1) What is clinical thermometer?

 The most common thermometer used almost in every house is clinical thermometer. We use it to measure the temperature of human body, when some one has fever. The normal temperature of body in clinical thermometer is 37^oc to 98.4^of

2) What is the limitation of clinical thermometer?

We cannot use clinical thermometer for measuring the temperature of any object more than 42^oc(more than body temperature). It may  break when  kept  in the sun or near a flame.

3) What is maximum and minimum thermometer?

A thermometer used to measure the maximum and minimum temperature of previous day is called Maximum – Minimum thermometer. It is used by the weather department to report / predict the weather.

4) What is laboratory thermometer?

 The thermometer which is used to measure the temperature of other objects in laboratory is called laboratory thermometer. The range is – 10^oc to 110^oc. It also contain a thread of mercury.

5) What are the precaution needed while reading a laboratory thermometer?

        (i) The thermometer should be kept upright not tilted.
        (ii) Bulb should be surrounded from all the substance of which the temperature is to be measured.
        (iii) The bulb should not touch the surface of the container.

6) Why do we use mercury in the thermometer in place of water?

        (i) Mercury expands more than water
       (ii) Mercury do not stick on the walls of the thermometer like water.
       (iii) Mercury can be easily collected when thermometer breaks.
       (iv) It shines more than water and be seen easily in the thin glass tobe of the thermometer.

7) State similarities and differences between the laboratory thermometer and the clinical thermometer.

  Similarities between the laboratory thermometer and clinical thermometer
(i) Both are used to note the temperature.
(ii) Both are made of long narrow uniform glass to be with a bulb at one end.
(iii) Mercury is used in both thermometers
(iv) Both are marked in Celsius scale

Difference between the laboratory thermometer and clinical thermometer.

(i) Laboratory thermometers are larger and broader in size as compared to clinical thermometer.
(ii) Laboratory thermometer are used to note the temperature of different objects in different states while clinical thermometers are used only to note the temperature of human beings.
(iii) Laboratory thermometers are marked from -10^oc to 110^oc while clinical ones are marked between 35^oc to 42^oc only
(iv) While noting readings of thermometer laboratory thermometers has to be in touch with the object whose temperature is to be noted but in clinical temperature it is seen when outside the body.
(v) There is no kink in the laboratory thermometer but there is one kink in clinical thermometer to prevent mercury level from falling on its own.

8) In places of hot climate, it is advised that the outer walls of houses be painted white. Explain.

  Light coloured or shiny surface reflects most of heat that falls on  them with the result, that  the surface remains cool. So, it is advised to paint outer walls of houses white in places of hot climate.

9) When cold milk is added to hot tea, how does the heat transfer take place?

 When cold milk is added to hot tea, the two come in contact with each other. The transfer of heat energy takes place from hot molecules to cold molecules by the process called conduction.

10) What are the main conditions necessary for the flow of heat?

          Condition for the flow of heat. These are following three conditions for the flow of heat from one to another.

1.  The two substances should be in contact with each other
2. The temperature of both the substances should be different.
3. The heat flows from hot to cooler substances.

11) If a spoon is held over fire, it becomes hot after sometime. Describe the process of heating up.

 We know that in a solid the molecules are packed close together. When one end of the spoon is held over the fire, the molecules of material of spoon absorb the heat energy and begin to vibrate rapidly. These molecules, in turn, cause their neighboring molecules to vibrate. This process continues along the length of the spoon and energy is transferred from the hotter part to the colder part. After sometime, the other end of the spoon also becomes hot.

12) Why is it preferred to wear light clothes in summer and dark clothes in winter?

Dark coloured clothes are good absorbers of heat as compared to white clothes. The dark coloured clothes absorb the heat falling on them and become warmer. So we feel warm in winter by wearing these clothes. On the other hand, white clothes reflect heat coming from the sun. That is why, we prefer to wear bright clothes in summer and dark clothes in winter.

13) Define conduction. Why the handles of cooking utensils are made of insulators?

The mode of transfer of heat in which the heat is transferred from one particle to another without the actual motion of the particles is called conduction. The handles of cooking utensils are made up of insulating materials because they do not allow heat to flow through them. So heat cannot reach our body and thus our hand is prevented from burning.

14) Distinguish between heat and temperature

15) What is convection? Give two practical applications of convection of heat.

 The process of transference of heat in which a gas or a liquid on being heated circulates from one place to another is called convection. All the liquids and gases are heated by the method of convection.

Examples

    (i) When a stove is the air in contact with the hot stove becomes warm. On being heated, it expands and becomes lighter. As a result, it rises upwards and the cool air from its surrounding comes to take its place.
   (ii) The ventilation of ordinary buildings is due to convection.

16) Define Radiation.

 The process of  transferring   heat from one body to another without heating the intervening medium is called radiation. No medium is needed for the transference of heat by this process.

17) As soon as the test tube is removed from the source of heat, the level of liquid drops. How is this avoided in the thermometer that doctors use?

 It is seen that the level of liquid falls in a test-tube when it is removed from the source of heat. But when the doctor’s thermometer is removed from the source of heat, the level of mercury does not fall. It is because a kink is provided in the tube of the thermometer which prevents mercury from falling down to it own weight.

18) What are the effects of heat?

Heat energy can cause many changes in an object. On heating objects become hotter, they may expand. Heat may change the state of the body. For example, ice changes into water. Heat can also increase the speed of chemical reactions. Heat even kills harmful bacteria. That is why boiled water is generally given to a patient suffering from water-borne disease.

19) Explain the sea breeze and land breeze.

At sea-shore during the day cold air from the sea mores towards the beach. Because the land gets more heated than the sea water. Hot air above the land rises up, and air from the moves towards the land beach. This is called sea breeze.
During the night cold air from the land moves towards the sea. Because the land cools more quickly than the sea water. So hot air above the sea rises up and cold air from the land moves towards the sea. This is called land breeze.

20) Discuss why wearing more layers of clothing during winter keeps us warm than wearing just one thick piece of clothing.

Different layers of clothing traps air inside them. Air is a poor conductor of heat so it prevents the flow of heat from air body to the cold surrounding and makes a body feel warmth.