IMO Practice Test — Matter in Our Surroundings
14 Questions • 15 min • Olympiad level
15:00
Question 1 of 14
Assertion: Gases can be compressed easily. Reason: Gas particles have large spaces between them. Choose the correct option.
Both true, reason explains assertion
Both true, reason does not explain assertion
Assertion true, reason false
Assertion false, reason true
Explanation: Large inter-particle spaces are exactly why gases compress easily, so the reason explains the assertion.
Question 2 of 14
A solid melts at 80°C and boils at 218°C. Its melting point and boiling point in Kelvin are:
353 K and 491 K
80 K and 218 K
273 K and 373 K
353 K and 218 K
Explanation: 80 + 273 = 353 K and 218 + 273 = 491 K.
Question 3 of 14
During the boiling of water, the heat supplied is used to:
raise the temperature only
break inter-particle forces at constant temperature
increase pressure
speed up condensation
Explanation: The latent heat of vaporisation breaks the forces between particles while the temperature stays at 100 degC.
Question 4 of 14
Two beakers hold equal water; one is wide and shallow, the other tall and narrow, both in the same room. The wide one evaporates faster because of greater:
humidity
temperature
surface area
wind speed
Explanation: More exposed surface area lets more surface particles escape per second.
Question 5 of 14
Assertion: Evaporation causes cooling. Reason: The slowest particles escape from the surface. Choose the correct option.
Both true, reason explains assertion
Assertion true, reason false
Assertion false, reason true
Both false
Explanation: Evaporation does cool, but it is the FASTEST (most energetic) particles that escape, so the reason is false.
Question 6 of 14
Dry ice (solid CO2) is preferred over ordinary ice for storing ice-cream mainly because it:
is colder and sublimes leaving no liquid
is cheaper
melts faster
is heavier
Explanation: Dry ice sublimes directly to gas, leaving no wet residue, and is very cold.
Question 7 of 14
On a hot, humid day a desert cooler works poorly because high humidity:
raises the boiling point
reduces the rate of evaporation
increases wind speed
lowers the temperature
Explanation: A cooler relies on evaporation, which slows when the air is already near saturation.
Question 8 of 14
If 1 kg of ice at 0°C and 1 kg of water at 0°C are compared, the ice has:
more energy
less energy by the latent heat of fusion
the same energy
no energy
Explanation: Water at 0 degC has already absorbed the latent heat of fusion that the ice has not, so ice has less energy.
Question 9 of 14
A liquid X evaporates faster than liquid Y at the same temperature. This suggests X has:
stronger forces between particles
weaker forces between particles
larger particles only
higher boiling point
Explanation: Weaker inter-particle forces let particles escape more easily, so X is more volatile.
Question 10 of 14
Why is dilute, not concentrated, evidence used: a wet earthen pot cools water but a glazed (sealed) pot does not. The reason is the glazed pot has:
thicker walls
no pores for water to evaporate through
more colour
higher density
Explanation: Cooling needs water to seep out and evaporate; a sealed glazed surface has no pores, so no evaporation.
Question 11 of 14
When a gas is cooled and compressed strongly, it can turn into a liquid because:
particles gain energy
particles come closer and attraction increases
spaces increase
temperature rises
Explanation: Cooling lowers energy and pressure forces particles together, increasing attraction until liquefaction.
Question 12 of 14
A patient with high fever is given a sponge bath because evaporation of water from the skin:
raises body temperature
absorbs heat from the body and cools it
adds latent heat to the body
increases humidity inside
Explanation: Evaporating water draws latent heat from the body, helping to bring the temperature down.
Question 13 of 14
The correct increasing order of kinetic energy of particles is:
gas < liquid < solid
solid < liquid < gas
liquid < solid < gas
gas < solid < liquid
Explanation: Particles move fastest in gases and slowest in solids, so kinetic energy: solid < liquid < gas.
Question 14 of 14
Naphthalene balls slowly disappear over weeks without leaving any liquid. This is because of:
melting
evaporation only
sublimation
condensation
Explanation: Naphthalene changes directly from solid to vapour (sublimation), leaving no liquid behind.