All questions of Air and Water for Class 5 Exam

Sedimentation - this is the process by which allows particles to settle down at the bottom.

Answer:

Substances that do not dissolve in water are called insoluble substances. Baking soda is an example of an insoluble substance. The reason why baking soda does not dissolve in water is because it is a base and bases do not dissolve in water.

Explanation:

Insoluble substances are those substances that do not dissolve in water. They are usually non-polar or have a low polarity. When a substance is insoluble in water, we can say that it does not dissolve in water and does not form a solution.

There are different reasons why a substance may not dissolve in water. For example, some substances may be polar and have a high polarity, but they may not dissolve in water because they are too large to fit between the water molecules. Other substances may be non-polar and have a low polarity, which makes them unable to dissolve in water.

Baking soda is an example of an insoluble substance. It is a base, and bases do not dissolve in water. Baking soda is a compound made of sodium, hydrogen, carbon, and oxygen. When baking soda is mixed with water, it does not dissolve but rather forms a suspension. A suspension is a mixture in which the particles of a substance are dispersed throughout a liquid but are not dissolved in it.

Conclusion:

In conclusion, baking soda is an example of an insoluble substance. It does not dissolve in water because it is a base and bases do not dissolve in water. Other examples of insoluble substances include sand, oil, and chalk.

Explanation:

Heat causes the molecules in a substance to move faster, increasing the amount of space between them. This is why heating a balloon causes it to expand. When the balloon is placed over the mouth of a cold drink bottle, it is slightly stretched due to the pressure of the air inside the bottle. When the bottle is placed in hot water, the air inside the bottle heats up, causing the pressure to increase. This increased pressure causes the balloon to expand.

Therefore, putting the cold drink bottle with the capped balloon in hot water can lead to an increase in the size of the balloon.

Summary:

- Heating causes molecules to move faster.
- Heating a balloon causes it to expand.
- Placing the bottle in hot water causes the air inside the bottle to heat up, increasing the pressure and causing the balloon to expand.

Atmosphere

It is wrong, air is definitely needed for burning. Because without air the fire cannot burn.

Water is known as the universal solvent because it can dissolve many substances. Water has a unique chemical structure that allows it to interact with a wide range of compounds and dissolve them, making it a very effective solvent. Water is able to dissolve a wide variety of substances, including minerals, gases, and organic compounds, which makes it a very important substance in many chemical reactions and processes. Water is also a good solvent because it is widely available, inexpensive, and non-toxic, which makes it a popular choice for many applications.

Air exerts pressure can be shown by the example of sucking up water using a straw.











Air exerts pressure on objects and surfaces. When we suck up water using a straw, the air pressure outside the straw pushes the water up to fill the space left by the air that was sucked out. This is an example of how air exerts pressure.

When you suck the air out of the straw, the pressure inside the straw decreases. This creates a difference in pressure between the inside of the straw and the outside atmosphere. The higher atmospheric pressure pushes the lassi up into the straw. Thus, the key factor is that the air pressure inside the straw becomes lower than the atmospheric pressure, allowing the lassi to rise.

Atmospheric Pressure and Altitude

Atmospheric pressure refers to the force exerted by the weight of the air above us. The pressure decreases as we move away from the surface of the earth. Therefore, when we go up in the sky or increase altitude, the atmospheric pressure changes.

Decrease in Atmospheric Pressure with Altitude

As we climb higher, the air molecules become less dense, and the atmosphere becomes thinner. This means that there are fewer air molecules above us, and the pressure decreases. The decrease in pressure with altitude is not linear, and the rate of decrease depends on several factors, including temperature, humidity, and weather conditions.

Effects of Decreased Atmospheric Pressure

The decrease in atmospheric pressure with altitude can have several effects on our body, including:

- Ear popping: As we ascend, the pressure inside our ears changes, and we may feel discomfort or pain. This can be alleviated by swallowing, yawning, or chewing gum.

- Altitude sickness: At high altitudes, the decreased pressure can lead to altitude sickness, a condition that affects some people. Symptoms of altitude sickness include headache, nausea, dizziness, and shortness of breath.

