Summer Holiday Homework
Session 2013 – 2014
Name :
Class : VIII
Subject : Chemistry
General instructions:
1. The holiday h.w.should be neatly done in the notebook.
2. The worksheet should be pasted in the notebook.
3. Vasant
WhileKunj,
attempting
the- 110070
mcqs,write the correct option number alongwith the correct statement.Question
D-II,
New Delhi
Subject : ______________
need not be rewritten.Do not attempt the mcqs on the worksheet.
I
Answer the following questions after reading carefully the information given
below :
During the Middle Ages,there existed a kind of primitive science called alchemy.Its
objective was to discover a substance called the philosopher’s stone.This material was
thought to transform common metals such as lead into silver or gold.
Alchemists were predecessors of chemists.
One of the ancient ideas held by the alchemists was that matter was composed of four
“elements” --- earth,air,water,and fire which came from one common source.
Water was believed to be an element or distinct single substance. It was in 1781,that the
English chemist Henry Cavendish proved that water is a compound made of two elements
hydrogen and oxygen.He did this by showing that when hydrogen was burnt in oxygen
,water was formed.
Matter was thought to have a soul,which could be transferred from one element to
another.
Each element is represented by a chemical symbol.It uses the first letter and sometimes
the second letter of the English name or the Latin name of the element.For e.g.,the
symbol S is used for sulphur,the symbol for sodium is Na which is derived from the Latin
name natrium.The only exception to English and Latin symbols is the element tungsten
represented by W ,which is based on its German name,Wolfram.
Q1.
How did the modern branch of chemical sciences (chemistry )originate?
Q2. Who were alchemists?
Q3. Identify the scientist who proved that water is not an element but a compound.How
did he prove it?
Q4. Which element is represented by the symbol W?How is this chemical representation
different from the symbols of other elements?
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II
Complete the following table.
Element
Atomic
Number of
Name
number
protons
Symbol
aluminium
13
silicon
14
phosphorus
15
sulphur
16
chlorine
17
Argon
Ar
18
potassium
19
calcium
20
Number of
electrons
Mass number
Number of
neutrons
27
14
31
16
35
22
39
20
III.
Read ancient views on composition of matter and answer the questions that follow:
The great Indian sage Kannad(8thcentury B.C.) was the first to suggest that matter is
composed of very small particles called parmanus.
The Greek philosopher,Democritus (460- 370B.C.)and his followers were of the opinion
that all matter is made up of very small particles called atoms.The word atom comes from
the greek word atomio which means something that cannot be divided further.
Plato
Democritus
Plato(428-348 B.C.) , Aristotle(384-270B.C.) and some early Indian philosophers
classified matter in the form of five basic elements – earth,fire,sky,water,air.
Q 1: What is the basic idea conveyed by ancient philosophers regarding composition of
matter?
Q2: A sub-atomic particle is a particle that is smaller than the atom. A fundamental
particle is a particle that is present in every matter. Give example one each of a subatomic particle and a fundamental particle.
IV.
Elements such as helium(He),neon(Ne),argon(Ar) are least reactive.Their atoms
contain two(duplet) or eight electrons(octet) in their outermost shell.From this it can be
inferred that the presence of eight electrons in the outermost shell result in lack of
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reactivity.Therefore the atoms or ions having an octet of electrons in their outermost
shell are considered stable.
Electronic configuration of noble gases
S.no. Element
Atomic no.
Electronic
configuration
1.
Helium(He)
2
2
2.
Neon(Ne)
10
2,8
3.
Argon(Ar)
18
2,8,8
4.
Krypton(Kr)
36
2,8,18,8
5.
Xenon(Xe)
54
2,8,18,18,8
6.
Radon(Rn)
86
2,8,18,32,18,8
The number of electrons in the outermost shell of atoms of elements varies from 1 to
8.The atoms of elements which do not have an octet of electrons in their outermost shell
tend to do so either by transfer or by sharing of electrons with other atoms.During this
the atoms combine with one another to form molecules.Thus the tendency of atoms of
elements to attain an octet is the cause of their chemical reactivity and formation of a
chemical bond between two atoms.
A bond formed by transfer of electrons is known as an ionic bond or electrovalent bond .A
bond formed by sharing of electrons is known as a covalent bond.
When an atom loses electrons it becomes a positively charged species called cation.
When an atom gains electrons,it becomes a negatively charged species called an anion.
Therefore,we can also say that an ionic bond is formed between a cation and an
anion.Metal atoms can lose electrons to form a cation.Non-metal atoms can gain electrons
to form anions.Therefore,we can say that an ionic bond is formed between a metal atom
and a non-metal atom.A covalent bond is usually formed between two non-metal atoms.
Elements
Metals
Non-metals
Sodium
hydrogen
magnesium
carbon
calcium
oxygen
aluminium
nitrogen
iron
chlorine
copper
iodine
potassium
fluorine
Gold,silver
sulphur
Now,answer the following questions:
Q1.
Why does an atom of an element react with another atom to form a molecule?
Q2.
Give reason for the fact that noble gases are least reactive.
Q3.
State the meaning of the term octet configuration.
Q4.
Identify the type of bonds you would expect to find in the molecules of the
following substances:
Hydrogen gas ,Iodine , Magnesium chloride , Sodium oxide , Carbon dioxide
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QUESTIONS BASED ON PSA
Q1.
In each question below is given a statement followed by two courses of action
numbered I and II. You have to assume everything in the statement to be true and
on the basis of the information given in the statement, decide which of the
suggested courses of action logically follow(s) for pursuing.
