The questions below consists of an assertion and a Reason. Use the key to choose the appropriate answer.
Q1: Assertion: Air is found everywhere.
Reason: We can feel air and we can see air.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Ans: (b)
The assertion is a correct statement. Air is a mixture of gases that surrounds the Earth and fills its atmosphere. It is indeed found everywhere on the planet.
The reason is a wrong statement. While we can feel the effects of air, such as the sensation of wind, and see its influence on things like the movement of leaves, the air itself is not directly visible or something that can be seen as a substance. The particles in air are very small and not visible to the naked eye.
Q2: Assertion: CO2 and oxygen are involved in respiration.
Reason: Plants and animals consume oxygen for respiration and produce carbon dioxide.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Ans: (a)
The assertion is a correct statement. Both carbon dioxide (CO2) and oxygen (O2) play important roles in the process of respiration. In respiration, organisms take in oxygen and release carbon dioxide as a waste product.
The reason is also a correct statement. During respiration, animals and plants do consume oxygen for cellular processes, and as a result of these processes, they produce carbon dioxide as a metabolic waste.
The reason is a correct explanation for the assertion, as it illustrates the relationship between the involvement of CO2 and oxygen in the process of respiration.
Q3: Assertion: In air, there are nitrogen, oxygen, CO2, H2O, and other gases found.
Reason: Air is the mix of different gases.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Ans: (a)
The assertion is a correct statement. The Earth's atmosphere is composed of a mixture of gases, including nitrogen, oxygen, carbon dioxide (CO2), water vapor (H2O), and traces of other gases.
The reason is also a correct statement. Air is indeed a mixture of different gases. The primary components of air are nitrogen (about 78%), oxygen (about 21%), and trace amounts of other gases like carbon dioxide and water vapor.
The reason is a correct explanation for the assertion, as it clarifies that the composition of air is a mixture of various gases.
Q4: Assertion: We cannot survive without air.
Reason: Air is not essential for respiration.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Ans: (c)
Air is indeed essential for our survival as it contains oxygen, which we breathe in during respiration.
Q5: Assertion: We feel comfortable on a windy day.
Reason: Wind is caused by the movement of air.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Ans: (b)
The movement of air causes wind, but it does not explain why we feel comfortable on a windy day. We feel comfortable because the moving air helps in evaporation of sweat from our body, thereby giving us a cooling effect.
Q6: Assertion: Plants release oxygen into the atmosphere.
Reason: Plants perform photosynthesis.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Ans: (a)
During the process of photosynthesis, plants take in carbon dioxide and release oxygen. This is why plants are able to release oxygen into the atmosphere.
Q7: Assertion: Air is a mixture of gases.
Reason: Air is made up of nitrogen, oxygen, carbon dioxide and other gases.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Ans: (a)
Air is indeed a mixture of gases, and it is made up of nitrogen, oxygen, carbon dioxide and other gases in varying proportions.
Q8: Assertion: Air pressure decreases with height.
Reason: The number of air molecules decreases as we go up.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Ans: (a)
The number of air molecules decreases as we go up, therefore the weight of the air (which causes air pressure) also decreases. This is why air pressure decreases with height.
