Why is iron heated in a blacksmith's furnace until it is red-hot?
Important Questions on Changes Around Us
Complete the sentence by selecting the right option after reading the paragraph.
Salt, Cement, Sand and Sawdust were playing together when Water came along. "May I join you?", asked Water.
"No.", said Salt. " My mother said that if I play with you I will
Salt, Cement, Sand and Sawdust were playing together when Water came along. “May I join you?”, asked Water.
“No,” said Cement. My mother said that if I play with you, I will.
Salt, Cement, Sand and Sawdust were playing together when Water came along. "May I join you?", asked Water.
"No," said, Sand. " My mother said that if I play with you I will
Salt, Cement, Sand and Sawdust were playing together when Water came along.
"May I join you?", asked Water.
"No" said Sawdust.
"My mother said that if I play with you I will
i) Salt, Cement, Sand and Sawdust were playing together when Water came along. "May I join you?", asked Water. Following are the responses of the four:
(a) "No.," said Salt. " My mother said that if I play with you I will (dissolve / contract)."
(b) "No.," said Cement. " My mother said that if I play with you I will (harden / melt)."
(c) "No.," said, Sand. " My mother said that if I play with you I will (dissolve/settle at the bottom)."
(d) "No.," said Sawdust. " My mother said that if I play with you I will (evaporate/float on the top)."
Which of the four changes described in (i) is an irreversible change? Explain your answer.
Two glasses are filled with water to the same level. Half a spoonful of oil is poured into one of them.
The two glasses are then placed on a window sill. What will you observe after two days?
(i) The water level in the glass without oil is higher than the other.
(ii) The water level in the glass with oil is higher than the other.
(iii) Both glasses have the same amount of water.
Give reasons for your answer.
