Answer: Option A. ->
:

Each part: 1 Mark
(i) The normal body temperature of a human is 37${}^{\circ }$C.

(ii) It cannot reach us by conduction or convection as there is no medium in space between the earth and the sun. From the sun the heat comes to us by radiation.
 

Answer: Option A. ->
:
Each option: 1 Mark
(a) The general mode of heat transfer in solids is conduction.
(b) The general mode of heat transfer in liquids and gases is convection.

Answer: Option A. ->
:
(a) Reason: 1 Mark
(b) Working: 2 Marks
(a) Hot air rises up because, it has lesser density than the cooler air around it.
(b) A hot-air balloon works on the principle that hot air rises up.
It consists of a burner and a balloon envelope. When the burner is lit, it heats the air around it.
The hot air rises up and the cold air on the sides comes near the burner. The same process continues for a long time.
The hot air gets trapped in the balloon and the hot air balloon rises, depending on the amount of hot air in it..
 

Answer: Option A. ->
:
Modes: 1 Mark each
The various ways in which heat is transferred are:
(i) Conduction: In this mode, heat is transferred between adjacent molecules through vibration, without the actual movement of the molecules. This type of heat transfer happens in metals.
(ii) Convection: In air and water, heat is transferred by convection. The hot air becomes lighter and moves upward which is then replaced with the colder particles from the top and sides. In convection, the actual movement of molecules takes place.
(iii) Radiation: This mode of heat transfer doesn't require any medium for its transfer. All hot bodies radiate heat. When heat falls on an object, a part of it is absorbed, a part of it is reflected and a part of it is transmitted. The temperature of the body rises due to the absorbed part of the heat.

Answer: Option A. ->
:
Insulator with examples: 1.5 Marks
Conductor with examples: 1.5 Marks
Substances which allows heat to pass through them easily are called conductors. For example aluminum, copper and iron.
Insulators are poor conductors of heat. Insulators do not allow heat to pass through them easily. For example wool, wood, and plastic.
 

Answer: Option A. ->
:

Part (a) : 3 Marks
Part (b) : 2 Marks
(a) The various precautions to be taken while reading a clinical thermometer are:

• The thermometer should be washed before and after the use, preferably with an antiseptic solution.


• Ensure that the mercury level is below 35${}^{\circ }$ C.


• Read the thermometer keeping the level of the mercury along the line of sight.


• Do not hold the thermometer bulb while reading.


• Handle the thermometer with care, if it hits a hard object it will break.

(b) 
$\begin{array}{cc}\left(i\right)Landbreezeblowsduring& \left(d\right)night\\ \left(ii\right)Seabreezeblowsduring& \left(c\right)day\\ \left(iii\right)Darkclothesarepreferredduring& \left(b\right)winter\\ \left(iv\right)Lightcolouredclothesarepreferredduring& \left(a\right)summer\end{array}$

Answer: Option A. ->
:

(i) Heat : 2 Marks
(ii) How is it measured : 1 Mark
(iii) Explanation : 2 Marks
(i) Heat is a form of energy which flows from a hot body to a cold body.
(ii) A thermometer is used to measure the temperature of a substance.
(iii) In solids, generally, the heat is transferred by the process of conduction because particles of solids are closely packed and heat is transferred from the hotter end to the colder end of an object.

Answer: Option A. ->
:

(a) Land and Sea breeze: 2 Marks
     Radiation: 2 Marks
(b) Explanation: 1 Mark
(a) Water takes a bit more time to warm up and is able to retain the heat longer than land does. In the day, when the sun is up, the land heats up very quickly and the air above it warms up a lot more than the air over the water. The warm air over the land is less dense and begins to rise. Low pressure is created. The air pressure over the water is higher with cold dense air, which moves to occupy the space created over the land. The cool air that comes along is called a sea breeze.
In the night, the reverse happens. The land quickly loses its heat whiles the water retains its warmth. This means the air over the water is warmer,  air is less dense and begins to rise. Low pressure is created over the water. Cold and dense air over the land begins to move to the water surface to replace the warmer rising air. The cool breeze from the land is called a land breeze.
Convection is the process responsible for land and sea breeze. Convection is the process of transfer of heat from one place to another by the actual movement of the particles. Particles carry heat from one place to another. 

Radiation is the process in which heat flows from one object to another object either through the medium or through vacuum. In convection, a medium is necessary for heat transfer from one end to another but in radiation, no medium is required for transferring of heat.
(b) Sun warms the earth by the process of radiation.

Answer: Option A. -> True
:
A

A body is defined as hot or cold with respect to some reference. Hotness of a body is generally stated with reference to another body or the surrounding.

Answer: Option C. -> either mercury based or digital
:
C

Clinical thermometers are small medical thermometers used for measuring a person's temperature. Mercury-based clinical thermometers have been considered the most accurate liquid-filled thermometer type. However, Mercury is a poisonous metal. Therefore a safer and an accurate alternative option, is to use digital clinical thermometers. Thus, both mercury and digital clinical thermometers are used.