- Boiling point of water: The decrease in pressure also affects the boiling point of water. At high altitudes, water boils at a lower temperature, which can affect cooking times and recipes.

In conclusion, when we go up in the sky, the atmospheric pressure decreases. This can have several effects on our body and the environment, and it is important to be aware of these changes when traveling to high altitudes.

Explanation:
When a block of wood is placed in fresh water, it floats because the density of wood is less than that of water. However, when the same block of wood is placed in saline water, the density of the water increases due to the presence of salt in it. As a result, the block of wood will float at a higher level in saline water.

Reason:
The reason for this is that the density of saline water is higher than that of fresh water. The increase in density is due to the presence of salt in the water. The increased density of the water exerts a greater upward buoyant force on the block of wood, causing it to float at a higher level.

Conclusion:
Therefore, the correct answer is option C - the block of wood will float at a higher level in saline water.

The water cycle is an important method to rejuvenate the freshwater resources. It involves the evaporation of water into water vapour by the heat of the sun which further condenses into tiny water droplets which fall on earth as rain. Thus, the process, such as, evaporation and condensation and precipitation plays an important role.

Introduction:
The atmosphere is a layer of gases that surrounds the Earth. It plays a vital role in supporting life on our planet. The atmosphere is made up of different components, including air, water vapor, and dust particles. Among these components, the most significant and abundant one is air.

Explanation:
Air: The atmosphere is mainly comprised of air, which is a mixture of gases. The most abundant gases in the air are nitrogen (78%) and oxygen (21%). These gases are crucial for sustaining life on Earth. Nitrogen is necessary for plant growth, while oxygen is essential for respiration in animals, including humans.

Water Vapor: While the atmosphere is primarily composed of air, it also contains water vapor. Water evaporates from oceans, lakes, rivers, and other water bodies and rises into the atmosphere as an invisible gas. This process is called evaporation. Water vapor in the atmosphere plays a crucial role in the water cycle, which is responsible for distributing water across the Earth.

Land: The land, which includes the Earth's solid surface, is not a part of the atmosphere. The atmosphere extends above the land and covers the entire planet. However, the land interacts with the atmosphere in various ways. For example, land surfaces absorb and reflect solar radiation, influencing temperature patterns in the atmosphere.

All of these: Since the atmosphere consists of air and water vapor, which are present in the form of gases, the correct answer to the question is "All of these." The atmosphere encompasses the air we breathe and the water vapor that exists in the gaseous state. It does not include the land, which is a solid substance.

Conclusion:
In conclusion, the atmosphere is the part of the Earth that is composed of air and water vapor. It is responsible for providing the gases necessary for life and plays a crucial role in regulating the Earth's climate.

Answer:
The correct representation of the composition of air is given by option D. Let's break down the composition of air and analyze each option:
Option A:
- P represents Nitrogen, but it is incorrectly shown as the most abundant gas in the air.
- Q represents Oxygen, but it is shown as the least abundant gas, which is incorrect.
- R represents an inert gas, which is not present in the composition of air.
- S represents Carbon dioxide, but it is shown as the second most abundant gas, which is incorrect.
Option B:
- P represents Nitrogen, but it is shown as the least abundant gas, which is incorrect.
- Q represents Oxygen, but it is shown as the most abundant gas, which is incorrect.
- R represents an inert gas, which is not present in the composition of air.
- S represents Carbon dioxide, but it is shown as the second most abundant gas, which is incorrect.
Option C:
- P represents Nitrogen, but it is shown as the least abundant gas, which is incorrect.
- Q represents Oxygen, but it is shown as the most abundant gas, which is incorrect.
- R represents an inert gas, which is not present in the composition of air.
- S represents Carbon dioxide, but it is shown as the second most abundant gas, which is incorrect.
Option D:
- P represents Nitrogen, and it is correctly shown as the most abundant gas in the air.
- Q represents Oxygen, and it is correctly shown as the second most abundant gas.
- R represents an inert gas, which is not present in the composition of air.
- S represents Carbon dioxide, and it is correctly shown as a minor component of air.
Therefore, option D is the correct representation of the composition of air.