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

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NCERT Solutions Download Class 7Chapter NameNCERT Solutions Download Class 7Chapter Name
NCERT Solutions For Class 7 Science Chapter 1: Nutrition In PlantsNutrition in PlantsNCERT Solutions for Class 7 Chapter 10 Respiration in OrganismsRespiration in Organisms
NCERT Solutions for Class 7 Chapter 2 Nutrition in AnimalsNutrition in AnimalsNCERT Solutions for Class 7 Chapter 11 Transportation in Animals and PlantsTransportation in Animals and Plants
NCERT Solutions for Class 7 Chapter 3 Fibre to FabricFibre to FabricNCERT Solutions for Class 7 Chapter 12 Transportation in Animals and PlantsReproduction in Plants
NCERT Solutions for Class 7 Chapter 4 HeatHeatNCERT Solutions for Class 7 Chapter 13 Motion and TimesMotion and Times
NCERT Solutions for Class 7 Chapter 5 Acids,Bases and SaltsAcids,Bases and SaltsNCERT Solutions for Class 7 Chapter 14 Electric Current and its EffectsElectric Current and its Effects
NCERT Solutions for Class 7 Chapter 6 Physical and Chemical ChangesPhysical and Chemical ChangesNCERT Solutions for Class 7 Chapter 15 LightLight
NCERT Solutions for Class 7 Chapter 7Weather,Climate and Adaptations of Animals to ClimateNCERT Solutions for Class 7 Chapter 16 Water;A precious resourceWater;A precious resource
NCERT Solutions for Class 7 Chapter 8Winds Storms and CyclonesNCERT Solutions for Class 7 Chapter 17 Forests;Our life lineForests;Our life line
NCERT Solutions for Class 7 Chapter 9SoilNCERT Solutions for Class 7 Chapter 18 Waste water storyWaste water story
NCERT Solutions for Class 7 Science Chapter 6 Physical and Chemical Changes

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 NotesCBSE Class 7 Science Study Notes
Nutrition in Plants Class 7 Notes Chapter 1Respiration in Organisms Class 7 Notes Chapter 10
Nutrition in Animals Class 7 Notes Chapter 2Transportation in Animals and Plants Class 7 Notes Chapter 11
Fibre to Fabric Class 7 Notes Chapter 3Reproduction in Plants Class 7 Notes Chapter 12
Heat Class 7 Notes Chapter 4Motion and Times Class 7 Notes Chapter 13
Acids,Bases and Salts Class 7 Notes Chapter 5Electric Current and its Effects Class 7 Notes Chapter 14
Physical and Chemical Changes Class 7 Notes Chapter 6Light Class 7 Notes Chapter 15
Weather,Climate and Adaptations of Animals to Climate Class 7 Notes Chapter 7Water;A precious resource Class 7 Notes Chapter 16
Winds Storms and Cyclones Class 7 Notes Chapter 8Forests;Our life line Class 7 Notes Chapter 17
Soil Class 7 Notes Chapter 9Waste water story Class 7 Notes Chapter 18

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