Why does the temperature of a substance remain constant during its melting point or boiling point?
Comment on the following statements:
(a) Evaporation produces cooling.
(b) Rate of evaporation of an aqueous solution decreases with increase in
humidity.
(c) Sponge though compressible is a solid.
You want to wear your favourite shirt to a party, but the problem is that it
is still wet after a wash. What steps would you take to dry it faster?
It is a hot summer day, Priyanshi and Ali are wearing cotton and nylon
clothes respectively. Who do you think would be more comfortable and
why?
You are provided with a mixture of naphthalene and ammonium chloride
by your teacher. Suggest an activity to separate them with well labelled
diagram.
(a) Conversion of solid to vapour is called sublimation. Name the term used
to denote the conversion of vapour to solid.
(b) Conversion of solid state to liquid state is called fusion; what is meant
by latent heat of fusion?
Alka was making tea in a kettle. Suddenly she felt intense heat from the
puff of steam gushing out of the spout of the kettle. She wondered whether
the temperature of the steam was higher than that of the water boiling in
the kettle. Comment
Water as ice has a cooling effect, whereas water as steam may cause severe
burns. Explain these observations.
Classify the following into osmosis/diffusion
(a) Swelling up of a raisin on keeping in water.
(b) Spreading of virus on sneezing.
(c) Earthworm dying on coming in contact with common salt.
(d) Shrinking of grapes kept in thick sugar syrup.
(e) Preserving pickles in salt.
(f) Spreading of smell of cake being baked through out the house.
(g) Aquatic animals using oxygen dissolved in water during respiration.
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