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.

Increase in temperature of water will increase the evaporation of water. It is because, on increasing the temperature, kinetic energy of water molecules increases and more particles get enough kinetic energy to go into the vapour state. This increases the rate of evaporation. Evaporation is the surface phenomenon so it depends upon the exposed surface area. Higher the exposed surface area of water, higher will be the evaporation. When common salt is added to water then surface is occupied by the solvent as well as non-volatile solute particles. So, the escaping tendency of solvent particles decreases and thus the evaporation of water decreases. Therefore, other options [B], [C] and [D] will be decrease the evaporation of water.

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).

Conversion of solid into vapours on heating or vapours into solid on cooling without undergoing in liquid state is called sublimation. The conversion of liquid into gas or vapour is called vaporization. The conversion of liquid into solid is called freezing. The conversion of solid into liquid is called melting.

Therefore, the correct sequence of temperature will be 298 K, 311 K, and 339 K. On converting 25 degree Celsius, 38 degree Celsius, and 66 degree Celsius, to Kelvin scale, we get the following temperatures: 25 + 273 = 298 K, 38 + 273 = 311 K, 66+ 273 = 339 K. Therefore, the correct sequence of temperature will be 298 K, 311 K and 339 K.

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].

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.

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 rate of evaporation increases on increasing the surface area of the liquid.

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].

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

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