytoplankton ton
zooplankton
fish
seal
4.
Why ozone layer is called radiation belt?
Ans. Because it checks the entry of high energy UV-radiations of sunlight in the earth’s
atmosphere.
5.
What is detritus?
Ans. Dead organic matter.
6.
Explain why the practice of serving tea in Kulhads (disposable cups made of clay)
on trains has been discontinued.
Ans. Because the use of a lot of clay for making millions of Kulhads daily lead to the loss
of fertile top soil in the fields.
7.
Write the full form of CFC. Give its one harmful effect.
Ans. The full form of CFC is Chloroflouro-carbons. Chloroflouro carbons are damaging
the ozone layer in the upper atmosphere.
SAQ (2 marks)
1. How is the ozone formed?
Ans. Ozone is formed high up in atmosphere by the action of ultraviolet radiation on
oxygen gas as follows.
Uv-radiation
O2 (from sun)
O2 + O
O
atom
Oxygen atom
Oxygen molecule.
+
O
atom
O3 (ozone molecule)
2. State any two practices which can help in the protection of our environment.
Ans. i. Disposal of waste after its separation as biodegradable and non-biodegradable
waste material
ii. Judicious use of unleaded petrol, alternate sources of energy. Engines of vehicles
should also be properly tuned and serviced so that vehicles run efficiently.
3. Give two ways in which biodegradable substance would affect the environment.
Ans. i. Stink- Within a day or so waste biodegradable substances begin to stink and
produce foul gases.
` ii. Pests and Pathogens- the decaying biodegradable substances become breeding
places of many pests. Because of being waste in origin they often contain pathogens.
4. Which of the following are biodegradable and which non-biodegradable?
Glass bottle, Paper, Ball point pen refill, DDT, Wheat, Cake, Wood, Polythene bag,
Cotton, Grass, Vegetable peels.
Ans. i. Biodegradable: Paper, Wheat, Cake, Wood, Jute bag, Cotton Cloth, Grass,
Vegetable peels.
ii. Non- biodegradable: Glass bottle, Ballpoint pen refill, DDT, Polythene bag.
5. What is ‘Ten percent low’?
Ans. Ten percent low is an enunciation given by Lindeman (1942) that states that only
10% of energy contained in a lower tropic level, the remaining 90% being lost in transfer
and respiration of the later.
SAQ (3 marks )
1. How is solar energy introduced into the ecosystem?
Ans. The green plants have a mechanism for trapping solar energy with the help of their
green pigment called chlorophyll. The green plants after trapping the solar energy,
convert it into chemical energy whish is stored as carbohydrates in the plants. Thus the
initial point where energy from the environment enters into the living components of
ecosystem (like plants and animals) is the process of preparation of food by green plants
through photosynthesis.
2. How can you help in reducing the problems of waste disposal?
Ans. 1. Recycling of wastes.
2. Reduction at source.
3. Better management.
4. Vermi-composting.
`
5. Use of eco friendly products such as disposable paper cups in place of plastic
cups,
Chapter 16
Management of Natural Resource
VASQ(1 marks)
1. Write utility of construction of dam and reservation.
Ans. Regular supply of water for irrigation, controlling floods and generating electricity.
2.
Define biodiversity.
Ans. It refers to totality of genes, species and ecosystem of a region, eg -Forest.
3. Why was Ganga Action plan launched?
Ans. To restore quality of water in the Ganga. It was very poor due to pollution.
4. What are the three R’s to save environment?
Ans. Reduce, Recycle and Reuse.
5.The presence of which organism indicates the pollution index of water body?
Ans. The presence of coli form group of bacteria indicates the pollution index of water body.
6. Name the river with which Sardar Sarovar Dam is associated.
Ans. The river with which Sardar Sarovar Dam is associated is Narmada.
7. Give one criticism about large dam.
Ans. Large dams consume large amount of public money without the generation of
proportionate benefits.
SAQ(2 marks)
1. Mention two ways in which water harvesting can be undertaken.
Ans. i. Capturing sum off water from roof-tops.
ii. Capturing sum off water from local catchments.
2. Why reuse better than recycling?
Ans. Reuse is better than recycling because the process of recycling uses some energy. In the
reuse strategy we simply use things again and again.
3. What would be advantages of exploring resources with short terms aims?
Ans. Exploring resources with short-term aims provide immediate advantage that meet
current basic human need.
4. How can you as an individual contribute or make a difference to management of (i) water
resources and (ii) Coal and petroleum?
Ans.(i) Running water will not be used for brushing teeth or taking bath. Water will be taken
in a mug and bucket for these purpose to prevent wastage.
(ii) Switch off unnecessary lights and fans etc. and use bicycle to cover short distances
instead of a scooter or car.
5. Write down any two consequences of deforestation.
Ans. i. Change in climate and global warming
ii. Soil erosion and floods.
6. Name any two endangered plant and animal species.
Ans. Endangered plant species- Pitcher Plant and Snow orchid.
Endangered animal species- Indian wild Ass and Great Indian Rhinoceros
SAQ ( 3marks)
1. Can you suggest some changes in yours school whish would make it environment friendly?
Ans. i. School busses should be run on CNG instead of diesel.
ii. Trees should be planted along the school boundary.
iii. The fallen leaves of trees should be collected and made into compost. This compost
can be used in school garden.
2. What are the causes of pollution of Ganga river?
Ans. 1. Dumping of garbage and untreated swage from all the towns and cities on the banks
of the ricer.
ii. Bathing by millions of people, washing clothes, animals and vehicles in the river
water.
iii. Immersion of ashes or even dead bodies in the performance of rituals.
iv. Releasing chemical effluents from industries directly into the river water.
3. Find out the traditional system of water-harvesting/ management.
Ans. Traditional system of water harvesting/ management.
i. Diversion of water flowing in streams into man made channels to cater to the demand
of the people
ii. Collection of water in ponds.
iii. Contraction of dams.
4. Why is dependence of man or nature greater than that of any other organism?
Ans. Man’s dependence on nature is greater than that of any other organism because he:
i.
Has developed curiosity for more comforts and security.
ii.
Consumes large amount of material and energy.
iii.
Has developed a new bond of socio-economic environment which consists
of things developed by man through his tools and techniques.
5.What is Chipko Andolan?
Ans. This movement was launched by people of Reni in Garhwal. It was spearheaded by
Sundar Lal Bahuguna. The Chipko Andolan (Hug the trees Movement) was the result of a
grass- root level effort to end the alienation of people from their forests. The movement
originated from an incident in a remote village called Reni in Garhwal during the early
1970’s The women of the village reached the forest and clasped the tree trunks to trees and
felling it. Thus thwarted the constructor had to withdraw.