Question 1

Q1: Which of the following best describes condensation? (i) The conversion of water into its vapour state. (ii) The process of water changing from a liqui...

Accepted Answer

The correct option is (iv) The conversion of water vapour into its liquid state. As per the chapter, "The process of conversion of water vapour into its liquid state is called condensation."

Question 2

Q10: The seat of a two-wheeler parked on a sunny day has become very hot. How can you cool it down?

Accepted Answer

To cool down a hot two-wheeler seat, one can sprinkle water on its surface. The water will absorb heat from the hot seat and then evaporate. As the water evaporates, it takes away a significant amount of heat, leaving the seat cooler. This is an application of the cooling effect of evaporation, simi...

Question 3

Q2: Identify in which of the given processes, evaporation is very important- (i) Colouring with (a) crayons (b) water colours (c) acrylic colours (d) penc...

Accepted Answer

(i) Evaporation is very important in colouring with (b) water colours. Water in the water colours needs to evaporate for the colours to dry on the paper. (ii) Evaporation is very important in writing on paper with (b) ink pen. The liquid ink from the pen dries on the paper as the water (or solvent)...

Question 4

Q3: We see green coloured plastic grass at many places these days. Space around natural grass feels cooler than space around the plastic grass. Can you fi...

Accepted Answer

Natural grass contains water, which evaporates from its surface through a process called transpiration. This evaporation causes a cooling effect, similar to how water in an earthen pot cools down, as explained in the chapter. Plastic grass, on the other hand, does not contain water and therefore can...

Question 5

Q4: Give examples of liquids other than water that evaporate.

Accepted Answer

Based on the chapter, an example of a liquid other than water that evaporates is hand sanitiser. The chapter states: "Hand sanitiser disappears as you rub it on your hands. What happens to it?" This implies that sanitiser evaporates.

Question 6

Q5: Fans move air around, creating a cooling sensation. It might seem strange to use a fan to dry wet clothes since fans usually make things cooler, not w...

Accepted Answer

The chapter explains that "With the increase in the movement of air, water evaporates faster." It also states that "Evaporation causes cooling effect." When water evaporates, it absorbs latent heat from its surroundings, which leads to a cooling effect. Fans do not make the air warmer; instead, they...

Question 7

Q6: Usually, when sludge is removed from drains, it is left in heaps next to the drain for $3-4$ days. Afterward, it is transported to a garden or a field...

Accepted Answer

Sludge removed from drains contains a significant amount of water. When it is left in heaps for $3-4$ days, the water present in the sludge evaporates due to exposure to air and sunlight. As water evaporates, the sludge becomes drier, which significantly reduces its overall mass and volume. This red...

Question 8

Q7: Observe the activities in your house for a day. Identify the activities that involve evaporation. How does understanding the process of evaporation he...

Accepted Answer

Activities in the house that involve evaporation include: \begin{itemize}     \item Drying wet clothes after washing.     \item Drying of a mopped floor.     \item Drying of water left on utensils after washing.     \item Evaporation of water from open containers or spills.     \item Drying of sweat...

Question 9

Q8: How is water present in the solid state in nature?

Accepted Answer

In nature, water is present in the solid state as ice. The chapter mentions that "In the solid state, it exists as ice." It also states that "Under special conditions, it might also fall as hail or snow." Therefore, water is found in solid forms such as ice (e.g., glaciers, polar ice caps), snow, an...

Question 10

Q9: Reflect on the statement "Water is our responsibility before it is our right." Share your thoughts.

Accepted Answer

The statement "Water is our responsibility before it is our right" emphasizes that while access to water is fundamental for life, it comes with a crucial obligation. The chapter highlights that "Only a small portion of water available on the Earth is fit for use by plants, animals and humans." and "...

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