Lesson 10 – More about Water
A. What’s the solution?
Due to the cold, the coconut oil in the bottle has frozen. We have to pour it out
Ans: To pour the frozen coconut oil, we need to heat the bottle so that the oil converts into liquid form.
B. Think and tell.
(1) During the rainy season, why do crisp biscuits become soft?
Ans: During the rainy season, there is more water vapour in the air. So, crisp biscuits become soft because they absorb moisture from the air.
(2) Why does water become coloured when crystals of potassium permanganate are added to it?
Ans: Water becomes coloured when crystals of potassium permanganate are added to it because potassium permanganate dissolves in it completely.
(3) When we add jaggery to water and stir it, why does the water taste sweet?
Ans: Jaggery contains sweetness. The water tastes sweet when we add jaggery to it because jaggery dissolves completely in water.
(4) The mountain peaks in the Himalayas are always covered with snow and ice. What could be the reason for that?
Ans: The reason is that the temperature in the Himalayas is much lower than in other places. So because of this cold atmosphere, the water turns into snow and ice.
C. Find out.
Why does the hot tea in a thermos flask remain hot for a long time!
Ans: The thermos flask is an airtight element, so the hot tea in a thermos flask remains hot for a long time.
D. Carry out this experiment and write about it.
Name of the experiment :
To see if rangoli dissolves in water.
Description:
I took half a glass of ______. I added a pinch of ______ to it. I stirred it with a ______
Ans: I took half a glass of water. I added a pinch of rangoli to it. I stirred it with a spoon.
What did I see?
The particles of rangoli were seen in the water, as before.
What does this mean?
_____________________________
Ans: This means that rangoli does not dissolve in water.
E. True or false?
(1) Water is transparent.
Ans: True
(2) Pure water looks bluish in colour.
Ans: False
(3) When water is heated a lot, it turns into ice.
Ans: False
(4) Sugar does not dissolve in water.
Ans: False
F. Fill in the blanks with words from the brackets.
(shape, transparent, solid, pure)
(1) ______ water has no colour, smell or taste.
Ans: Pure
(2) Water is ______
Ans: transparent
(3) Water does not have a ______ of its own.
Ans: shape
(4) Ice is the ______ state of water.
Ans: solid
G. Say why –
(1) We can see a nail that has sunk to the bottom of the water.
Ans: water is transparent, hence we can see a nail that has sunk to the bottom of the water.
(2) Sugar disappears when it is added to water and the water is stirred.
Ans: Sugar dissolves completely in water when added and stirred; therefore, it disappears in water.