NCERT Solutions for Class 7 Science Chapter 6 Physical and Chemical Changes
Learn from School Connect Online in this chapter we will learn about Physical and Chemical Changes as t here are several changes we come across daily e.g dissolving sugar in water, or flattening a metal rod by beating it. These involve changes in the form of the substance.NCERT Solutions for Class 7 Science Chapter 6 Physical and Chemical Changes
Download PDF of NCERT Solutions for Class 7 Science
NCERT Solutions Download Class 7 | Chapter Name | NCERT Solutions Download Class 7 | Chapter Name |
NCERT Solutions For Class 7 Science Chapter 1: Nutrition In Plants | Nutrition in Plants | NCERT Solutions for Class 7 Chapter 10 Respiration in Organisms | Respiration in Organisms |
NCERT Solutions for Class 7 Chapter 2 Nutrition in Animals | Nutrition in Animals | NCERT Solutions for Class 7 Chapter 11 Transportation in Animals and Plants | Transportation in Animals and Plants |
NCERT Solutions for Class 7 Chapter 3 Fibre to Fabric | Fibre to Fabric | NCERT Solutions for Class 7 Chapter 12 Transportation in Animals and Plants | Reproduction in Plants |
NCERT Solutions for Class 7 Chapter 4 Heat | Heat | NCERT Solutions for Class 7 Chapter 13 Motion and Times | Motion and Times |
NCERT Solutions for Class 7 Chapter 5 Acids,Bases and Salts | Acids,Bases and Salts | NCERT Solutions for Class 7 Chapter 14 Electric Current and its Effects | Electric Current and its Effects |
NCERT Solutions for Class 7 Chapter 6 Physical and Chemical Changes | Physical and Chemical Changes | NCERT Solutions for Class 7 Chapter 15 Light | Light |
NCERT Solutions for Class 7 Chapter 7 | Weather,Climate and Adaptations of Animals to Climate | NCERT Solutions for Class 7 Chapter 16 Water;A precious resource | Water;A precious resource |
NCERT Solutions for Class 7 Chapter 8 | Winds Storms and Cyclones | NCERT Solutions for Class 7 Chapter 17 Forests;Our life line | Forests;Our life line |
NCERT Solutions for Class 7 Chapter 9 | Soil | NCERT Solutions for Class 7 Chapter 18 Waste water story | Waste water story |
1. Classify the changes involved in the following processes as physical or chemical changes:
(a) Photosynthesis
Sol : Chemical Change
(b) Dissolving sugar in water
Sol : Physical Change
(c) Burning of coal
Sol : Chemical Change
(d) Melting of wax
Sol : Physical Change
(e) Beating aluminium to make aluminium foil
Sol : Physical Change
(f) Digestion of food
Sol : Chemical Change
2. State whether the following statements are true or false. In case a statement is false, write the corrected statement in your notebook.
(a) Cutting a log of wood into pieces is a chemical change. (True/False)
Sol : False
(b) Formation of manure from leaves is a physical change. (True/False)
Sol : False
(c) Iron pipes coated with zinc do not get rusted easily. (True/False)
Sol : True
(d) Iron and rust are the same substances. (True/False)
Sol : False
(e) Condensation of steam is not a chemical change. (True/False)
Sol : True
3.Fill in the blanks in the following statements:
(a) When carbon dioxide is passed through lime water, it turns milky due to the formation of _________.
Sol : When carbon dioxide is passed through lime water, it turns milky due to the formation of Calcium carbonate.
(b) The chemical name of baking soda is _________.
Sol : The chemical name of baking soda is Sodium hydrogen carbonate.
(c) Two methods by which rusting of iron can be prevented are _________ and _________.
Sol : Two methods by which rusting of iron can be prevented are painting and galvanization.
(d) Changes in which only _________ properties of a substance change are called physical changes.
Sol : Changes in which only physical properties of a substance change are called physical changes.
(e) Changes in which new substances are formed are called _________ changes.
Sol : Changes in which new substances are formed are called chemical changes.
4. When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas. What type of change is it? Explain.
Solution:
When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a carbon dioxide gas. This is a chemical change.
Lemon juice + Baking soda → Carbon dioxide + other substances
5. 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.
Solution:
Candle Burning
Physical change is melting of wax:
The chemical change is the burning of gas with the evolution of CO2
Digestion of Food
Physical change is the breakdown of larger food molecules to simpler ones
The chemical change is the digestion of food by the action of HCl and enzymes.
6. How would you show that setting of curd is a chemical change?
Solution:
The setting of curd is a chemical change because curd cannot be turned back to milk. The properties of milk and curd are different.
7. Explain why burning of wood and cutting it into small pieces are considered as two different types of changes.
Solution:
Cutting of wood is a physical change as it does not change the nature of the wood. On the other hand, burning of wood is a chemical change as wood is converted to charcoal with the liberation of CO2.
8. Describe how crystals of copper sulphate are prepared.
Solution:
Crystals of copper sulphate are prepared using the crystallization method, which is described as follows
- Take a cupful of water in a beaker.
- Add a few drops of dilute sulphuric acid to this.
- Heat the water and when it starts boiling, add copper sulphate powder while still stirring.
- Add the copper sulphate powder till the solution becomes saturated. Filter into a china dish and allow it to cool.
- The solution should be kept undisturbed. Slowly, the crystals of copper sulphate separate out.
9. Explain how painting of an iron gate prevents it from rusting
Solution:
Rusting of iron requires contact with water (moisture) and oxygen. By painting an iron gate, we prevent the contact between iron, Oxygen and water (moisture), this helps in preventing rusting of iron.
10. Explain why rusting of iron objects is faster in coastal areas than in deserts.
Solution:
Rusting of iron requires contact with water (moisture) and oxygen. In coastal areas, humidity is more in comparison to that in deserts; hence, rusting of iron objects is faster in coastal areas than in deserts.
11. 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.
(i) Process – A is a chemical change.
(ii) Process – B is a chemical change.
(iii) Both processes A and B are chemical changes.
(iv) None of these processes is a chemical change
Solution:
The answer is (ii) Process – B is a chemical change.
12. 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.
(i) Process – A is a chemical change.
(ii) Process – B is a chemical change
(iii) Both processes A and B are chemical changes.
(iv) None of these processes is a chemical change
Solution:
Answer is (iii) Both processes A and B are chemical changes.
CBSE Notes for Class 7 Science Free Download for All Chapters
CBSE Class 7 Science Study Notes | CBSE Class 7 Science Study Notes |
Nutrition in Plants Class 7 Notes Chapter 1 | Respiration in Organisms Class 7 Notes Chapter 10 |
Nutrition in Animals Class 7 Notes Chapter 2 | Transportation in Animals and Plants Class 7 Notes Chapter 11 |
Fibre to Fabric Class 7 Notes Chapter 3 | Reproduction in Plants Class 7 Notes Chapter 12 |
Heat Class 7 Notes Chapter 4 | Motion and Times Class 7 Notes Chapter 13 |
Acids,Bases and Salts Class 7 Notes Chapter 5 | Electric Current and its Effects Class 7 Notes Chapter 14 |
Physical and Chemical Changes Class 7 Notes Chapter 6 | Light Class 7 Notes Chapter 15 |
Weather,Climate and Adaptations of Animals to Climate Class 7 Notes Chapter 7 | Water;A precious resource Class 7 Notes Chapter 16 |
Winds Storms and Cyclones Class 7 Notes Chapter 8 | Forests;Our life line Class 7 Notes Chapter 17 |
Soil Class 7 Notes Chapter 9 | Waste water story Class 7 Notes Chapter 18 |
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