Science M.C.Q-[Che-1M]

1. A-gas, B-sold and C-liquid.

1. Cotton absorbs water

Explanation:

Cotton absorbs water, and thus, causes sweating. Sweat comes out the clothing and in contact with the atmosphere.

It evaporates taking up the heat from the surrounding and thus, gives a cooling effect.

1. Atmospheric pressure is low at higher altitudes.

Explanation:

Have a friend put their hands on your shoulder and push down. Now try to jump upwards.

It's difficult to do so right?

You would need more energy to jump higher correct?

The same applies to molecules of water.

The air pressure exerts a force on them which they must overcome in order to boil.

The greater the air pressure the greater the temperature at which the water will boil.

1. The sweat particles absorb heat from the body and get converted into vapour, thereby reducing its temperature

Explanation:

It happens due to evaporative cooling.

The sweat gets vaporized from the skin into the atmosphere, by absorbing heat from the body.

Thus the body cools down as it loses heat.

3. Spirit evaporates quickly.

Explanation: 

Spirits are very volatile liquids, which means they evaporate very quickly. When we apply spirit on our body, its particles gain energy from the surface and evaporate, thus, giving our body a cool sensation.

1. Evaporation increases with increase in wind speed.

4. Both A and C.

Explanation:

Evaporation is a surface phenomenon. If the surface area is increased, the rate of evaporation increases.

While putting clothes for drying up, we spread them out, because, more area is exposed to sun and wind which speeds up the rate of evaporation.

2. Tiny particles of sugar adjust among the space between tiny particles of water

2. Increase in humidity

Exaplantion:

The various factors that increase the rate of evaporation of water are:

Increase in temperature

Increase in exposed surface area

Increase in wind speed

So, from the given options, increase in temperature, surface area and wind speed will increase the rate of evaporation.

Humidity does not.

Humidity refers to the amount of moisture or water vapour in the air.

If the humidity is high and the surrounding air is already saturated with water vapour, air's moisture intake will reduce.

Consequently, the rate of evaporation reduces.

2. Evaporation takes place within the liquid not on the surface.

Exaplantion:

Evaporation is a type of vaporization which occurs on the surface of the liquid.

The evaporation process can occur at a temperature below the boiling point.

So by evaporation, only the liquid molecules on the surface get converted to water vapour.

2. The molecules in a liquid are arranged in a regular pattern.

Explanation:

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

3. Gases and liquids behave as fluids.

Explanation:

Gases and liquids behave as fluids because fluids are the substances that have the ability to flow. Gases and liquids can flow easily because their particles are free to move.

3. Evaporation, diffusion, expansion of gases.

Explanation:

Evaporation, diffusion and expansion of gases increase on raising the temperature.Evaporation rate increases because on increasing temperature, kinetic energy of molecules increases, so the molecules present at the surface of the liquid leave the surface quickly and go into the vapour state. Diffusion and expansion of gases also increase as the molecules move more rapidly and try to occupy more space.

3. Evaporation, diffusion, expansion of gases.

Explanation:

The rates of evaporation, diffusion and expansion of gases increases due to increase in temperature because when temperature increases the kinetic energy of molecules increases, which breaks or weakens the interaction between the atoms and sets the molecules free.

3. Depth of the liquid

Exaplantion:

Substance or liquid that has a larger surface area will evaporate faster as there are more surface molecules per unit of volume that are potentially able to escape.

The higher the temperature of substance or liquid, the greater is the kinetic energy of the molecules at its surface, and therefore the faster the rate of evaporation.

If the air is saturated with a great amount of water causing high humidity, it causes low capacity for the evaporating substance.

2. All forms of matter have colour.

Explanation:

Some forms of matter like air, pure water, etc., are colourless.

While all forms of matter have volume, mass and can be living or non-living.

2. Evaporation of liquid takes place only at its boiling point.

Explanation:

During evaporation, water does not convert into a gas or steam, but the random movement of molecules on the surface of the water provides some of the molecules with enough energy to escape from the surface into the air.

4. All are correct

Explanation:

In gaseous phase particles are present at a maximum distance or loosely apart from each other while solid has tightly packed particles in compact form.

Particles follow a specific motion (zig-zag path) called as Brownian motion.

3. The particles of some of the matter are moving constantly.

Explanation:

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.

1. Sponge is compressible, but considered as a solid.

_Explanation:

Yes, sponge is a solid. Although sponge has small pores which traps air however it releases the same when the sponge is pressed and by this we are able to compress it. This helps the sponge to regain its shape and mass.

3. Low temperature, high pressure.

Explanation:

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.

4. All of these.

4. Its rate decreases with decrease in humidity.

Explanation:

Temperature: The rate of evaporation increases with an increase in temperature.

