NCERT Book Solutions for Class 7
Chapter Number 6: Physical and Chemical Changes
NCERT is a must-read book for school students. All the private publications book also follow the pattern of NCERT. So, completing NCERT questions becomes more important. We have shared NCERT Book solutions for class 8, 9, 10 earlier. Today we are here to share class 7 NCERT Solutions of the chapter Chemical and Physical Changes. It is an important chapter of Class 7th and each year some tricky questions are also asked in the final Class 7 exam. So, lets’ check out the NCERT Solutions Class 7 of Physical and Chemical Changes chapter.
NCERT Book Solutions Class 7: Chapter 6
NCERT Solutions Class 7: Question 1 to 5
Q1. Classify the changes involved in the following processes as physical or chemical
Photosynthesis
1. Dissolving of sugar in water
2. Burning of coal
3. Melting of wax
4. Beating Aluminium to make Aluminium foil
5. Digestion
Ans. Chemical change physical change or chemical change physical change or physical change or chemical change
Q.2. (a) cutting a log of wood into pieces is a chemical change (True/False)
(b) formation of manure from leaves is a physical change( True/False)
(c) iron pipes coated with zinc do not get rusted easily (True/False)
(d) Iron and rust are the same substances (True/False)
(e) condensation of steam is not a chemical change (True false)
Q.3. Fill in the blanks in the following statements
(a) When carbon dioxide is passed through lime water turns milky due to the formation of
(b) The chemical name of baking soda is…………………..
(c) Two methods by which rusting of iron and can be prevented are…. and…….
(d) Changes in which only ……. properties of a substance change are called physical changes.
(e) Changes in which new substances are formed are called ………..changes
Ans (a) calcium carbonate
(b)Sodium hydrogen carbonate
(c) Painting, greasing galvanization
(d) Physical
(e) Chemical
Q.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.
It is a chemical change. The reaction between the baking soda and lemon juice can be shown as below.
Q.5. When a candle burns both physical and chemical changes take place to identify these changes give another example of a familiar process and his both chemical and physical changes take place.
Ans. The burning of a candle is an example of both the physical and chemical change both the processes take place in this.
(i) physical change: melting of wax, the formation of vapours of the melted wax
Examples in which both physical and chemical changes occur at the same time are eating a chocolate, burning of wood.
Chemical change when vapours of wax are burned they release carbon dioxide heat and light energy
NCERT Solutions Class 7: Question 6 to 7
Q.6. How can you show that the formation of a curd is a chemical change
Formation of curd can be considered as a chemical change because the original substance of the product from which it was formed cannot be reverted back. You cannot obtain milk again from the curd.
Q.7. Explain why the burning of wood and cutting it into small pieces are considered as two different types of changes
The burning of wood will be considered as a chemical change because it give rise to the formation of new products and that’s why a chemical change occurs
Cutting of wood into smaller pieces will be considered as a physical change because it is not giving birth to a new product only the size of the product is reduced
Q. 8. Describe how the crystals of copper sulphate are prepared
Take 300 ml of water in a beaker and then add dilute sulphuric acid to the beaker. Start stirring the water. Add copper sulphate powder when the water starts boiling. You have to add copper sulphate powder till the limit has been read and no more copper sulphate powder can be dissolved in the beaker. Keep mixing the solution. After sometime filter the solution and allow it too cool for sometime. After sometime you can easily notice the crystals of copper sulphate formed.
Q.9. How the painting of an iron gate prevent it from rusting?
Painting of an iron gate will prevent its contact from the moisture and Oxygen gas which of the supporter of rusting. Painting at the layer of the rest can be easily prevented.
Q.10. Explain why the rusting of iron objects is faster in coastal areas than in deserts
The coastal areas have a very high amount of moisture present in the atmosphere as compared to the deserts. Rusting needs moisture that’s why rusting takes place faster in the coastal areas
Q.11. The gas used in the kitchen is called liquefied petroleum gas in the cylinder. It exist as a liquid when it comes out from the cylinder becomes a gas (change A), then it burns (change B) the following statement 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
Ans. (ii) Process B is a chemical change.
Q.12. Anaerobic bacteria digest animal waste and produce biogas (changeA). The biogas is then burnt as fuel change b. The following statement pertaining 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
Ans.(iii) Both processes A and B are chemical changes
So, these were NCERT Solutions for Class 7, chapter number 6 Chemical and Physical Changes. You can read the complete answers of the NCERT Book Questions for Class 7. Don’t forget to share this article with your school friends
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