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(c) calcium bicarbonate

(a) The crystals of washing soda quickly lose water molecule

Magnesium sulfate crystals are commonly called Epsom slat.

1. I shall educated the members of my house to keep the house and surroundings clean and neat. 

2. I request the neighbours not to throw away their house hold wastes on roads or at any place of their choice. 

3. I shall suggest them to separate organic and inorganic wastes and hand over to the people who collect these waste materials. 

4. I propagate the importance of sanitation by mouth and also with my friends. 

5. I cooperate with all organisations who work in this direction.

Correct option is B) Chlorine

1. Chlorine and 

2. Ozone are the two chemicals used to disinfect the water.

1. Sanitation plays a major role in keeping good health for the public. 

2. If the sanitation is poor* both water and air becomes polluted. 

3. Public depend upon these two items for their healthy living. If they are contaminated public health becomes a big threat. 

4. Neglected sanitation leads to diseases in the people living nearby.

Large objects like rags, sticks, cans, plastic packets… etc in waste water are removed by the bar screens in a waste water treatment plant.

Water content in human body is

1. 70% 

1. True

2. True

3. False. 

Correct — On boiling water exists in the gaseous state.

4. False. 

Correct — Respiration add up water to the atmosphere.

5. False. 

Correct — Well water exists above the impervious rocky layers of earth.

6. False. 

Correct — Sodium carbonate and sodium sulphate form an aqueous solution.

7. True

8. True

9. False. 

Correct — Water from rivers and lakes is impure water.

10. True

1. Rain water is the purest form of water. It may dissolve gases like carbon dioxide forming weak acids. 

2. Water generates electricity in hydroelectric power stations and steam in boilers for industrial applications. 

3. Water is added to the atmosphere by burning of fossil fuels and respiration by living organisms. 

4. If potassium nitrate is added to water in a beaker to give a homogeneous mixture, then potassium nitrate is referred to as the solute, water as the solvent and the homogeneous mixture as the solution. 

5. Water fit for human consumption and drinking purposes is called potable water.

(a) Water is a universal; solvent. 

(b) Rainwater is the purest form of natural water. 

(c) Sand and dust are suspended impurities in water. 

(d) Sea water has high concentration of salt (impurity). 

(e) Water covers nearly 4 / 5 th of the surface of the earth. 

(f) Evaporation of rain water leaves NO residue. 

(g) Potash alum is the chemical added to water to remove the tiny suspended particles. 

(h) A solution is a uniform mixture of a solute and a solvent. 

(i) Ice, water and steam have different physical states but are chemically identical. 

(j) Boiling kills most of the germs in water. 

(k) The elements present in the molecules of water are hydrogen and oxygen.

Rain water is the purest form of water as it is distilled water i.e. water from surface of earth has evaporated and then vapours condense in the atmosphere.

Chemically pure water for laboratories is obtained-by distillation. Distilled water does not contain any salt or mineral

Sewage water carries microorganisms that spread diseases.

Adding bleaching powder to water, kills germs and harmful bacteria and viruses present in water.

Correct option is (a) poisonous

The waste water of a city or town is collected and let into a water body at a convenient location.

Correct option is (c) purified

Correct option is (b) disease

Correct option is (a) convenient

correct option is C) 70%

Correct option is (b) polluted

(a) Water has a high specific heat. Water neither heats up or cools down quickly. This property makes water an excellent cooling agent. 

(b) Water pipes burst in severe winter because the water inside I the pipes freezes and increases its volume. 

(c) Water boils at a lower temperature in the hills, where the atmospheric pressure is lower than in the plains. This is why it takes a longer time to cook in hilly regions. 

(d) Ice has a low density as compared to water. Water has the maximum density at 4°C. That is why ice floats on water. 

(e) There are impurities dissolved in seawater which increases the freezing point. That is why sea water does not freeze at 0°C.

(a) The boiling point of water increases with an increase, in pressure.

(b) Any impurity present in water lowers its freezing point and raises its boiling point.

For example, salt is added to ice to lower its melting point. Such a mixture is called a freezing mixture. The meeting is called a freezing mixture is about -15° C.

Kaveri, Tungabhadra, Sharavati, Malaprabha, Kali River, Netravathi, Bhadra, Tunga River.

Ocean, Rivers, Wells, Ponds.

Groundwater, surface water (streams, rivers, lakes, reservoirs)

Only 2.5 – 2.75 % is freshwater.

Steps to avoid pollution of water are : 

(a) Harmful wastes such as oils & chemicals should not enter into the water. 

(b) Proper toilets & sewage systems should be used to prevent human excreta, containing disease causing organisms to enter into the water. 

(c) Washing of clothes & bathing should be avoided near water sources. 

(d) Planting of trees near water sources including river banks also minimizes pollution. 

(e) To minimize thermal pollution the water should be cooled before being discharged as a waste. 

(f) Man should be made aware through various awareness programmes & media about the harmful effects of water pollution & ways to control it.

(a) Chemical pollution — A large number of industrial chemicals which include chemicals from paint, textile & dyestuff industry & various acids & salt solutions enter into water when discharged as industrial wastes. 

Chemical pollutants include — Metallic salt solutions of mercury & lead which cause heavy devastation of marine & plant life. 

Agricultural wastes include — Poisonous pesticides namely fungicides & insecticides which may also enter underground water through the soil. 

(b) Thermal pollution — Certain industries such as the iron & steel industry & numerous chemical plants use large amounts of water for varied functions. The discharged waste water after going through technical processes – is rendered hot & on entering streams of natural water – enhance growth of harmful biological organisms.

Magnesium; Hydrogen.

Mg + H₂O → MgO + H₂

(a) magnesium bicarbonate

(a) False. 

Correct — Solubility of most solids – increase in temperature.

(b) False. 

Correct — Drinking water is potable water.

(c) True

(a) The gases which are soluble in water are Carbon dioxide and chlorine 

(b) The gases which are not soluble in water are Nitrogen, hydrogen

Water obtained from different places has several salts dissolved in it, therefore, water has different taste even though pure water is tasteless.

Potassium, sodium

Two gases found dissolved in natural water are oxygen and carbon dioxide

1. d 

2. a 

3. b 

4. c

(a) Water has maximum density and minimum volume at 4°C.

(b) Freezing mixture contains ice and salt.

(c) The solubility of a gas in water increases with rise in temperature and decreases with rise in pressure.

(d) Rain water is the purest form of natural water.

(e) Use of excessive fertilizers by farmers causes water pollution.

(f) Boiling removes the temporary hardness of water.

(g) Water turns the color of anhydrous copper sulphate blue.

(h) Water turns the color of anhydrous copper sulphate scum.