Surface area: The rate of evaporation increases with an increase in surface area.

Humidity: The amount of water vapour present in the air is called humidity. The rate of evaporation decreases with an increase in humidity.

Wind speed: Evaporation increases with an increase in wind speed.

3. The particles of matter are in stationary state.

2. Evaporation

Explanation:

Boiling is a bulk phenomenon because all molecules gain energy on heating.

Evaporation is a surface phenomenon as the molecules of the surface gets sufficient energy to overcome the force of attraction which will help in converting to the vapour phase.

Dilution is also a bulk phenomenon as the volume of solution increases throughout the bulk of the solution.

1. Boiling

Explanation:

In boiling, all particles get energy when they heated.

Evaporation takes place on the surface. it is a surface phenomenon.

Adsorption also takes place on the surface. It is also a surface phenomenon.

3. Temperature

Explanation:

When the temperature of a substance is increased collision, rate between particles increases which increases.

The speed of particles which implies that the kinetic energy of particles is directly proportional to the temperature of the substance.

1. High pressure on liquid surface

2. Latent heat.

Explanation:

Latent heat is absorbed because during change of state because it is the heat energy that has to be supplied to change the state of a substance.

2. Latent heat

1. Dissolution of sugar into water

1. Lce at 0⁰C

Explanation:

Lce is more effective than water in cooling liquids because ice needs additional energy to convert itself to water at zero degree celsius.

Thus it absorbs more heat from the liquid system making the liquid system cooler so ice at 0⁰C is cooler than water at 0⁰C.

1. Increase in temperature of water.

Explanation:

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.

3. Increase in temperature of water

Explanation:

As the temperature of the water increases, the kinetic energy increases

As a result, the force of attraction between the molecules decreases, and the molecules become more and more separated. 

Thus, increasing the temperature of a body of water also often increases evaporation.

This is because as the temperature rises, the water molecules begin moving about more rapidly and will finally escape.

1. The rate of evaporation in a coastal area is less because of high humidity

Explanation:

The rate of evaporation in a coastal area is less because of high humidity.

High humidity represents higher concentration of water vapour in the air due to which temperature of the surrounding atmosphere decreases and the rate of evaporation also decreases.

2. Releases some heat.

Explanation:

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).

3. Remains same

Explanation:

The level of water remains same as the sugar particles gets into the spaces between water molecules therefore the level of water remains same.

2. The particles of salt get into the spaces between particles of water

1. Cools down

Explanation: 

Liquid requires latent heat of vaporization.

So, when the liquid takes up the heat from the surrounding to vaporize, the temperature of surrounding reduces, and it cools down due to loss of heat.

2. Does not increase at all.

Explanation:

During melting, temperature of the ice does not change at all because the heat is used in overcoming the particle-particle attraction forces, which in turn keeps the temperature constant.

4. Does not rise at all.

Explanation:

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.

3. Bromine is heavier than air.

Explanation:

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

3. The particles of bromine are moving but those of air are not moving.

Explanation:

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.

3. Diffusion.

Explanation:

Both water and potassium permanganate are made up of tiny particles. The particles of potassium permanganate are coloured while those of water are colorless. When the crystals of potassium permanganate are kept in water, the purple-coloured crystals of potassium permanganate break further into smaller particles that occupy the space between the molecules of water imparting a purple colour to the water.

3. 298.16K, 318.16K, 77°F, 113°F

1.  Volume of gas decreases with increase in pressure

Exaplantion:

The volume of gas decreases with an increase in pressure.

This leads to the conversion of the gaseous state into a liquid state and eventually into a solid-state.

The volume of the gas decreases by applying pressure on gases because gases are compressible. 

2.  Heat absorbed when a substance changes phase from liquid to gas.

Explanation: 

Latent heat of vaporization is the amount of heat absorbed when 1 kg of liquid changes into vapor at constant temperature.

When a liquid vaporize at the normal boiling point the temperature of the liquid will not rise beyond the temperature of the boiling point. 

1. It evenly spreads in all directions in water

Explanation:

When ink is dropped in water, it evenly spreads in the water due to the principle of diffusion.

This happens because water as well as the ink particles (molecules) are in continuous random motion.

1. Its molecules move faster

Explanation:

Solid-state has the least intermolecular space and most packed structure.

On heating of a solid, the intermolecular forces decrease, space between the molecules increases.

The particles gain energy and there is an increase in kinetic energy and the molecules move faster.

2. Evaporation

Explanation:

The water kept in an earthen pot remains cool even in summer because of evaporation.

Earthen pot has a large number of tiny pores in its walls and some of the water molecules continuously keep seeping through these pores to outside the pot.

This water evaporates continuously and takes the latent heat required for vaporization from the remaining water. In this way, the remaining water loses heat and gets cooled.