Air- The Envelope of Life

Q.1  Do plants respire all the time? Compare the rate of respiration and rate of photosynthesis in a day.

Ans - Plants respire all the time because their cells need energy to stay alive, but plants can only photosynthesis when they are in the light. During day time photosynthesis is more in comparison to respiration, In dim light rate of respiration and photosynthesis are equal and at night respiration is dominant.

Q2. All living beings consume oxygen, it can lead to depletion of oxygen level. Yes or No? give reason for your answer.

Ans – No, because oxygen released during photosynthesis is much more than the oxygen consumed in respiration, the net oxygen is sufficient to support and sustain all life forms of life.

Q3. From where does the Saturn’s moon Dione got oxygen?

Ans – According to study, the oxygen atmosphere on this moon is most likely a product of space particles and surface ice.

Q4. Give reason: ‘Solid carbon dioxide is called as dry ice.’

Ans – On heating, solid carbon dioxide changes directly into gas getting into the liquid form. That’s is why solid carbon dioxide is called dry ice.

Q5. What are the advantages of CNG?

Ans – CNG (compressed natural gas) is a fuel used as a substitute for petrol and diesel. It is a clean alternative to these fuels. It is low in pollutants, economical and available in abundance.

Q6. Why do mountaineers have difficulty in breathing while climbing?

Ans - When we breathe in air at sea level, the atmospheric pressure causes oxygen to easily pass through lung membranes into the blood.  At high altitudes, the lower air pressure makes it more difficult for oxygen to enter our vascular systems.

Q7. Why do helium balloons floats in air?

Ans - The helium balloon displaces an amount of air (just like the empty bottle displaces an amount of water). As long as the helium plus theballoon is lighter than the air it displaces, the balloon will float in theair. It turns out that helium is a lot lighter than air.

Q8. Name the gas that is referred to as ‘laughing gas’.

Ans – Nitrous oxide (N₂O) is known as laughing gas.

Q9. Draw a labeled diagram to show composition of air.

Ans -  

Q 10. Ravi while driving, switch off the engine of his car at red traffic light. What value is shown by Ravi.

Ans – He showed care for environment, responsible individual to avoid air and sound pollution and saving valuable fuel.