CHEMISTRY [5 Mark Question Answer]

Ways to reduce water pollution :
1. Effluent treatment – The chemical wastes released from industries should be treated in effluent treatment plants to remove harmful chemicals present in them before discharging into water bodies like river, lake, etc.
2. Sewage treatment – Sewage should be treated in sewage treatment plants before being released into rivers.
3. Recycling of industrial wastes – Waste products from factories should be recycled and used before being released.
4. Organic farming – Excessive use of insecticides and pesticides should be reduced and organic fanning should be encouraged.
5. Biodegradable detergents – The use of synthetic detergents should be reduced and more of biodegradable detergents should be used.

The water cycle involves evaporation (and transpiration), condensation, precipitation and collection.
1. Evaporation and transpiration – Sun heats up water in rivers, lakes, seas, etc. into water vapour. Plants also add water vapour to the atmosphere through their leaves by transpiration.
2. Condensation – Water vapours being lighter rise up and condense to form water droplets (by the cool air up in the atmosphere). These droplets collect together to form clouds.
3. Precipitation – It occurs when tiny droplets in the clouds combine to form large droplets, become heavy and fall down as rain, snow, hail or sleet on the earth.
4. Collection – On the earth, water flows across land and reaches river, lake, stream, sea and also seeps through soil to form groundwater. The water from water bodies evaporate again and water cycle continues in nature.Importance of the water cycle :

1. The water cycle helps in controlling the climatic conditions.
2. It helps in restoring the water lost from the earth’s surface and maintaining the balance of water on the earth.
3. Cultivation of crops depends mostly on rainwater.

The three states of water are :

1. Solid – as ice, snow, frost, mist, etc.
2. Liquid – in oceans, seas, rivers, lakes, springs, rainwater etc.
3. Gas – as water vapour in the atmosphere

Water can be changed from one form to another, i.e., solid to liquid to gaseous state by changing the temperature. On heating, ice (solid state) melts and changes to water (liquid state). On cooling, water changes to ice. On heating, water (liquid state) boils and changes into steam (gaseous state). On cooling, steam condenses and changes back to water. Thus, the three states of water can be changed from one form to another by changing the temperature.