Class 5 Science - Air and Water - CBSE Worksheets Solutions - 1

Multiple Choice Questions (MCQs)

(i) What is the primary gas that makes up the atmosphere by volume?

A. Oxygen
B. Nitrogen
C. Carbon Dioxide
D. Argon

Ans: B.
Nitrogen makes up about 78% of the Earth's atmosphere by volume. It is the most abundant gas in the atmosphere and is essential for life as it is a key component of proteins and DNA. While oxygen is also important for respiration, nitrogen is the dominant gas in the air.

(ii) Which layer of the atmosphere do jet airplanes typically fly in?

A. Troposphere
B. Stratosphere
C. Mesosphere
D. Thermosphere

Ans: B.
Jet airplanes typically fly in the stratosphere, which is located about 10 to 50 kilometers above the Earth's surface. This layer has very little air and is much less turbulent, making it ideal for flying. The stratosphere also contains the ozone layer, which protects us from harmful UV radiation.

(iii) What percentage of air is composed of oxygen?

A. 78%
B. 21%
C. 0.03%
D. 1%

Ans: B.
Oxygen makes up approximately 21% of the Earth's atmosphere. While nitrogen (78%) is the most abundant gas, oxygen is critical for respiration in most living organisms. Carbon dioxide, argon, and other gases make up the remaining portion.

(iv) Which layer of the atmosphere contains the ozone layer?

A. Troposphere
B. Stratosphere
C. Exosphere
D. Mesosphere

Ans: B.
The ozone layer is located in the stratosphere, about 15 to 35 kilometers above the Earth's surface. This layer absorbs most of the sun's harmful ultraviolet (UV) radiation, protecting life on Earth from UV-induced damage such as skin cancer and eye problems.

(v) What method is used to separate soluble impurities from water?

A. Filtration
B. Sedimentation
C. Evaporation
D. Decantation

Ans: C.
Evaporation is used to separate soluble impurities, such as salt, from water. When water is heated, it turns into steam, leaving the dissolved substances behind. This process is commonly used to obtain salt from seawater, as the water evaporates and the salt remains in the container.

True-life Applications

(i)How does air pressure help in the functioning of a straw?

Ans: Air pressure helps in the functioning of a straw by creating a difference in pressure inside the straw and outside it. When you suck on a straw, you decrease the air pressure inside it. The higher air pressure outside the straw pushes the liquid up into the straw, allowing you to drink.

(ii)  Why do we need to purify drinking water before use?

Ans: We need to purify drinking water to remove harmful impurities, including germs, dirt, and chemicals that can cause diseases. Water from rivers, lakes, or wells may contain harmful substances, so purification methods like filtration, boiling, or chlorination ensure the water is safe for consumption.

Label the following Diagram

Ans: 

Compare and Contrast

(i) Soluble Impurities vs Insoluble Impurities

Ans: Differences:

• Dissolving Ability: Soluble impurities dissolve in water, while insoluble impurities do not.
• Separation Methods: Soluble impurities require more complex methods like evaporation or distillation to be removed, while insoluble impurities can be easily removed using filtration or sedimentation.

(ii) Sedimentation vs Filtration
Ans: 

Differences

• Process: Sedimentation is the process of settling heavier particles at the bottom, while filtration uses a physical barrier (filter paper) to remove impurities.
• Use: Sedimentation is typically used in larger water treatment plants, while filtration can be seen in daily tasks like tea making.
• Types of Impurities Removed: Sedimentation mainly removes insoluble impurities, while filtration can remove both insoluble and some soluble impurities.

(iii) Stratosphere vs Troposphere

Ans: 

Differences

• Ozone Layer: The stratosphere contains the ozone layer, which the troposphere does not.
• Weather: Weather systems like clouds and storms are found in the troposphere, whereas the stratosphere is primarily clear with very little moisture.
• Altitude: The stratosphere starts higher than the troposphere, extending from 10 km to 50 km, while the troposphere extends from the surface to about 10 km.
• Jet Flight: Commercial jets typically fly in the stratosphere but remain in the troposphere for most of the weather-related phenomena

Project/Activity-based Questions

(i) Create a small model to demonstrate how the process of evaporation works.

Ans:

Aim: To separate salt from a mixture of salt and water through evaporation.

Materials required: Salt solution in a beaker, a shallow bowl

Procedure:

1. Pour the salt solution into the shallow bowl.

2. Keep the bowl under the sun and let the water evaporate. It may take

more than one day to evaporate.

3. Record your observations.

Inference: Salt crystals are seen in the bowl when the water evaporates.

The heat from the sun evaporates much of the water. But the dissolved

salts settle as crystals.

Conclusion: Evaporation results in the separation of salt from water.

(ii) Create a model to demonstrate how air pressure works in everyday life (e.g., using a straw).

Ans:

Materials Needed: A clear straw, a glass of water, and a plastic bottle.

Procedure:

1. Fill the glass with water.
2. Insert the straw into the water-filled glass.
3. Place your finger over the top of the straw and lift it out of the glass.
4. Now release your finger and observe what happens.

Observation:When you release your finger, the water stays inside the straw for a short period. This demonstrates how air pressure from the outside pushes the liquid up into the straw when you reduce pressure inside.

Conclusion:The air pressure around us is always pushing, and when we reduce the pressure inside the straw, air pressure helps pull the liquid up.

(iii) Write a report on how air pressure is used in different everyday tools. (e.g., a medicine dropper, fountain, or lift pump)

Ans:

Title: Air Pressure in Everyday Life

Introduction:Air pressure is used in many everyday tools that we interact with, from the simple act of drinking through a straw to complex machinery like lift pumps.

Body:

1. Medicine Dropper:A medicine dropper uses air pressure to draw liquid into the tube. When we squeeze the bulb, we push air out, and when we release it, the higher external air pressure pushes the liquid into the dropper.

2. Fountain:A fountain uses air pressure to force water up through tubes. By blowing air into the system, pressure inside the container builds up, pushing the water upward.

3. Lift Pump:Lift pumps or hand pumps work using air pressure to draw water from underground or a well. By creating lower pressure inside the pump, the surrounding air pushes the water into the pump, making it accessible.

Conclusion:These examples show how air pressure plays a vital role in making many of our everyday tools and machines work efficiently.

(iv) Conduct an experiment to show that air is needed for burning.

Ans:

Materials Needed: Two candles, a lighter, and a glass tumbler.

Procedure:

1. Place both candles on a table and light them.
2. Now, take one glass tumbler and cover one of the candles with it while leaving the other exposed to air.
3. Observe what happens.

Observation:You will see that the candle under the glass tumbler gets extinguished after a few seconds, while the other candle keeps burning. This is because the candle inside the glass is deprived of oxygen, which is necessary for burning.

Conclusion:This experiment shows that air, specifically oxygen, is essential for burning. Without it, the fire cannot continue.

(v) Make a simple model to show how filtration works in purifying water.

Ans:

Materials Needed: A funnel, filter paper, a glass of muddy water, and a clean glass for the filtered water.

Procedure:

1. Fold the filter paper into a cone and place it inside the funnel.
2. Pour the muddy water into the filter paper.
3. Wait for the clear water to collect in the glass below.

Observation:The filter paper will trap the dirt, and the clear water will pass through, demonstrating how filtration works to remove insoluble impurities from water.

Conclusion:This activity shows how filtration is used to purify water by removing solid impurities, leaving clean water behind.