Question

3.Fill in the blanks in the following statements:

A) When carbon dioxide is passed through lime.Water it turns milky due to the foundation of ______
B) The chemical name of baking soda is ____
C) Two methods by which rusting of iron 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.
4. When baking soda is mixed with lemon juice,bubbles are formed with the evolution of a gas.What type of change it is it?Explain.
5. When a candle burns,both physical and chemical changes.Take place.Identify this change.Give another example of a familiar process in which both the chemical and physical change take place.
6. How could you show the setting of curd is a chemical change?
7. Example why burning of wood and cutting it into small pieces are considered as two different types of changes.
8. Describe how crystals of copper sulphate are prepared.
9. Example how painting of an iron gate prevents it from rusting.
10. Example why rusting of iron object is faster in coastal area then in deserts.
11. The gas we use in the kitchen is called liquified petroleum gas (LPG). In the cylinder it is as a liquid.When it comes out from the cylinder it becomes a gas (Change - A) then it burns (Change B). The following statement pertain to these changes.Choose the correct one.
1) Process - A is a chemical change.
2) Process - B is a chemical change.
3) Both process A and B are chemical changes.
4) None of these process 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 pretian to these changes.Choose the correct one.
1) Process - A is a chemical change.
2) Process - B is a chemical change.
3) Both processes A and B are chemical change
4) None of these processes is chemical change.​

Answer 1

Explanation:

1. due to the formation of CO2

2. sodium hydrogen carbonate

3. coating a layer of paint and keeping it away from the air (so that it cannot form metal oxides)

6. beacuse after the change its taste and smell change

7. in burning of wood chemical reaction take place and in cutting of wood is a physical change