Science [1 Mark Questions]

Reason : Most of the earth’s ozone is contained in the stratosphere, a layer of the atmosphere 10 – 40 km above the surface of the earth.

Reason : Brine is electrolysed to produce chlorine and hydrogen gases along with sodium hydroxide. Such reactions are called as electrolysis.

Reason : Some chemical substances are used to alter the speed of a chemical reaction. Example : metallic iron is used as a catalyst in the manufacture of ammonia.

i. b
ii. c
iii. d
iv. a

i. d
ii. a
iii. b
iv. c

i. b
ii. a
iii. d
iv. c

No. Rusting is not good for iron materials. Rust is a form of iron oxide. It occurs when iron combines with the oxygen in the air causing it to corrode. Rust can affect iron and its alloys. It makes them weaker, by replacing the strong iron with flaky powder.

The combustion of fossil fuels also releases a large amount of carbon dioxide into the atmosphere. Carbon dioxide is a greenhouse gas which is responsible for global warming. Humans bum fossil fuels, releasing huge amounts of carbon pollution and trapping more and more heat in the atmosphere.

Substances used to alter the speed of a chemical reaction, are called catalysts. For example, metallic iron is used as a catalyst in the manufacture of ammonia by Haber’s process.

Endothermic reaction.

A concentrated solution of sodium chloride called Brine is electrolyzed to produce chlorine and hydrogen gases along with sodium hydroxide. This is a very important reaction to produce chlorine industrially.

Unwanted change in physical, chemical, and biological properties of the environment. This is termed pollution.

When iron nail is dipped in the solution of copper sulphate, copper is displaced by iron and forms ferrous sulphate. Thus, the blue colour of copper sulphate changes into green because of formation of ferrous sulphate.

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

Chemical changes are otherwise called chemical reactions because one or more substances (Reactants) undergo a reaction to form one or more new substances (Products).
Reactant(s) → Product(s)