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Correct option is D) All of these

When trees on hill sides are cut, rainwater flows down the bare mountains. This causes flooding of low lying areas.

It is because sweat from our body does not evaporate easily.

The substance which accelerates the speed of a reaction without itself undergoing any change is called

1. catalyst

Correct option is C) Both A & B

Correct option is C) Anemometer

Correct option is C) Bay of Bengal

1. The water drop inflates in the refill. 

2. Because we know that air expands on heating. So. the water drop is moved upwards. Hence, there is a change in the position of the water drop.

Correct option is C) earth
 

1. We help and cooperate our neighbours. 

2. We help in making necessary arrangements to shift their essential household goods, domestic animals and vehicles etc., to safer places. 

3. We suggest them. 

a) to avoid driving on roads as flood water standing on roads might have damaged the roads. 

b) not to drink water which might have been contaminated. 

c) advise them not to touch fallen power lines and wet switches. 

d) exhorts them not to go out for fun.

Post cyclone measures: If you are staying in a cyclone hit area 

• Strictly avoid any loose and dangling wires. 
• Do not drink water that could be contaminated. Always store drinking water for emergencies. 
• Do not go out for the sake of fun. 
• Cooperate and help your neighbors and friends.

C) Anemometer and barometer

Correct option is A) Equator

Precautions to be taken before a cyclone: 

1. We should be cautious about rumours. 

2. If we feel that houses are not safe at the time of cyclone, we have move into a pucca building in the vicinity. 

3. We should keep mobile phones in a waterproof bag, fully charged. If we have more than one mobile phone, we have to use one phone at a time, leaving the other phones switched off and using them one after the other to ensure communication to the longest possible period. 

4. If we have to vacate the house close the toilet seat with sandbags. 

5. We should close the drainage holes to prevent reverse flow of sewage. 

6. The trained students should cooperate with the response teams. 

7. We should make necessary arrangements to shift essential household goods, domestic animals and vehicles, etc. to safer places. 

Cyclones – Do’s and Don’ts:

1. We should not ignore the warnings issued by the meteorological department through T.V., Radio or newspapers: Pass on the information to others and ignore rumors. 

2. When a cyclone alert is on for your area, continue normal working but stay alert to the radio warnings. 

3. We should make necessary arrangements to shift essential household goods, domestic animals and vehicles, etc. to safer places. 

4. Switch off electrical mains in your house. 

5. Keep ready the phone numbers of all emergency services like police, fire brigade, and medical centres. 

6. Pack essentials for yourself and your family to last few days, including medicines, special food for those who would need it. This may include babies and elders.

Correct option is D) Pressure

The process of burning of a substance in the presence of oxygen and releasing a large amount of light and heat is called burning.

1. Air over industrial cities has a higher amount of carbon-di-oxide in it. 

2. Air in coastal areas may have more water vapour than inland areas. 

3. Air also contains more water vapour in rainy season. 

4. The amount of dust in the air is more in windy places.

1. Preferring public transport

2. Avoid burning of substances near civilian areas.

Take two balloons of the same size, and mark them as A and B and blow them to equal size. The these ballon to the end of a meter scale. Move the balloons along the scale to balance the scale. Slowly allow the air from ballon A to escape. The scale becomes imbalanced when the air is released from ballon A and the side of the scale with ballon B goes down. This shows air has weight.

1. Air occupies space.

2. Air has weight.

1. Air is a mixture of many gases.

2. Air is one of the natural resources

3. Nitrogen occupies 78% by volume of air.

Air is mixture of several gases like Nitrogen, Oxgen, Carbon dioxide, water vapor, insert gases and dust particles.

Nitrogen occupies  78% by volume of air.

1. Nitrogen ( 78% )

2. Oxygen (21%)

3. 0.04%

4. Carbon dioxide

1. While walking an street, sometimes we feel that wind is pushing us,

2. Cloths hanged to dry them will fly here and there when wind blows.

5. Kites fly up in the sky.

1. False. 

Correct: The catalyst used in the laboratory preparation of oxygen gas from hydrogen peroxide gas is magnesium dioxide.

2. True

3. True

4. False. 

Correct: Enameling is the process of baking a mixture of silicates on the surface of iron at a high temperature.

5. True

1. Natural fixation 

2. From leguminous plants 

3. From ammonia and ammonium salts 

4. From nitric acid and nitrate salts

Uses of nitrogen: 

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 tyres of vehicles.

1. Astronauts cannot breathe in space unless they carry their own oxygen with them. 

2. They can make their own oxygen by using energy from the solar arrays to split hydrogen and oxygen from water.

1. True

2. False 

Correct statement: Oxygen is about two times more soluble in water than Nitrogen.

3. True

4. True

5. False 

Correct statement: Solid form of CO₂ is called as dry ice which undergoes sublimation.

6. True

7. False 

Correct statement: An average increase in the temperature of the atmosphere is called as global warming.

8. True

9. True

10. False 

Correct statement: Solid CO₂ gas is so cold that moisture in the air condenses on it, creating a dense fog.

Uses of oxygen:

1. It is used as oxy – acetylene light for cutting and welding metals. 

2. It is used to remove carbon impurities from steel. 

3. Plants and animals use oxygen from the air for respiration. 

4. It is used to oxidize rocket fuel. 

5. It is used for artificial respiration by scuba divers, mountaineers, astronauts, patients etc. 

6. Mixed with powdered charcoal it is used as explosives. 

7. It is used in the synthesis of methanol and ammonia.

(c) Assertion is true, but the reason is false

Oxygen is a non – combustible gas as it does not bum on its own. It supports the combustion of other substances.

Oxygen is used to remove carbon impurities from steel.

If oxygen has the capacity to bum itself, striking a match stick will be enough to bum all the oxygen in our planet’s atmosphere.

(d) Carbon dioxide

Post cyclone measures : 

If you are staying in a cyclone hit area

1. Strictly avoid any loose and dangling wires. 

2. Do not drink water that could be contaminated. Always store drinking water for emergencies. 

3. Whenever there is an outbreak of dysentery, we should take tea, decoction and starch solution (Ganji). 

4. We should not go near to bunds of tanks, streams, the river banks, fallen trees, buildings, poles and seashores to play or sight-seeing and taking selfies. 

5. Cooperate and help your neighbours and friends. First aid should be provided to the injured. 

6. At the time of cyclones, some people lose their beloved family members and children or pets. In such situations, we should give assurance, guidance and counselling in order not to go to a depressed state.

1. Uneven heating takes place on the surface of the earth. 

2. We know that regions close to the equator gets more heat from the sun. 

3. This is because of the direction of the sunlight being straighter close to the equator. 

4. The air in these regions gets warmer. 

5. The warm air rises, and the cooler air from the regions in the 0 – 30° latitude belt on either side of the equator moves in. 

6. This movement of air sets forth winds that move over the earth. 

7. We have also seen that the increased wind speed is accompanied by a reduced air pressure and this aids rains.

1. Factors like wind speed, wind direction, temperature and humidity contribute to the development of cyclones. 

2. In India cyclones usually occur in the month of May – June and October – November. 

3. More cyclones tend to occur on the eastern side i.e. towards Bay of Bengal.

Correct option is C) May – June

Correct option is B) Heating

Correct option is B) less dense

Correct option is A) Anemometer

Correct option is  C) region close to equator

Correct option is C) 48 hours

Correct option is A) Giant engines