Matter In Our Surroundings - MCQ Test (22-11-2017) - Class 9 MCQ

The boiling point of pure water is 100^oC or 373 K (100^oC = 273 + 100 = 373 K). Boiling is a bulk phenomenon. At this temperature, particles from the bulk of the liquid gain enough energy to change into the vapour state. Therefore, the physical state of water at 100^oC is water vapour (gaseous state of matter).

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.

Cooling is not caused during boiling. The normal room temperature is 298K or.25^∘C Evaporation is a surface phenomenon but boiling is a bulk phenomenon. The liquid having low boiling points evaporate faster.

Evaporation causes cooling effect because the heat of evaporation is absorbed by the surroundings. Evaporation of acetone present in nail polish remover absorbs the latent heat from the nail Causing cooling of a  nail.

Kelvin is the SI unit of temperature. To change a temperature on the Kelvin scale to the Celsius scale, 273 has to be subtracted from the given temperature. To convert a temperature on the Celsius scale to the Kelvin scale, 273 has to be added to the given temperature. 

Temperature on Celsius scale = Temperature on Kelvin scale - 273

∴^∘C = K−273 = 27^∘C

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

The constant temperature at which solid start changing into liquid at atmospheric temperature is called melting point. At this temperature, both the solid and liquid exist together.

The rate of evaporation increases with increase in temperature, surface area & wind speed but decrease by the increase in humidity.

According to ancient philosophers matter consists of five constituents (panchtatva). They are air, earth, fire, sky and water.

Solids substances have the strongest inter-particle force of attraction. In the given substances, sodium bromide is solid, ethyl alcohol is liquid and ammonia and carbon dioxide are gases. So, the particles of Sodium bromide have the strongest force of attraction.

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

The particles of gases are away from each other. So, gas has the minimum inter-particle force of attraction.Solids have maximum force of attraction

When the pressure on the surface of a gas is increased. The particles of gases comes closer that increase the inter-particle force of attraction.

Desert cooler causes cooling effect due to evaporation of water as evaporation causes cooling effect. A desert cooler works more effectively when weather is hot and dry.

Air is a mixture of gases. Two main constituents of air is  Nitrogen (78%) and Oxygen (21%). Other gases include carbon dioxide, helium, water vapour etc.

Ether and Acetone is most volatile. Alcohol is moderately volatile and water is least volatile. So, the statement, Acetone is least volatile is incorrect statement.

A substance is said to be in liquid state if under normal pressure its melting point is below the room temperature. Melting point of solid and the freezing point of liquid is same. So, statement A is correct but B is wrong.

By touching the surface of china dish. This is due to the fact that to change from liquid to the vapour state, alcohol requires latent heat of vaporisation. the alcohol takes this heat of vaporisation from china dish. The china dish loses heat and gets cooled.

The cloth soaked in water takes longer time in drying as it is less volatile. Cloth soaked in alcohol is will take less time than water and cloth soaked in ether will dry quickly as it is highly volatile. So, correct order is Water < Alcohol < Ether.

Kelvin scale is used as standard unit of temperature. CO₂ is heavier gas than N₂ and O₂.

Gases have maximum fluidity and least rigidity. The particle of solids have negligible kinetic energy. Inter-particle attraction depends on the physical state of the matter. Potassium permanganate is purple in colour.

Evaporation of ether occurs due to absorption of heat by surrounding. So, it is an endothermic process.The chemical reaction in which heat is absorbed in called as an endothermic reaction. The reaction in which heat is evolved is called exothermic reaction and the reaction in which no thermal changes occur is called athermic process.

Sulphur dioxide gas is collected in the lab in a gas jar by upward displacement of the air because Sulphur dioxide gas is heavier than air. The gases lighter than air are collected by downward displacement of water.

K =^∘C+273, 25^∘C = 273+25=298K. So, temperature of 25°Cis equal to 298K.

Anything that occupies space and have mass is called matter. Inter-particle space is maximum in the gaseous state of substance. The particles constitute zig-zag path and solid is most compact state of substance. Matter is not always continuous in nature.

Naphthalene, camphor, iodine and ammonium chloride are sublime substance. So, statement B is correct. Petrol, ether, acetone and carbon tetrachloride are volatile liquid but water is not a volatile liquid.

Statement A is correct. The temperature of the liquid becomes constant once it starts boiling. The heat is used to change the state of matter.

The pressure of air at the sea level is 760 mm (76 cm) of Hg (mercury).

Water can undergo a change in state upon heating and cooling. On heating above 100°C water change into a gaseous state and on cooling below 0°C it changes into the solid state.

The process of changing solids into gases without changing into liquid state or gases directly into solid is called sublimation.