Heat

The similarities between the laboratory thermometer and clinical thermometer are as follows:

(i) Mercury is used in laboratory thermometer as well as in clinical thermometer.

(ii) Both the thermometer consists of a long, narrow tube of glass.

The differences between the laboratory thermometer as well as clinical temperature are as follows:

(i) The least count of both the temperature differs.

(ii) The range of the temperature used in a laboratory thermometer is high from -10⁰C to 110⁰C whereas, in case of the clinical thermometer, the range is 35⁰ to 42⁰.

(iii) Clinical thermometer is used to measure body temperature however laboratory thermometer is not used for the purpose of measuring body temperature.

a. She dipped the thermometer in a liquid before use. This is done to avoid infection because the liquid in which the thermometer is dipped is an antiseptic and helps in preventing infection.

b. The thermometer is kept under the tongue because below the tongue, the body temperature is more accurate and thus helps in recording the actual body temperature.

c. the body temperature can be measured by keeping the thermometer at some place other than the mouth but the temperature placed at other parts will not be so reliable and accurate because temperature of body parts is different with different body parts.

d. The temperature of different parts is not same and it varies with different body parts.

The normal temperature of domestic animals and birds are recorded as follows:

The normal temperature of Goat varies from 37⁰ - 40⁰C.

The normal temperature of a dog is about 38.3⁰C

The normal temperature of a pigeon (bird) is 40⁰C.

The normal temperature of a cat is 38⁰C

Conductors are the materials which can allow heat to pass through them whereas insulators doesn’t allow heat to pass through them. The examples of conductors are: Aluminum, Iron and Copper. The examples of insulators are wood and plastic.

The paper will not be burnt while rotating the iron rod continuously because iron being a good conductor of heat, allow heat to pass through them. As a result heat is taken away from the paper and the paper doesn’t burn.

a. The hotness of an object is determined by its temperature.

The more is the Temperature of object, the more it will be hot and lesser the temperature of object, lesser will be hotness.

b. Temperature of boiling water cannot be measured by clinical temperature.

Because the range of clinical temperature (35⁰C to 42⁰C) is less and the temperature of boiling water is high. So, it can’ t be measured using clinical temperature.

c. Temperature is measured in unit Celsius.

The temperature is measured with the help of Celsius scale and the symbol is indicated by ⁰C.

d. No medium is required for transfer of heat by the process of Radiation. There is no requirement of any medium to transfer heat in case of radiation.

e. A cold steel spoon is dipped in a cup of hot milk. It transfers heat to its other end by the process of conduction

Because cold steel spoon is a body of low temperature and hot milk acts as a body of high temperature. So, there is a transfer of heat from hot milk to cold steel spoon and this process is known as conduction.

f. Clothes of dark colors absorb heat better than clothes of light colors. This is because dark color absorbs more heat than light colored objects as light colored objects reflects most of the heat that falls on them.

The correct match is : i (d)

Land breeze blows during night because at night the water cools down more slowly than the land, so the cool air moves towards the sea from land and is known as land breeze.

The correct match is : ii. (c)

Sea breeze blows during day because during the day the land gets heated faster than the water. The air over the land becomes hotter and then moves up. The cooler air from sea rushes in towards the land to take its place. The warm air from the land moves to sea to complete the cycle. This is known as Sea Breeze.

The correct match is: iii. (b)

Dark colored clothes are preferred during winter because dark colored objects absorbs radiations better than light colored clothes and help in keeping the body warm during winter.

The correct match is: iv. (a)

Light colored clothes are preferred during summer because they reflect most of the radiation falling on the body and thus light colored clothes are preferred in summers.

When the spiral paper is suspended at flame, then the paper spiral will keep moving because due to convection process, there will be transfer of heat and the air present above the flame will move up which results in movement of paper spiral.

When the card will be removed, then due to diffusion process there will be movement of colored hot water in upward direction and cold water in downward direction. It happened because hot fluid i.e. hot water is lighter than the cold water.

Wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing because air gets trapped in between the layers of the clothes and air, being a bad conductor of heat, doesn’t allow heat to pass through them and heat is retained within the layers keeping the clothes warm.

Since there is no requirement of any medium for transfer of heat in radiation and in conduction, there is transfer of heat between the solids and in case of liquids and gases, heat is transferred by the process of convection. The transfer of heat by different processes can be shown by the diagram as follows:

In places of hot climate, it is advised that the outer walls of houses be painted white because white is a light color and more heat is reflected from the surface and there is less absorption of heat by the walls. It helps in keeping the house cool.

One litre of water at 30^°C is mixed with one litre of water at 50^°C. The temperature of the mixture will be between 30^°C and 50^°C. This is because there is transferred of heat from an object with high temperature to an object having a low temperature. So, heat will flow from one litre of water at 50°C to one litre of water at 30^°C. So, the temperature of the mixture will be between 30^°C and 50^°C.

An iron ball at 40⁰C is dropped in a mug containing water at 40⁰C. The heat will not flow from iron ball to water or from water to iron ball because both the objects are at same temperature and there will be no transfer of heat.

A wooden spoon is dipped in a cup of ice-cream. Its other end

does not become cold because wood is a bad conductor of heat and doesn’t allow heat to pass through them and is therefore, the other end of wooden spoon will not become cold because there will be no transfer of heat.

Stainless steel pans are usually provided with copper bottoms. The reason for this could be that copper is a good conductor of heat and allow to pass heat through them and is therefore can easily be heated.