A Journey through States of WaterClass 6 Science NCERT Solutions
10 Solutions
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Solution 1 of 10
Q1Let us enhance our learning
Which of the following best describes condensation?
(i)
The conversion of water into its vapour state.
(ii)
The process of water changing from a liquid into gaseous state.
(iii)
The formation of clouds from tiny water droplets.
(iv)
The conversion of water vapour into its liquid state.
Solution
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."
Q2Let us enhance our learning
Identify in which of the given processes, evaporation is very important-
(i)
Colouring with
(a)
crayons
(b)
water colours
(c)
acrylic colours
(d)
pencil colours
(ii)
Writing on paper with
(a)
pencil
(b)
ink pen
(c)
ball point pen
Solution
(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) in it evaporates.
Q3Let us enhance our learning
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 find out why?
Solution
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 cannot undergo evaporation to produce a cooling effect. Hence, the space around natural grass feels cooler than around plastic grass.
Q4Let us enhance our learning
Give examples of liquids other than water that evaporate.
Solution
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.
Q5Let us enhance our learning
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 warmer. Normally, when water evaporates, it requires heat, not cold air. What do you think about this?
Solution
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 increase the rate of air movement over the wet clothes. This increased air movement carries away the water vapour more quickly, thereby speeding up the evaporation process. Even though the air from the fan is not warm, the faster evaporation still leads to faster drying of clothes because the water rapidly changes into vapour, taking heat from the clothes and the surrounding air.
Q6Let us enhance our learning
Usually, when sludge is removed from drains, it is left in heaps next to the drain for days. Afterward, it is transported to a garden or a field where it can be used as manure. This approach reduces transportation cost of the sludge and enhances the safety of individuals handling it. Reflect upon it and explain how.
Solution
Sludge removed from drains contains a significant amount of water. When it is left in heaps for 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 reduction in mass and volume directly leads to lower transportation costs, as less material needs to be moved. Additionally, drier sludge is less messy and easier to handle, thereby enhancing the safety and convenience for individuals involved in its transportation and application as manure.
Q7Let us enhance our learning
Observe the activities in your house for a day. Identify the activities that involve evaporation. How does understanding the process of evaporation help us in our daily activities?
Solution
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 from our body.
\end{itemize}
Understanding the process of evaporation helps us in daily activities by:
\begin{itemize}
\item Knowing how to dry clothes faster (e.g., spreading them out, hanging them in sunlight or a windy place, as discussed in the chapter).
\item Explaining why sprinkling water on a hot floor cools it down, due to the cooling effect of evaporation.
\item Understanding the cooling effect in earthen pots (matka/surahi) for storing water.
\item Explaining why hand sanitiser dries quickly on hands.
\end{itemize}
Q8Let us enhance our learning
How is water present in the solid state in nature?
Solution
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, and hail.
Q9Let us enhance our learning
Reflect on the statement "Water is our responsibility before it is our right." Share your thoughts.
Solution
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 "The increasing demand for water causes its shortage in many parts of the world." Therefore, it is our collective and individual responsibility to conserve water, prevent its pollution, and use it wisely to ensure its availability for everyone, including future generations. This includes avoiding wastage and keeping water bodies clean, as mentioned in the chapter: "it is very important to use water wisely and avoid wasting it. Let us keep our water bodies free from pollution." Only by fulfilling this responsibility can we truly assert our right to water sustainably.
Q10Let us enhance our learning
The seat of a two-wheeler parked on a sunny day has become very hot. How can you cool it down?
Solution
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, similar to how sprinkling water on a floor or roof during summer cools it, as described in the chapter.