Lakhmir Singh & Manjit Kaur Test: Matter in Our Surrounding - Class 9 Science

At 100°C, water exists in both the liquid state as well as in gaseous state. This is special condition because 100°C is the boiling point of water and as well as liquefaction temperature of the water vapour

An almirah is solid because it is hard and rigid, have fixed shape and have very high density. All these properties are possessed by solid substance only.

Factors Affecting Rate of Evaporation
• Wind Speed: Higher wind speeds can increase the rate of evaporation by carrying away the water vapor molecules from the surface, creating a lower concentration of water vapor around the liquid. This allows more water molecules to evaporate.
• Surface Area: A larger surface area can increase the rate of evaporation as more liquid molecules are exposed to the air, allowing for more evaporation to occur.
• Temperature: Higher temperatures can increase the rate of evaporation as the kinetic energy of the liquid molecules increases, leading to more molecules escaping into the air.
• Insoluble Heavy Impurities: Insoluble heavy impurities do not affect the rate of evaporation. These impurities remain in the liquid and do not impact the evaporation process. The rate of evaporation is primarily influenced by factors such as wind speed, surface area, and temperature.

The correct option is C.
Zero on the Celsius scale (0°C) is the equivalent to 273.15K. 1-degree rise in Celsius scale is equivalent to the 1-degree rise in the Kelvin scale.
 Conversion Formula for the temperature is: C = K−273
300 - 273 =  27° C

Particles of solids have a very high force of attraction, particles of liquid have less force of attraction than solids and particles of gases have very less force of attraction. So the correct order of increasing attraction between particles is Oxygen, water and sugar.

The change of solid directly into vapours is called  Sublimation. The change of liquid state into vapours without coming to it's boiling point is called Evaporation. The latent heat of Vaporization is the heat required to change the state of 1 kg into vapours. Latent heat of fusion is the heat required to Change the state of 1 kg of solid  into liquid.

Gases have no definite shape and volume and are highly incompressible. solid poses rigidity and liquid and gases possess fluidity.

Melting point is defined as the temperature at which a solid turns into a liquid under atmospheric pressure.

In solids, particles are closely packed (very little space between them) and have the least kinetic energy.

In liquids, particles have moderate spacing and intermediate kinetic energy.

In gases, particles are far apart and move very rapidly, having the most kinetic energy.

Answer: B) The spaces between the particles and the kinetic energy are minimum in solids, intermediate in liquids, and maximum in gases.

The correct answer is:

c) Convert 1 kg of a liquid into gas at its boiling point, without changing its temperature

Explanation:

• Latent heat of vaporization is the heat energy required to change 1 kg of a liquid into a gas at its boiling point, without any temperature change.

• This energy is used to overcome the intermolecular forces and convert the liquid into a gaseous state.

Why Not the Other Options?

• a) Describes specific heat capacity, not latent heat.

• b) Refers to latent heat of fusion (solid to liquid).

• d) Incorrect—latent heat does not involve temperature change.

Thus, the correct choice is (c).

Statement A ("Celsius scale is the best scale for measuring temperature") is subjective and incorrect in a scientific context, as the Kelvin scale is the SI unit for temperature and preferred for scientific measurements. Statement B ("CO₂ (liquid state) is stored under high pressure") is true, as liquid CO₂ requires high pressure to remain stable. 
Thus, only statement B is true.

• a) Solids have negligible K.E. of the particles.

  • Correct. In solids, particles vibrate in fixed positions with very low kinetic energy (K.E.).

• b) Gases have maximum fluidity and least rigidity.

  • Correct. Gases flow easily (high fluidity) and have no rigidity.

• c) Potassium permanganate is orange in colour.

  • Incorrect. Potassium permanganate (KMnO₄) is deep purple (violet) in colour, not orange.

• d) Inter-particle attraction depends on the physical state of the matter.

  • Correct. Solids > Liquids > Gases in terms of inter-particle attraction.

The physical state of water at 10^°C is liquid state. Below 0^°C water is in solid state and above 100^°C water is in vapour state.