Page 81 - ICSE Chemistry 6

• Blood, consis ng of water and blood cells, absorbs digested food and also helps in transporta on
of nutrients, oxygen and carbon dioxide in the body.
• Water helps in excre on of waste from the body in the form of sweat, urine or while breathing.
• Water regulates the body temperature in humans and animals. Since water has high heat capacity,
it can absorb large amount of heat energy. Also, it does not heat up or cool down as fast as land.

On hot days, we excrete water in the form of sweat. When it evaporates, it takes away heat from our
body. This lowers our body temperature and thus causes cooling. An average human loses approximately
2.5–3 litres water per day in the form of sweat, urine or while breathing. Therefore, we should drink 3–4
litres water daily to make up for this loss.

About 3–4 litres About 0.5–1 litre through
through drinking sweating

About 1 litre About 1.5–2 litres through
through food urination

About 0.25 litre About 0.5 litre through
produced by exhalation
human body

Fig. 4.6: Gain and loss of water in human beings

About 30% of a plant’s body weight is water. Water is important for plants in the following ways.

• A large amount of water is needed by plants during photosynthesis.
• Water helps in transporta on of minerals among diff erent parts of plant body.

• Water is very important for germina on of seeds.
• Plants also lose water con nuously through leaves during transpira on.

Water also serves as a habitat for aqua c organisms. For example, fi sh, whales and dolphins are water
animals and Hydrilla, lotus and water chestnut are water plants.
Some other uses of water are as follows.

• Water is used for bathing, cleaning and washing.

• A large amount of water is used in agriculture.
• A large amount of water is required in industries such as chemical industries, paper mills, petroleum
refi neries, fer lisers, steel and rayon industries.
• Water acts as a coolant in car radiators powerhouses which Coolant
generate electricity from fossil fuels and nuclear fuels. A fl uid which is used to cool a
system by transferring heat away
• Water is used for ex nguishing fi re.
from one part to another is called
• Many people in Kashmir and Kerala make homes and live in coolant.
houseboats.

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