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

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.

The normal room temperature is 298K or 25^∘C.  Other common values are 293 K (20 C or 68 F). Evaporation is a surface phenomenon but boiling is bulk phenomenon. Liquid having low boiling points evaporate faster. Cooling is not caused during boiling.

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.

Factors Affecting Rate of Evaporation

- Wind Speed: Higher wind speeds can increase the rate of evaporation by removing the saturated air above the liquid surface, allowing more water molecules to evaporate.
- Surface Area: A larger surface area exposed to the air can increase the rate of evaporation as more water molecules are available to escape into the air.
- Temperature: Higher temperatures can increase the rate of evaporation as they provide more energy to the water molecules, allowing them to overcome the intermolecular forces holding them in the liquid phase.

Insoluble heavy impurities do not affect the rate of evaporation as they do not impact the ability of water molecules to escape into the air. These impurities do not alter the physical properties of water that determine its evaporation rate.

Evaporation of water increases with increase in temperature, surface area and wind speed but decrease with increase in humidity. So, larger humidity will decrease the rate of evaporation.

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.

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

Explanation:

• A. It causes cooling: This is correct. Evaporation is a cooling process because it requires heat to change liquid into vapor, which removes heat from the surrounding area.

• B. It increases with increase in humidity: This is incorrect. Evaporation decreases with an increase in humidity because the air is already saturated with moisture, leaving less room for additional water vapor.

• C. It decreases with increase in temperature: This is incorrect. Evaporation increases with an increase in temperature because higher temperatures provide more energy for the liquid molecules to escape into the air as vapor.

• D. It increases with increase in wind speed: This is correct. Wind removes the water vapor from the surface, allowing more liquid to evaporate.

Kelvin scale is used as standard unit of temperature. CO₂ (liquid state) is is stored under high pressure.

- Statement A: Potassium permanganate is actually purple in color, not orange. It is a powerful oxidizing agent commonly used in chemistry experiments.
- Statement B: Gases have maximum fluidity and least rigidity compared to liquids and solids. This is due to the fact that gas particles are far apart and move freely in all directions.
- Statement C: Solids do have a significant kinetic energy of particles, although it is less than that of liquids and gases. The particles in solids vibrate in fixed positions, contributing to their overall kinetic energy.
- Statement D: Inter-particle attraction does depend on the physical state of matter. In solids, the particles are closely packed together, leading to strong intermolecular forces. In liquids, the particles are more spread out, resulting in weaker forces. In gases, the particles are far apart and have very weak intermolecular forces.

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.