Heat and Thermodynamics (Physics) Part-II

A glass bottle containing water breaks when kept in a freezer because the frozen water will have more volume than the liquid water. So increased volume will put pressure on the walls of the bottle and it will break.

We know that the mass of liquid displaced by the floating ice equals to the mass of the object. That's why the ice caps float on water. Similarly, when an ice cube melts in a glass of water, the water level does not change as the melted water will occupy exactly the same amount of space as the ice under the water level previously occupied

When you have cloudy night, the clouds prevent heat from escaping through the atmosphere and into space. The clouds act like a blanket and trap the heat. That is why every time when there is a cloudy night, it is always warmer than a clear night.

The cloudy nights are warmer than clear nights because the clouds prevent radiation of heat from the ground and the air and they reflect back the heat.

Whether a given cloud will heat or cool the surface depends on several factors, including the cloud's altitude, its size, and the make-up of the particles that form the cloud. Low, thick clouds primarily reflect solar radiation and cool the surface of the Earth.

While high, thin clouds primarily transmit incoming solar radiation; at the same time, they trap some of the outgoing infrared radiation emitted by the Earth and radiate it back downward, thereby warming the surface of the Earth. Hence, both of the given statements are incorrect.

The specific heat capacity is the property of the substance which determines the change in the temperature of the substance (undergoing no phase change) when a given quantity of heat is absorbed (or rejected) by it.

It is defined as the amount of heat per unit mass absorbed or rejected by the substance to change its temperature by one unit. Water has the highest specific heat capacity compared to other substances.

The specific heat of water is much greater than that of land surface. Owing to its high specific heat capacity, the water of ocean warms up much more slowly than the land during summer and consequently wind from the sea has a cooling effect.

On the other hand, the ocean slowly cools in winter, keeping the air warm. That is the reason why the temperature contrast between continents and oceans is greater during summer than in winter.

Hence, both Statement-I and Statement-II are correct and Statement-II is the correct explanation for Statement-I.

It is well known that even after harvesting of the fruits the process of respiration continues and brings about ripening, change in colour, softening of flesh, increase in sugar content and development of flavour.

These changes occur more rapidly at higher temperature. This means that the lower the temperature of storage the longer would be the storage life of the fruit. In cold chambers the rate of respiration of fruits is decreased

Woollen clothes keep us warm in winter. It is just because woollen clothes have fibres and between those fibres, air is trapped which reduces heat loss. Air reduces heat loss because it is an insulator or poor conductor of heat. Thus statement (A) is correct but reason (R) is false.

Humidity is the percentage of water vapour present in air. As the humidity increases, the percentage of water vapour in air increase and this decreases the density of air.

This results in the increase of velocity of sound. So increase in the humidity of air increases the velocity of sound in air. Thus, statement (c) is not correct.

If the door of a refrigerator kept open in a room, the temperature will start to rise inside the refrigerator. The thermostat will kick in and try to cool it back down. This means the motor is running, which means heat is being added to the room resulting warmer room.