Science M.C.Q. [1 M]

An earthen pot has a large number of extremely small pores on its wall. Some of the water continuously keeps seeping through these pores. This water evaporates continuously and takes the latent heat required for vaporization from the earthen pot and the remaining water. In this way, the remaining water loses heat and gets cooled.

Both water and potassium permanganate are made up of tiny particles. The particles of potassium permanganate are coloured while those of water are colorless. When the crystals of potassium permanganate are kept in water, the purple-coloured crystals of potassium permanganate break further into smaller particles that occupy the space between the molecules of water imparting a purple colour to the water.

The transformation of a solid directly into vapour, on heating, is known as sublimation.

With the help of experiments it can be shown that at low temperature and high pressures, gases will liquefy. Because these factors affect the interaction force of molecules i.e. the molecules are able to establish a force of attraction between them on lowering the temperature and increasing pressure.

The rates of evaporation, diffusion and expansion of gases increases due to increase in temperature because when temperature increases the kinetic energy of molecules increases, which breaks or weakens the interaction between the atoms and sets the molecules free.

This value is fixed and is found by performing the experiment in the lab.

Latent heat is absorbed because during change of state because it is the heat energy that has to be supplied to change the state of a substance.

Sodium chloride does not undergo sublimation because it does not show direct change from solid state to liquid state.

Because diffusion is a process in which there is a movement of particles from a region of high concentration to the one with low concentration across the cell membrane.

Temperature of the water during vaporisation does not change at all because the heat is used in overcoming particle-particle attraction forces, which in turn keeps the temperature constant.

Gases and liquids behave as fluids because fluids are the substances that have the ability to flow. Gases and liquids can flow easily because their particles are free to move.

The condition in which hydrogen gas would leak out of the container or if there is an increase in volume of the container in which hydrogen is present, would bring about more distance between the molecules of hydrogen gas.

The above order is correct because the forces of attraction is more in solids compared to liquids and gases. Forces of attraction is least in gases.

Oxygen can be considered to be a fluid because oxygen is a gas and its particles are completely free to move. So, they have the ability to flow.

This value is fixed and is found by performing the experiment in lab.

During melting, temperature of the ice does not change at all because the heat is used in overcoming the particle-particle attraction forces, which in turn keeps the temperature constant.

Both condensation and freezing release heat that lead to decrease in kinetic energy of molecules. When the substance gets cool enough its particles become slower or stop their movement and change their phase into liquid and solid on condensing and freezing respectively.

When surface area increases and temperature rises, evaporation of water increases because the area which is exposed to the outer atmosphere is more and increasing the temperature leads to increase in the kinetic energy, due to which rate of evaporation increases.

The above answer is not true because in liquids the molecules are not arranged in regular pattern. In liquids the molecules are loosely arranged.

The best evidence for the existence and movement of particles in liquids was provided by the Robert Brown. For this experiment, he used pollen grains in water.

The statement that the particles of bromine are moving but those of air are not moving is incorrect because the particles of matter are constantly in motion. It appears as if the air molecules are not moving because air is colourless.

The process occurring here is diffusion and it is unaffected by the mass. Therefore, bromine being heavier, mixes with the colourless air.

Increase in temperature and decrease in pressure are the two factors responsible for the change of solid carbon dioxide into gas.

Liquids have no fixed shape but have a fixed volume. Among the given options, only kerosene is a liquid.

The statement that the particles of some forms of matter move constantly is incorrect because the particles of matter of all three states–solid, liquid and gas are moving constantly. Although the particles of solids are fixed at their positions, they vibrate constantly.