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Elements, Mixtures, & Compounds
1. Define elements, compounds, and mixtures?
Elements: A pure substance that can’t be further divided by physical or chemical
means.
Mixtures: Made up of two or more elements just physically combined.
Compounds: Made up of two or more elements chemically combined and can be
chemically separated.
2. What is the difference between mixtures and compounds?
Mixtures:
 Physically combined
 Not a fixed ratio of combining elements
 Constituent elements keep their properties
 Easily separated
 Eg: Salt & Water
Compounds:
 Chemically combined
 Combined in a fixed ratio
 Properties will be different of elements
 Can’t be easily separated
 Eg: CO2
3. What is the difference between an element and a compound?
Elements are pure substances while compounds are made up of two or more elements
chemically substances.
4. Discuss the methods of formation of compounds with an example.
Combination: When elements and compounds burn and combine with oxygen.
Decomposition: When complex compounds are heated to break them down into
simpler compounds.
5. Discuss some common properties of mixtures.
It has the properties of its constituent substances. It can be easily separated by
physical means and they are not mixed in any fixed proportion.
6. What are different types of mixtures? Explain with examples.
Solid-Solid Mixtures:
When a solid is mixed with a solid.
Zinc+Aluminum= Alloy
Liquid-Liquid Mixtures:
When two different liquids combine and form a new mixture.
Ethanol+Water=Drinks
Solid-Liquid Mixtures
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When a solid is combined with a liquid.
Water + Tang
Liquid-Gas Mixtures:
When a gas is mixed with a liquid.
Flavoured Liquid + Carbon Dioxide = Drinks
Gas-Gas Mixtures
When two different gases combines.
Air= Oxygen + Carbon Dioxide etc
7. What is the link between solubility and temperature of a compound?
If the temperature increases the solubility increases and if the temperature decreases
the solubility decreases.
8. Which element is the most abundant in air?
Nitrogen, 78%.
9. Which two elements are the most abundant in the Earth’s crust?
Nitrogen and Oxygen.
10. Which element is combined with oxygen to form sand?
Oxygen is combined with silicon.
11. What is the use of oxygen for humans and plants?
12. What two elements make water?
Two atoms of hydrogen and one atom of oxygen.
13. What is the chemical formula for water?
H2O
14. What do common properties of some elements allow them to be classified
into?
Metals and Non-metals.
15. How are metals different from non-metals? Give two examples of each.
Metals are shiny and malleable while non-metals are dull and brittle.
16. What is the melting point of mercury?
38.9oC.
17. On what basis are elements arranged in the periodic table?
According to their increasing atomic number.
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18. What have the scientists organized to study the properties of elements
systematically?
19. Who was the first person to compile a true table of elements, and how many
elements did he arrange on the periodic table?
Dmitri Mendeleev.
20. What is a chemical symbol? Give examples.
The names of chemical represented by a symbol.
21. What are the categories of elements in the periodic table? Give examples.
On the left side are metals and on the right are non-metals and in between are
metalloids.
22. Why are water and carbon dioxide not found in the Periodic Table?
Because they are not elements they are compounds.
23. What are metalloids? Give examples
Which contain properties of both non metals and metals.
24. Are the properties of a compound same of its constituent elements?
No, they are usually different.
25. What are some characteristics of a compound?
Constituents are in fixed proportions.
Methods are: Combination and Decomposition.
Compounds are different from its constituent elements.
26. When does decomposition of a compound occurs?
When complex compounds are heated to break them into simpler compounds.
27. What is the air mixture of?
Elements. For eg: Carbon Dioxide, Oxygen, and Nitrogen.
28. What substances make a mixture?
Two or more different substances.
29. What is an alloy? Give examples.
30. Fill in the blanks.
1. Nitrogen makes 78% of the air whereas oxygen makes up 21%.
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2. Water can be separated into its constituent elements hydrogen and oxygen
by passing an electric current through it. Therefore water is not an element.
3.
is one
that is liquid at room temperature.
4. The
table organizes elements broadly into
5. The sun is a giant ball of
and
and
gases.
6. the names of elements ate represented by
7. Elements that are arranged in the same horizontal row belong to the same
8.
is a highly reactive solid at room temperature
9. Compound is formed by a chemical reaction.
10. One common example of combination is
11. Milk is a mixture of
such as
and
12. When a mixture is formed, no
occurs.
13. Element is the basic building block of matter.
1Q.
Complete the following table.
Elements
Properties
Uses
Aluminum
Shiny, strong, light weight
Making utensils
Copper
Make pipes, used in homes
Reddish Brown, Strong,
Malleable
Iron
Good conductor, ductile, strong
Make cutlery
Iodine
Black, poisonous
Medicines
Sulphur
Yellow, Soluble
Rubber tires
Carbon (Diamond)
Hard, can be polished
Diamond drills can cut
through hard metals
Carbon (Graphite)
2Q.
Black, Light Weight
Complete the following table.
Mixtures
Iron & Gold
Sulphur & Iron
Carbon & Salt
Zinc Sulphide
3Q.
Make rackets
Complete the following table.
Separation Method
5
4Q.
Elements
Symbol
Atomic Number
Hydrogen
H
1
Boron
B
5
Lithium
L
3
Neon
Ne
10
Helium
He
2
Argon
Ag
18
Nitrogen
N
7
Magnesium
Mg
12
Fluorine
F
9
Potassium
K
19
Carbon
C
6
Silicon
Si
14
Calcium
Ca
20
Chlorine
Cl
17
Aluminum
Al
13
Sulphur
S
16
Beryllium
Be
4
Phosphorus
P
15
Oxygen
O
8
Sodium
Na
11
Complete the following table.
Compounds
Glass
Water
Table Salt
Sugar
Chalk
5Q.
Complete the following table.
Elements Contained
6
6Q.
Compounds
Chemical Formulas
Carbon Dioxide
CO2
Water
H2O
Sodium Chloride
Na Cl
Calcium Carbonate
CaCO3
Copper Sulphate
Cu SO4
Sulphur Dioxide
SO2
Sugar
C6H12O6
Hydrogen Chloride
HCL
Sodium Hydroxide
Na OH
Hydrogen Sulphate
H2SO4
Hydrogen Nitrate
HNO3
Complete the following table.
Element
Element
(Metal)
(Non-metal)
Properties
Atomic
Number
Colorless gas; essential for life; does not
burn but supports combustion
1
Aluminum
Chlorine
Yellow powdery solid; Poisonous; soluble
in organic solvent (e.g., alcohol) but not in
water
12
Nitrogen