11. Air Around us Flashcards
Which of the following statements about air is correct?
a) Air is composed solely of oxygen and nitrogen.
b) Air is a homogeneous mixture of gases.
c) Air is a mixture of gases, including oxygen, nitrogen, carbon dioxide, and water vapor.
d) Air does not occupy space and is weightless.
Answer:
c) Air is a mixture of gases, including oxygen, nitrogen, carbon dioxide, and water vapor.
Explanation:
Air is a heterogeneous mixture of various gases, with nitrogen and oxygen being the most abundant, along with smaller amounts of carbon dioxide, water vapor, and other trace gases
Consider the following statements about air in water:
1 Aquatic plants release oxygen into the water.
2 Aquatic animals respire using dissolved oxygen in water.
3 Dissolved air in water is made entirely of carbon dioxide.
Which of the above statements are correct?
a) 1 and 2 only
b) 1 and 3 only
c) 2 and 3 only
d) All of the above
Answer:
a) 1 and 2 only
Explanation:
Aquatic plants release oxygen during photosynthesis, and aquatic animals use the dissolved oxygen for respiration. Dissolved air in water contains a mixture of gases, not just carbon dioxide.
Why is the atmosphere essential for life on Earth?
a) It protects Earth from excessive solar radiation.
b) It supplies gases necessary for life processes.
c) It maintains a balance of temperature and pressure.
d) All of the above
Answer:
d) All of the above
Explanation:
The atmosphere regulates temperature, provides gases like oxygen and carbon dioxide necessary for respiration and photosynthesis, and shields the Earth from harmful radiation.
The mutual dependency of plants and animals for gases in the atmosphere is based on which of the following processes?
a) Combustion and evaporation
b) Photosynthesis and respiration
c) Transpiration and condensation
d) Erosion and sedimentation
Answer:
b) Photosynthesis and respiration
Explanation:
Plants release oxygen during photosynthesis, which is used by animals for respiration, while animals release carbon dioxide during respiration, which plants use for photosynthesis.
Which of the following best explains why air is considered a mixture and not a compound?
a) Air has fixed proportions of its components.
b) The components of air can be separated by physical means.
c) Air is chemically bonded to form a homogeneous mixture.
d) The composition of air varies in different locations.
Answer:
b) The components of air can be separated by physical means.
Explanation:
Air is a mixture of gases that are not chemically bonded and can be separated through physical processes like fractional distillation.
Consider the following processes related to air:
1 Burning of fossil fuels
2 Photosynthesis by plants
3 Respiration in animals
4 Decomposition of organic matter
Which of the above processes increase the concentration of carbon dioxide in the atmosphere?
a) 1 and 2 only
b) 1, 3, and 4 only
c) 2 and 3 only
d) All of the above
Answer:
b) 1, 3, and 4 only
Explanation:
Burning of fossil fuels, respiration, and decomposition release carbon dioxide, whereas photosynthesis reduces it by using carbon dioxide to produce food.
What is the approximate percentage of nitrogen in Earth’s atmosphere?
a) 21%
b) 78%
c) 0.03%
d) 1%
Answer:
b) 78%
Explanation:
Nitrogen makes up about 78% of Earth’s atmosphere, while oxygen accounts for 21%.
- Which of the following phenomena would cease in the absence of oxygen in the atmosphere?
1 Combustion
2 Aerobic respiration
3 Photosynthesis
4 Decomposition by certain microbes
a) 1 and 2 only
b) 1, 2, and 4 only
c) 2 and 3 only
d) All of the above
Answer:
b) 1, 2, and 4 only
Explanation:
Combustion, aerobic respiration, and decomposition by aerobic microbes depend on oxygen. Photosynthesis, however, does not require oxygen but produces it as a by-product.
Dust particles present in the atmosphere play a significant role in which of the following processes?
a) Supporting respiration in plants and animals
b) Facilitating cloud formation through condensation
c) Increasing the oxygen content of the atmosphere
d) Reducing the temperature of the Earth’s surface
Answer:
b) Facilitating cloud formation through condensation
Explanation:
Dust particles act as nuclei around which water vapor condenses to form water droplets, leading to cloud formation.
What is the role of water vapor in the air?
1 It helps regulate Earth’s temperature through the greenhouse effect.
2 It is necessary for the process of photosynthesis.
3 It contributes to precipitation.
It is a source of nitrogen for plant growth.
a) 1, 3, and 4 only
b) 1 and 3 only
c) 2 and 4 only
d) All of the above
Answer:
b) 1 and 3 only
Explanation:
Water vapor plays a key role in regulating temperature and contributes to the water cycle, leading to precipitation. It is not directly involved in photosynthesis or nitrogen fixation.
Which of the following components of the atmosphere is critical for absorbing harmful ultraviolet (UV) radiation from the sun?
a) Carbon dioxide
b) Nitrogen
c) Oxygen
d) Ozone
Answer:
d) Ozone
Explanation:
The ozone layer in the stratosphere absorbs harmful UV radiation, protecting life on Earth.
Which of the following would happen if the concentration of carbon dioxide in the atmosphere doubled?
a) A decrease in the greenhouse effect
b) Enhanced plant growth due to more photosynthesis
c) Increased global warming and climate change
d) Stabilization of Earth’s temperature
Answer:
c) Increased global warming and climate change
Explanation:
Higher carbon dioxide levels would enhance the greenhouse effect, trapping more heat and leading to global warming and associated climate changes.
Which statement about nitrogen in the atmosphere is incorrect?
a) It forms a major component of Earth’s atmosphere.
b) It is used directly by animals for protein synthesis.
c) It is essential for the nitrogen cycle involving soil microbes.
d) It is mostly inert and does not react easily.
Answer:
b) It is used directly by animals for protein synthesis.
Explanation:
Nitrogen cannot be directly used by animals. It must first be fixed into usable compounds by bacteria or industrial processes before entering the food chain.