1.
Statement: A large number of people in ward X of the city are diagnosed to
be suffering from a fatal malaria type.
Courses of Action:
I.
II.
The city municipal authority should take immediate steps to carry out
extensive fumigation in ward X.
The people in the area should be advised to take steps to avoid
mosquito bites.
A.
Only I follows
B.
Only II follows
C.
Either I or II follows
D.
Neither I nor II follows
E.
Both I and II follow
2. Statement: Severe drought is reported to have set in several parts of the
country.
Courses of Action:
I.
II.
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Government should immediately make arrangement for providing
financial assistance to those affected.
Food, water and fodder should immediately be sent to all these areas
to save the people and cattle.
A.
Only I follows
B.
Only II follows
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C.
Either I or II follows
D.
Neither I nor II follows
E.
Both I and II follow
Q2.
In each of the following questions you are given a combination of alphabets and/or
numbers followed by four alternatives (1), (2), (3) and (4). Choose the alternative
which is closely resembles the mirror image of the given combination.
1. Choose the alternative which is closely resembles the mirror image of the
given combination.
A.
1
B.
2
C.
3
D.
4
2. Choose the alternative which is closely resembles the mirror image of the
given combination.
A.
1
B.
2
C.
3
D.
4
Q3.
In each problem, out of the five figures marked (1), (2), (3), (4) and (5), four are
similar in a certain manner. However, one figure is not like the other four. Choose
the figure which is different from the rest.
1. Choose the figure which is different from the rest.
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(1)
(2)
(3)
(4)
(5)
A.
1
B.
2
C.
3
D.
4
E.
5
2. Choose the figure which is different from the rest.
(1)
6
(2)
(3)
(4)
(5)
A.
1
B.
2
C.
3
D.
4
E.
5
Q4.
Three gases found in earth’s atmosphere are carbon dioxide , nitrogen and oxygen.
What is their order of abundance from greatest to least?
A. Nitrogen , oxygen ,carbon dioxide
B. Nitrogen , carbon dioxide ,oxygen
C. Oxygen , nitrogen , carbon dioxide
D. Carbon dioxide , oxygen , nitrogen
Q5.
Dhruti has four unknown solutions and she wants to test whether they are acidic
or basic. She listed down four ways by which she can do this:
1. By tasting the solutions and finding out if they are sour or bitter.
2. By adding few drops of phenolphthalein to the solutions.
3. By touching the solutions and finding out if they are soapy or not.
4. By adding turmeric solution to the solutions.
Which of the above method/methods should Dhruti AVOID performing?
A. Only 1
B. Only 2
C. Both 1 and 3
D. All of them can be performed
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Q6.
The stomach normally secretes acid that is essential in the digestive process. This
acid helps in breaking down the food during digestion. When there is excess
production of acid in the stomach , it results in the condition known as acidity.
Antacid tablets like digene or gelusil are consumed by people suffering from
acidity. Which of the following CORRECTLY explains how antacids help relieve the
symptoms of acidity?
A. They act like sponges and absorb the acid from the stomach.
B. They are powerful acids which male the stomach acids weak.
C. They are bases which react with the stomach acids and lower the acidity in the
stomach.
D. They are neutral substances which react with the stomach acids and neutralize
them.
Q7.
Sumita found a container with a part of the label on the back. This is what she
could read on the label :
Use at bed time and after rising
in the morning.
FOR EXTERNAL USE ONLY
“ NOT FOR INJECTION”
Use within one month after
opening the container.
Q8.
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Which of the following is the label usually found on/
A. A box of tablets
B. A jar of face cream
C. A bottle of eye drops
D. A tube of toothpaste
An obsolete scientific theory is a scientific theory that ,though once widely
accepted, has since been discarded. For example , the Flat Earth theory states
that the earth’s shape is flat, like that of a paper. This is an obsolete scientific
theory because it has been proved that the earth’s shape is not flat but almost
spherical. Which of the following is another obsolete scientific theory?
A. Lamarckism : characteristics that an organism develops during its lifetime , like
the liking for music or books can be passed on to its offspring.
B. Theory of heat transfer : heat always flows from an object which is at a higher
temperature, to an object at a lower temperature.
C. Heliocentrism : according to this theory,the earth and other planets revolve
around the sun.
D. Germ theory of disease : most infectious diseases are caused by germs.
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Q9.
Compost is made by filling a pit with dry leaves and other vegetable wastes. This is
covered up with soil and kept damp. It is frequently mixed to speed up the process.
Which of the following processes occurring in nature is MOST similar to composting
and enhances the fertility of soil?
A. Breakdown of dead material in the forest floor.
B. Formation of petroleum reserves under the ground.
C. Incorporation of nitrogen compounds in soil by lightning.
D. Absorption of soil nutrients by the root hairs of trees.
Q10. Litmus paper or solution is used to test if substances are acidic or basic. The colour
Change produced under vatious conditions using litmus is shown below:
Substance
Acidic
Basic
Neutral
Blue litmus
Turns red
No change in colour
No change in colour
Red litmus
No change in colour
Turns blue
No change in colour
Anisha wanted to test a liquid X. She took a few drops of it and added a few drops
of blue litmus solution to it. There was no change in colour. Which of the following
can be DEFINITELY said about liquid X?
A. It is neutral.
B. It is not basic
C. It is not acidic.
D. It is either acidic or basic.
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