Physical and Chemical Changes Worksheets
A. Classify the changes involved in the following processes as physical or chemical changes:
1. Photosynthesis ………………..
2. Dissolving sugar in water …………………..
3. Burning of coal ……………..
4. Melting of wax ………………
5. Beating aluminium to make aluminium foil …………………..
6. Digestion of food …………………
B. State ‘True’ or ‘False’:
1. Cutting a log of wood into pieces is a chemical change …………………
2. Formation of manure from leaves is a physical change …………………
3. Iron pipes coated with zinc do not get rusted easily ………………….
4. Iron and rust are the same substances. ………………
5. Condensation of steam is not a chemical change. ……………….
C. Fill in the blanks:
1. When carbon dioxide is passed through lime water, it turns milky due to the formation of ………….. .
2. The chemical name of baking soda is ………………….. .
3. Two methods by which rusting of iron can be prevented are ………………. and ……………….. .
4. Changes in which only ……………….. properties of a substance change are called physical changes.
5. Changes in which new substances are formed are called ………………… changes.
6. Formation of crystals of sugar from a sugary syrup is a ……………….. chemical change.
D. Answer the following questions in short:
1. When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it? Explain.
2. When a candle burns, both physical and chemical changes take place. Identify these changes. Give another example of a familiar process in which both the chemical and physical changes take place.
3. How would you show that setting of curd is a chemical change?
4. Explain why burning of wood and cutting it into small pieces are considered as two different types of changes.
5. Describe how crystals of copper sulphate are prepared.
6. Explain how painting of an iron gate prevents it from rusting.
7. Explain why rusting of iron objects is faster in coastal areas than in deserts.
8. What kind of change is shown by tearing of paper?
9. Define chemical reaction.
10. What is the purpose of galvanising?
11. What is the use of crystallization process?
12. Why are physical changes generally reversible?
13. Can we call the breaking down of ozone a chemical change?
E. Tick (✓) the correct option:
1. The gas we use in the kitchen is called liquified petroleum gas (LPG). In the cylinder it exist as a liquid. When it comes out from the cylinder it becomes a gas (Change—A) then it burns (Change—B). The following statements pertain to these changes. Choose the correct one:
(a) Process—A is a chemical change.
(b) Process—B is a chemical change.
(c) Both processes A and B are chemical changes.
(d) None of these processes is a chemical change.
2. Anaerobic bacteria digest animal waste and produce biogas (Change—A). The biogas is then burnt as fuel (Change—B). The following statements pertain to these changes. Choose the correct one:
(a) Process—A is a chemical change.
(b) Process—B is a chemical change.
(c) Both processes A and B are chemical changes.
(d) None of these processes is a chemical change.
3. Rusting results in:
(a) gain of iron
(b) no loss of metal
(c) loss of metal
(d) none of these
4. Chemical changes are:
(a) reversible
(b) irreversible
(c) changes involving formation of one or more new substances
(d) both (b) and (c)
5. In making of alloys:
(a) more than two metals are mixed
(b) only two metals are mixed
(c) two or more metals are mixed in a fixed ratio
(d) none of the above
F. Match the following:
‘A’ ‘B’
1. Formation of curd from milk a. rusting
2. Melting of glaciers b. reactants and products
3. Chemical reactions c. acid + base → salt + water
4. Neutralization d. chemical change
5. Decaying of layers of metal e. physical change
G. Complete the following reactidns:
1. MgO (Magnesium oxide) + H2O(Water) →
2. CO2 (Carbon dioxide) + [Ca(OH)2] (Lime water) →
Answers
Answer:
A)1) chemical
2)physical
3)I don't know this one
4)both physical and chemical
5) physical maybe
6) chemical
B 1)false
2)false
3)true
4)false
5)true
C1)Carbon dioxide
2)sodium hydrogen carbonate
3)galvanisation and greesing
4)physical
5)chemical
D 1) It is a chemical change as it is not reversible as well as a new substance is formed in it .. i.e. , carbon dioxide...and heat energy is released.
2)This is both physical and chemical change because when the candle burns..it produces a new substance that is the carbon dioxide but the wax remains the same...and even after sometimes it again changes into solid state also. Another familiar example is boiling of egg..the boiling of egg is physical as well as chemical change..as the texture of egg is changed but the egg remains the same..and no new substance is formed..so it is physical and chemical both changes.
3)It is a chemical change as the milk is changed into curd..so a new substance is formed..So..it is a chemical change.
4)It is considered as two different types of changes because in burning of wood a new substance is formed that is carbon dioxide but in cutting of wood ..no new substance is formed..so cutting of wood is physical change and burning of wood is a chemical change(and they also satisfy the other characteristics of their changes)..therefore, they are different.
Explanation:
hope it helps
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Answer:
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