Samacheer Kalvi solutions for Science [English] Class 8 TN Board chapter 10 - Changes around us [Latest edition]

Burning of paper is a ______ change.

Burning of matchstick is an example for chemical reaction caused by _______

_______ undergoes rusting.

The pigment responsible for browning of apples is ______.

Brine is a concentrated solution of ______.

Limestone contains ______ mainly.

Which of the following factor induces electrtolysis?

In Haber’s process of producing ammonia _______ is used as a catalyst.

Dissolved gases like sulphur dioxide and nitrogen oxides in rain water causes ________.

_______ is/are responsible for global warming.

Photosynthesis is a chemical reaction that takes place in the presence of ______.

Iron objects undergo rusting when exposed to _______ and _______.

_____ is the basic material to manufacture urea.

Electrolysis of brine solution gives _______ gases.

________ is a chemical substance which alters the speed of a chemical reaction.

_______ is the enzyme responsible for browning of vegetables and fruits.

A chemical reaction is a temporary reaction.

Decomposition of lead nitrate is an example for a chemical reaction caused by light.

Formation of slaked lime from quicklime is an endothermic reaction.

CFC is a pollutant.

Light energy may come out due to chemical reactions.

Match the following.

Match the following.

Define a chemical reaction.

Mention the various conditions required for a chemical reaction to occur.

Define catalysis.

What happens when an iron nail is placed in copper sulphate solution?

What is pollution?

What is tarnishing? Give an example.

What happens to the brine during electrolysis?

On heating, calcium carbonate gives calcium oxide and oxygen. Is it an exothermic reaction or an endothermic reaction?

What is the role of a catalyst in a chemical reaction?

Why photosynthesis is a chemical reaction?

Explain the environmental effects of chemical reactions?

Explain how food items are spoiled by chemical reactions?

Explain any three conditions that are required for a chemical reaction to take place. Give example.

Explain the role of yeast in making cakes and buns in a bakery?

Burning of fossil fuels is responsible for global warming. Justify the statement.

Discuss how acid rain occurs due to emission of smoke from vehicles and industries?

Is rusting good for iron materials? Explain.

Do all the fruits and vegetables undergo browning? Explain.

Classify the following day-to-day activities based on chemical reactions by physical contact, solutions of reactants, heat, light, electricity, and catalyst.

1. Burning of crackers during festivals
2. Fading of coloured clothes on drying under sunlight.
3. Cooking of eggs.
4. Charging of batteries.

Kumar is going to build a house. To purchase the iron rods required for construction, he visited an iron and steel shop nearby. The seller showed him some iron rods which are fresh and good. He also showed him little older iron rods which are brownish in appearance. The price of fresh rods is more than the older ones. The seller also gave some offers to older ones. Kumar’s friend Ramesh advised him not to buy the cheaper rods.

1. Is Ramesh right in his suggestion?
2. Could you explain the reason for his suggestion?
3. What are the values shown by Ramesh?

Palanikumar is a Lawyer. He lives in a luxurious flat. Due to high rent, he wants to shift his residence to a place where he has a chemical industry nearby. There the rent is very cheap and the area is less populated also. His son Rajasekar, studying VIII, does not like this and likes to go to some other place.

1. Is Rajasekar right in his attitude?
2. Why did he refuse to go there?
3. What are the values shown by Rajasekar?