MATTER IN OUR SURROUNDINGS

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.

‘Osmosis is a special kind of diffusion’. Comment.

The non S I and S I units of some physical quantities are given in column
A and column B respectively. Match the units belonging to the same
physical quantity:
(A)                                                                   (B)
(a) degree celsius                                              (i) kilogram
(b) centimetre                                                   (ii) pascal
(c) gram per centimetre cube                              (iii) metre
(d) bar                                                              (iv) kelvin
(e) milligram                                                      (v) kilogram per metre cube

Match the physical quantities given in column A to their S I units given in
column: B
(A)                                                          (B)
(a) Pressure                                              (i) cubic metre
(b) Temperature                                         (ii) kilogram
(c) Density                                                   (iii) pascal
(d) Mass                                                   (iv) kelvin
(e) Volume                                               (v) kilogram per cubic metre

Fill in the blanks:
(a) Evaporation of a liquid at room temperature leads to a——— effect.
(b) At room temperature the forces of attraction between the particles of
solid substances are———than those which exist in the gaseous state.
(c) The arrangement of particles is less ordered in the ——— state. However,
there is no order in the ——— state.
(d) ——— is the change of gaseous state directly to solid state without
going through the ———state.
(e) The phenomenon of change of a liquid into the gaseous state at any
temperature below its boiling point is called———.

A sample of water under study was found to boil at 102°C at normal
temperature and pressure. Is the water pure? Will this water freeze at 0°C?
Comment.

Name A, B, C, D, E and F in the following diagram showing change in its state.

What produces more severe burns, boiling water or steam?

Why is ice at 273 K more effective in cooling than water at the same temperature?

Give two reasons to justify-

(a) water at room temperature is a liquid.

(b) an iron almirah is a solid at room temperature.

What is the physical state of water at--

(a) 25°C

(b) 0°C

(c) 100°C

Arrange the following substances in increasing order of forces of attraction between particles-- water, sugar, oxygen.

Give reason for the following observations.

(a) Naphthalene balls disappear with time without leaving any solid.

(b) We can get the smell of perfume sitting several metres away.

Convert the following temperatures to Kelvin scale.

(a) 25°C

(b) 373°C

Convert the following temperatures to Celsius scale.

(a) 300 K

(b) 573 K

What type of clothes should we wear in summers?

Why are we able to sip hot tea or milk faster from a saucer than a cup?

Why does our palm feel cold when we put some acetone or petrol or perfume on it?

How does water kept in an earthen pot (matka)become cool during summers?

Why does a desert cooler cool better on a hot dry day?

Suggest a method to liquefy atmospheric gases.

For any substance, why does the temperature remain constant during the change of state?

What is the physical state of water at:

(a) 250°C

(b) 100°C

Convert the following temperature to Celsius scale:

(a) 300 K

(b) 573 K

Liquids generally have lower density as compared to solids. But you must have observed that ice floats on water. Find out why.

Give reasons:

(a) A gas fills completely the vessel in which it is kept.

(b) A gas exerts pressure on the walls of the container.

(c) A wooden table should be called a solid.

(d) We can easily move our hand in air, but to do the same through a solid block of wood, we need a karate expert.

(a) Tabulate the differences in the characteristics of states of matter.

(b) Comment upon the following: rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy, and density.

The mass per unit volume of a substance is called density (density = mass/volume). Arrange the following in order of increasing density - air, exhaust from chimney, honey, water, chalk, cotton, and iron.

What are the characteristics of particles of matter?

A diver is able to cut through water in a swimming pool. Which property of matter does this observation show?

Give reasons for the following observation:

The smell of hot sizzling food reaches you several metres away, but to get the smell from cold food you have to go close.

Which of the following are matter?

Chair, air, love, smell, hate, almonds, thought, cold, cold drink, smell of perfume.