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WORKSHEET
Year: 2015-16
Subject: Science
Class: VII (A & B)
Topic: Physical and Chemical Changes
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Choose the correct option from the following questions:
Melting of ice is a
a. Chemical change
b. Physical change
Which of these is the smallest particle?
a. An atom
b. A molecule
Formation of a compound is
a. Physical change
b. Temporary change
Sea water is a
a. Element
b. Compound
Which of the following is a reversible change?
a. Melting of ice
b. Burning of match stick
Which of the following is an example of chemical change?
a. Melting of wax
b. Burning of candle wick
In a chemical change
a. Molecule of substance do not change
b. Molecule of substance change
Which of the following is an example of physical change?
a. A bud turning into a flower
b. Rusting of iron
Physical changes are
a. Irreversible
b. Periodic
Chemical changes are characterised by
a. Formation of new substance
b. Release of energy
Symbol that represent sodium is
a. S
b. K
Crystallization is a process of obtaining
a. solids only
b. pure liquids only
Rusting of iron can be prevented by
a. Galvanising
b. Painting
c. Periodic change
d. Both physical and chemical change
c. A speck of dust
d. A water drop
c. Chemical change
d. Reversible change
c. Mixture
d. Molecule
c. Changing of milk into curd
d. Germination of seed
c. Heating of iron rod
d. Woolen yarn to knitted sweater
c. Substance remain the same
d. Change is reversible
c. Ripening of a tomato
d. Boiling of water
c. Reversible
d. All of these
c. Absorption of energy
d. Reversible
c. Na
d. Fe
c. pure gas only
d. all of these
c. Alloying
d. All of these
14. When an iron nail is dipped in the blue copper sulphate solution
i.
Colour of the solution changes to green
ii.
Brown deposit is observed on the iron nail
iii.
Brown deposits is observed at the bottom of the beaker
iv.
Which of the above statements are correct?
a. [i] & [ii] are correct
c. [ii] & [iv] are correct
b. [i] & [iii] are correct
d. [i] &[iv] are correct
15. Dissolution of sugar is a/an
a. Irreversible physical changes
c. reversible chemical changes
b. Irreversible chemical changes
d. reversible physical changes
16. A chemical change among the following occurs when
a. Salt is mixed with water
c. A paper boat is made by paper cutting
b. Wax is melted
d. A wax candle is burnt
17. Which of the following is not a chemical change?
a. Burning of log of wood
c. Curdling of milk
b. Chopping of trees
d. Heating of milk
18. On addition of baking soda to vinegar, we come to know that a chemical reaction has occurred as
a. Hydrogen gas is evolved
c. There is evolution of heat and light
b. Carbon dioxide gas is evolved
d. There is a change in color
NSO/HOTS QUESTIONS
1. Rohant observed formation of the green substance on a copper statue in his home. This formation is due to:
a. chemical change
c. periodic change
b. physical change
d. both (B) and (C)
2. Karan cuts a piece of wire and then bends to form pattern. Identify the change undergone by the wire.
a. Irreversible physical change
c. Chemical change
b. Reversible physical change
d. Initially chemical change later physical change
3. Look at the figure of whipping an egg white:
What kind of change is undergone by egg white?
a. Reversible chemical change
c. Physical change
b. Irreversible chemical change
d. Both physical as well as chemical change
4. Identify the following as a chemical (C) or physical property (P):
1.
2.
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7.
blue color
density
flammability (burns)
solubility (dissolves)
reacts with acid
supports combustion
sour taste
P
P
C
P
C
C
P
8. melting point
9. reacts with water
10. Hardness
11. boiling point
12. Luster
13. Odour
14. reacts with air
P
C
P
P
P
C
C
5. Read each scenario. Decide whether a physical or chemical change has occurred and give evidence for your
decision. The first one has been done for you to use as an example.
Scenario
Physical or
Chemical
Change?
Evidence…
No change in substances.
1.
Umm! A student removes a loaf of bread hot
from the oven. The student cuts a slice off
the loaf and spreads butter on it.
2.
Your friend decides to toast a piece of bread,
but leaves it in the toaster too long. The
bread is black and the kitchen if full of smoke.
Chemical
Toast has been burnt. New substance
formed, smoke is formed, change is
irreversible
3.
Food color is dropped into water to give it
color
Physical
Only change in colour,no new
substance is formed
4.
You blow dry your wet hair.
Physical
No change in substance, water
changes to water vapur[change of
state has taken place.
5.
In baking biscuits and other quick breads, the
baking powder reacts to release carbon
dioxide bubbles. The carbon dioxide bubbles
cause the dough to rise.
Chemical
New substance CO2 is formed,
6.
In a fireworks show, the fireworks explode
giving off heat and light.
Chemical
Heat & light is produced
Physical
No unexpected color change,
temperature change or gas given off.