Water A Precious Resource class 7 worksheet - Free Printable

Problem: Solve the water-related questions and explain the solutions.

#### Section 1: Fill in the blanks
1. a. Calcium and magnesium sulphates cause ______ hardness in water.
- Answer: Temporary
- Explanation: Calcium and magnesium sulphates cause "temporary hardness" in water because they can be removed by boiling the water. Boiling causes these compounds to precipitate out as insoluble solids (like calcium carbonate).

2. b. The purest form of water is ______.
- Answer: Distilled water
- Explanation: Distilled water is the purest form of water because it has been purified through distillation, a process that removes all impurities, leaving only pure H₂O.

3. c. The water cycle is also called as ______.
- Answer: Hydrological cycle
- Explanation: The water cycle, which describes the continuous movement of water on, above, and below the surface of the Earth, is also known as the hydrological cycle.

4. d. Saline water is usually found in ______.
- Answer: Oceans/Seas
- Explanation: Saline water, which contains high concentrations of dissolved salts, is typically found in oceans and seas. This is why ocean water is salty.

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#### Section 2: Answer the following in one word
1. a. Water that readily lathers with soap.
- Answer: Soft water
- Explanation: Soft water does not contain significant amounts of calcium or magnesium ions, so it lathers easily with soap.

2. b. The boiling point of water is ______.
- Answer: 100°C
- Explanation: The boiling point of water at standard atmospheric pressure (1 atm) is 100°C.

3. c. The area where water fills the aquifer.
- Answer: Saturated zone
- Explanation: The saturated zone is the part of an aquifer where all the pores are filled with water. It is also known as the phreatic zone.

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#### Section 3: Define
1. a. Water table
- Definition: The water table is the upper surface of the saturated zone in an aquifer. It is the level below which the soil or rock is completely saturated with water.

2. b. Rainwater harvesting
- Definition: Rainwater harvesting is the collection and storage of rainwater for various uses, such as irrigation, drinking, and other domestic purposes. It helps conserve water resources and reduce dependency on groundwater.

3. c. Non-renewable resources
- Definition: Non-renewable resources are natural resources that cannot be replenished within a human timescale. Examples include fossil fuels (coal, oil, and natural gas) and minerals. These resources are finite and deplete over time.

4. d. Infiltration
- Definition: Infiltration is the process by which water from precipitation (rain, snow, etc.) seeps into the ground and moves downward through the soil and rock layers. It is a key component of the water cycle and helps recharge groundwater.

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#### Section 4: Find the mistake in the statement and correct it
1. a. Human body is composed of 12% of water only.
- Mistake: The statement incorrectly states that the human body is composed of only 12% water. This is inaccurate.
- Correction: The human body is composed of approximately 60-70% water, depending on age, gender, and body composition.
- Corrected Statement: The human body is composed of approximately 60-70% water.

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Final Answers:

1. Fill in the blanks:
- a. Temporary
- b. Distilled water
- c. Hydrological cycle
- d. Oceans/Seas

2. One-word answers:
- a. Soft water
- b. 100°C
- c. Saturated zone

3. Definitions:
- a. Water table: The upper surface of the saturated zone in an aquifer.
- b. Rainwater harvesting: Collection and storage of rainwater for various uses.
- c. Non-renewable resources: Natural resources that cannot be replenished within a human timescale.
- d. Infiltration: The process by which water seeps into the ground and moves downward through soil and rock layers.

4. Find the mistake:
- Original statement: Human body is composed of 12% of water only.
- Corrected statement: The human body is composed of approximately 60-70% water.

Final Answer Box:
\boxed{
\begin{array}{l}
\text{1. a. Temporary} \\
\text{ b. Distilled water} \\
\text{ c. Hydrological cycle} \\
\text{ d. Oceans/Seas} \\
\text{2. a. Soft water} \\
\text{ b. 100°C} \\
\text{ c. Saturated zone} \\
\text{3. a. Water table: The upper surface of the saturated zone in an aquifer.} \\
\text{ b. Rainwater harvesting: Collection and storage of rainwater for various uses.} \\
\text{ c. Non-renewable resources: Natural resources that cannot be replenished within a human timescale.} \\
\text{ d. Infiltration: The process by which water seeps into the ground and moves downward through soil and rock layers.} \\
\text{4. Corrected statement: The human body is composed of approximately 60-70% water.}
\end{array}
}