NCERT solution class 7 science ch 6 -physical and chemical change.

Get the NCERT solution for Class VI Science Chapter 6. These NCERT solutions for science topic 7 include detailed answers to all questions in Chapter 6 - Physical and Chemical Changes. .

Class 7 book

questions 1 to 5.

Q 1.Classify the changes involved in the following processe as physical or chemical changes:-
Answer:(a)photosynthesis→chemical change
(b)dissolving sugar in water→physical change
(c)Burning of coal→Chemical change
(d)melting of wax→physical change
(e)beating aluminium to make aluminium foil→physical change
(f)Digestion of food→chemical change.

Q 2.state whether true or false..
Only anshwer:(a) F
(b) F
(c) T
(d) F
(e) T

Q 3.fill in the blanks...
(a)calcium carbonate (CaCO3) .
(b)sodium hydrogen carbonate.
(c)galvanization and painting.

Q 4. when    baking.  soda. is mixedwith lemon juice,bubbles are formed with the evolution of a gas.what type of change is it?
Answer:When.baking.soda (sodium hydrogen carbonate) is mixed with lemon juice (citric acid),bubbles are formed. Bubbles are formed due to the development of carbon dioxide gas.
This is a chemical change.
In this transformation, the citric acid contained in lemon juice reacts with sodium hydrogen carbonate, which results in the development of carbon dioxide gas.
Lemon juice+baking soda→carbon dioxide+other substances
Citric acid sodium
Hydrogen carbonate

Q 5.When a candle burn,both physical and chemical changes take place. Identify these changes. 
Giveanother example of a familiar process in which both the chemical and physical changes take place.
Answer:When a candle burn,both physical and chemical changes occur.
Body change→melting of wax
Chemical change→wax is burning
Meal meal are another example where both physical and chemical change occur together.
Body changes→Breaking large food particles in small particles
Chemical change→digestion of food.

 questions 6 to 12.

Q 6.How. wouldyou show that setting of curd is a chemical change .?
Answer:Once the curd is formed, it can not be recovered with milk again. Apart from this, both milk and curd have different properties. Since these are the properties of chemical change, the establishment of curd is a chemical change.

Q 7.Explainwhy burning of wood and cutting it into small piece are considered as two different types of changes.
Answer:When we burn wood, then a new substance, coal is formed. Therefore, this is a chemical change. However, when we cut wood, the size and shape of the wood changes. No new material has been made. Therefore, it is a physical change.

Q 8.Describe. how crystals of copper sulphate are prepared.
Answer:The crystals of copper sulphate are prepared by the method of crystallization. Thus the process is.A.cup of water is taken in a beaker. Some drops of diluted sulfuric acid are included in it. The water is heated and when it starts boiling, then copper sulphate powder is added with stirring. The solution should be added until the solution is saturated. Then it is filtered into a China dish and is allowed to cool. The solution should be kept indisputable. Gradually, crystals of copper sulfate are different

Q 9.Explainhow painting of an iron gate prevents it from rusting.
Answer:Jung is assisted by both humidity (water) and air (oxygen). By portraying the iron door, we stop the air and moisture in your atmosphere. Therefore, the wild is being stopped.

Q 10.Explainwhy rusting of iron objects is faster in coastal areas than in deserts.
Answer:To be wild, both air and moisture are required. In coastal areas, the amount of moisture present in the air is higher in the desert. In the desert areas, the amount of moisture content in the air is also low. Therefore, compared to the desert, the wild objects of the iron objects in the coastal areas are increasingly fast.

Q 11.t he gas we use........
Answer:(ii)Process− B is a chemical change

Q 12.Anaerobic bacteria book..
Answer:(iii)both proceses A and B are chemical changes.

The end....


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