a) Is Rajasekar right in his attitude?
Yes, Rajasekar is right in his attitude.
b) Why did he refuse to go there?
A chemical industry causes air pollution, water pollution and land pollution due to its chemical wastes. So, the rate of environmental pollution around the chemical industry will be high. So it is not advisable to live in a house nearby the chemical industry. So, he refused to go there.
c) What are the values shown by Rajasekar?
Rajasekar wants his family to lead a healthy life. He wants to concentrate on his studies and achieve his goal.

a) Yes, Ramesh is right in his suggestion.
b) Could you explain the reason for his suggestion!
The older iron rods which are brownish in appearance are rusted one. Rusting is not good for iron materials. It results in the degradation of iron. Thus the rusted iron will be weakened and become brittle and flaky. So, building a house with rusted rods will degrade the strength of the building.
c) What are the values shown by Ramesh?
Ramesh is clear in his suggestion. He does not want his friend to become a prey to the shopkeeper's words. He wants his friend to be honest in his profession and not to be cheated

Photosynthesis is an irreversible change. In photosynthesis carbondioxide and water react in the presence of sunlight to produce a new substance called starch. Hence photosynthesis is a chemical reaction

Any unwanted change in physical, chemical and biological properties of the environment is termed as pollution.

When an iron nail is placed in copper sulphate solution, the blue colour of the copper sulphate solution slowly changes into green due to the formation of ferrous sulphate as a result of chemical reaction between iron and copper sulphate solution.

Chemical substance used to alter the speed of the reaction is called a catalyst and the process is called catalysis.

(i) Chemical reactions based on contact:
Certain chemical reactions take place only when the reactants are brought in contact with each other in their physical states.
Eg: When quicklime comes in contact with water, it forms slaked lime.
(ii) Chemical reactions based of solution of reactants:
When we mix two substances in solution form, the chemical reaction takes place to form new substances.
Eg: Barium chloride solution reacts with sulphuric acid solution to form barium sulphate as a white precipitate and hydrochloric acid.
(iii) Chemical reactions based on electricity:
Some chemical reactions proceed only by the passage of electricity. Such reactions are called electrochemical reaction or electrolysis.
Eg: When Brine is electrolysed it produces chlorine and hydrogen gases along with sodium hydroxide.

(i) Spoilage of food and vegetables:
Food spoilage may be defined as any change that causes food unfit for human consumption
The chemical reactions catalyzed by the enzymes result in the degradation of food quality such as development of bad tastes and odour, detorioration and loss of nutrients.
Eg: Rotten eggs develop a bad smell due to the formation of hydrogen sulphide gas.
Decaying of vegetables and fruits due to microbes.
(ii) Rancidity of fishes and meat:
Fishes and meat contains high levels of polyunsaturated fatty acids.
These fatty acids undergo oxidation when exposed to air or light.
It results in bad odour. This process is called rancidity.
(iii) Apples and fruits turn brown when cut:
It is due to chemical reaction with oxygen in air.
The cells of apples contain an enzyme called tyrosinase that when in contact with oxygen catalyses a biochemical reaction of plant's phenolic compounds to brown pigments known as melanins.

Burning fossil fuels is a cause of global warming because it produces Co, and methane. These gases give the greenhouse effect. This increase the Earth's average temperature and results in the phenomenon called Global warming.

Yeast is a biocatalyst when yeast is added while making cakes
i) it triggers fermentation
ii) it releases carbondioxide which results in the expansion of dough.
iii) it is responsible for the soft porous texture of the cake
iv) It is the keyfactor behind the characteristic bakery flavour of a cake.