Class 9 Science Chapter 1 MCQ

Option C is correct because Hydrogen gas leaking from the container leaves some vacant space inside the container. So, hydrogen gas molecules inside the container occupy all the space available and the distance between the molecules of hydrogen gas will be increased. On increasing the volume of the container of hydrogen gas, more space will be available inside the container and hydrogen gas molecule will occupy all the space available and hence distance between the molecules will be increased. On increasing pressure, hydrogen molecules will come closer and the distance between them will be decreased. More hydrogen gas molecules are available in less volume, so the distance between them will be decreased.

The bromine vapor is heavier than air. And rest of all statement are correct. Hence, your answer will be option [D].

Explanation: The particles of matter attract each other. There are the characteristics of particles of matter.

The correct order of boiling points of diethyl ether, acetone and n-butyl alcohol in kelvin scale is 308 K, 329 K and 391 K, which can be explained as: Boiling point of diethyl ether = 35 degree Celsius + 273 = 308 K Boiling point of acetone = 56 degree Celsius + 273 = 329 K Boiling point of n-butyl alcohol = 118 degree Celsius + 273 = 391 K

When a few crystals of copper sulphate are placed at the bottom of a beaker containing water, then water in the whole beaker turns blue slowly.

At 0°C, water releases some heat to lower the speed of molecules, and when it is cool enough the molecules of water are fixed at one position and they start vibrating. Ultimately, the water molecules convert into ice (solid).

Here, all the statements are correct. Hence, your answer will be option [D].

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.

Here, all the statements are correct. Hence, your answer will be option [D].

The correct order of increasing “force of attraction” between their particles is : Oxygen < Water < Sugar It is because the force of attraction increases in the order i.e. Gas < Liquid < Solid.

Plasma is a fourth state of matter and plasma is a mixture of free electrons and ions. Plasma occurs naturally in the stars including the sun.

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.

Here, all the statements are correct. Hence, your answer will be option [D].

Ammonia gas can be liquefied by applying high pressure and lowering the temperature. In option [B]: Solid carbon dioxide is stored under high pressure. In option [C]: The conversion of solid carbon dioxide into carbon dioxide gas is a change of state which is caused by the decrease in pressure and increase atmospheric temperature. In option [D]: Whatever be the temperature at which evaporation take place, the latent heat of vaporization must be supplied whenever a liquid change into vapour or gas.

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.

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.

Here, all the statements are correct. Hence, your answer will be option [D].

Low temperature and high pressure required to liquefy gases to liquids. There is a lot of space between the particles of a gas. On applying high pressure, the particles of gas move get so close that they start attracting each other sufficiently forming a liquid. When gas is compressed too much, heat is produced, so it is necessary to cool it. Cooling lowers the temperature of compressed gas and helps in liquifying it. Hence, a gas can be liquefied by applying high pressure and lowering the temperature (cooling).

The process of changing a gas or vapour to a liquid by cooling is called condensation.

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

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

Here, all these statements are correct. Hence, your answer will be option [D].

Here, all these statements are correct. Hence, your answer will be option [D].

The smell of perfume spreads due to the diffusion of perfume into air.

Once the water has begun to boil, the temperature remains constant at hundred degree Celsius until all the water has changed into steam.