Science M C Q

1. Gills are richly supplied with blood capillaries and can readily absorb the oxygen dissolved in water.
2. When fishes are taken out of the water, the supply of oxygen to the fishes is cut as the fishes cannot absorb and breathe using the oxygen present in the atmosphere.
3. Hence they die, when it is taken out of water.

1. In a soda bottle, carbon dioxide gas is dissolved in water under pressure.
2. The gas in the bottle expands.
3. Hence, the pressure inside the bottle increases.
4. Thus the bottle may burst in hot summer.

• Acid rain affects us in many ways. Some of the consequences are given below.

1. It irritates the eyes and skin of human beings.
2. It inhibits the germination and growth of seedlings.
3. It changes the fertility of the soil, destroys plants and aquatic life.
4. It causes corrosion of many buildings, bridges, etc.

• Preventive measures:
  Acid rain and its effects can be controlled in the following ways.

1. Minimizing the usage of fossil fuels such as petrol, diesel, etc.
2. Using CNG (Compressed Natural Gas).
3. Using a non – conventional sources of energy.
4. Proper disposal of industrial wastes.

1. Carbon dioxide (CO₂)
2. Sulphur dioxide (SO₂)
3. Phosphorus trioxide (P₂O₃) (or) Phosphorus pentoxide (P₂O₅)
4. Magnesium Oxide (MgO)
5. Iron Oxide (Fe₂O₃)
6. Sodium Oxide (Na₂O)

1. Solid carbon dioxide, called dry ice is used as a refrigerant.
2. The gas is so cold that moisture in the air condenses on it, creating a dense fog which is used in stage shows and movie effects.

Example:

Write about the reaction of nitrogen with non-metals.

3H2      +        N2          →     2NH3  

Hydrogen    Nitrogen         Ammonia

1. Liquid nitrogen is used as a refrigerant.
2. It provides an inert atmosphere for conducting certain chemical reactions.
3. It is used to prepare ammonia (by Haber’s process) which is then converted into fertilizers and nitric acid.
4. It is used for inflating the tires of vehicles.

1. Oxygen is a colorless, odorless, and tasteless gas.
2. It is a poor conductor of heat and electricity
3. Oxygen dissolves readily in cold water.
4. It is denser than air.
5. It can be made into liquid (liquefied) at high pressure and low temperature.
6. It supports combustion.