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:
C.C
P.C
C.C
P.C
P.C
C.C
FALSE
FALSE
TRUE
FALSE
TRUE
CaCO3.
NaHCO3.
GALVANIZATION, ELECTROPLATING.
PHYSICAL.
CHEMICAL.
NON.
EVOLUTION OF HYDROGEN GAS. IT IS A CHEMICAL CHANGE BECAUSE OF THE FORMATION OF NEW SUBSTANCE BAKING POWDER.
Chemical Changes : The wax near flame burns and gives new substances like carbon dioxide, carbon soot, water vapour, heat and light. LPG is another example of a familiar process in which both the chemical and physical changes take place.
Setting of curd is a chemical change because we cannot get the original substance (milk) back. The new substance, i.e. curd is different from the milk in taste, smell and chemical properties.
Burning of wood is a chemical change while cutting of wood is a physical change because during burning, new substances are formed. After burning, we cannot get original substance, (i.e. wood) back.
Crystallization is the process by which we can obtain crystals of copper sulphate. In this process, a few drops of dilute sulphuric acid is added to water. The water is then boiled & as it starts boiling, copper sulphate powder is added with stirring. ... After some time the crystals of copper sulphate separate out.
Painting prevents direct interaction of iron, air and moisture. Hence, painting of an iron gate prevents it from rusting.
The atmosphere contains moisture in the form of humid air. Thus, in coastal areas, both moisture and air are present abundantly. Hence, in coastal areas, rusting takes place at a faster pace. However, in deserts, air is usually dry with very small amounts of moisture.
Tearing a paper is a physical change because when the paper is torn only the appearance of paper is changed. 2. Physical changes are reversible.
Chemical reaction, a process in which one or more substances, the reactants, are converted to one or more different substances, the products.
Galvanisation or galvanization (or galvanizing as it is most commonly called) is the process of applying a protective zinc coating to iron or steel, to prevent rusting. The most common method is hot dip galvanizing, in which steel sections are submerged in a bath of molten zinc.
Galvanisation or galvanization (or galvanizing as it is most commonly called) is the process of applying a protective zinc coating to iron or steel, to prevent rusting. The most common method is hot dip galvanizing, in which steel sections are submerged in a bath of molten zinc.
Crystallization is a common and useful laboratory technique. It can be used to purify substances, and can be combined with advanced imaging techniques to understand the nature of the substances crystallized. In laboratory crystallization, a substance can be dissolved into an appropriate solvent.
Physical changes are mostly reversible because they involve changes in the physical properties of a substance such as state, shape, size, colour etc. and no new substances are formed in a physical change.
Ozone molecules destroy and oxygen molecules form. So new chemical substances are formed by consuming the starting material hence it is a chemical change. It is a chemical change as new substance is formed during the process.
Process—B is a chemical change.
(c) Both processes A and B are chemical changes.
loss of metal.
(b) irreversible.
(c) two or more metals are mixed in a fixed ratio.
d. chemical change.
e.physical change.
b. reactants and products.
c. acid + base → salt +water.
a. rusting.
Mg(OH)2+ H2.
CaCO3+H2O.