Chapter Review:

---

• Temperature is measured by a device called thermometer.
• The thermometer that measures our body temperature is called a clinical thermometer.
• The temperature of normal body is 37 °C.
• The range of clinical thermometer is 37 °C to 42 °C.
• The range of laboratory thermometer is -10°C to 110°C.

• The process by which heat is transferred from the hotter end to the colder end of an object is known as conduction.

• The process of transferring of heat in liquid like water is known as convection. 

• The process of transferring the heat which does not need any medium is known as radiation.

• The materials which allow to pass the heat from themselves easily are  known as conductor of heat. EX:- copper, Iron, almunium etc.

• The materials which does not allow to pass the heat from themselves are known as bad conductor of heat. Ex:- wood, plastics etc.  

• Poor conductors are known as insulators.

• The warm air from the land moves towards the sea to complete the cycle. The air from the sea is called the sea breeze.

• The cool air from the land moves towards the sea. This is called the land breeze.

Exercise 

---

Q1. State similarities and differences between the laboratory thermometer and the clinical thermometer.

Answer:

Similarities:

(i) Both use mercury.

(ii) Both measure temperature.

Differences:

(i) The temperature on laboratory thermometer falls by itself but does not happen in clinical thermometer.

(ii) The range of laboratory thermometer is much higher than clinical thermometer.

Q2. Give two examples each of conductors and insulators of heat.

Answer:

Conducters            Insuiators

(i) Steel               (i) Wood

(ii) Copper             (ii) plastic 

Q3. Fill in the blanks:

(a) The hotness of an object is determined by its __________.

(b) Temperature of boiling water cannot be measured by a _____________ thermometer.

(c) Temperature is measured in degree ______________.

 (d) No medium is required for transfer of heat by the process of __________.

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

(f ) Clothes of ______________ colours absorb heat better than clothes of light colours.

Answer:

(a) temperature (b) clinical (c) celsius (d) radiation (e) conduction (f) black 

Q4. Match the following :

(i) Land breeze blows during                  (a) summer

(ii) Sea breeze blows during                   (b) winter

(iii) Dark coloured clothes are preferred during (c) day

(iv) Light coloured clothes are preferred during (d) night

Answer: 

Column-I	Column-II
(i)Land breeze blows during	(d) night
(ii)sea breeze blows during	(c) day
(iii)Dark coloured clothes are preferred during	(b) Winter
(iv) light coloured clothes are preferred during	(a) summer

Q5. Discuss why wearing more layers of clothing during winter keeps us warmer than wearing just one thick piece of clothing .

Answer:

If there are more than one layer of clothes,air would be trapped in between them.Air is a poor conductor of heat and thus retains heat and makes us feel warmer.  

Q6. Look at Fig. 4.13. Mark where the heat is being transferred by conduction, by convection and by radiation.

Q7. In places of hot climate it is advised that the outer walls of houses be painted white. Explain.

Answer:

Objects with white surface reflect more heat and absorb less.So,less heat from outside would enter the house and it will remain cool.

Q8. One litre of water at 30°C is mixed with one litre of water at 50°C. The temperature of the mixture will be

(a) 80°C    (b) more than 50°C but less than 80°C

(c) 20°C    (d) between 30°C and 50°C 

Answer:

(d) Between 30°C and 50°C

Q9. An iron ball at 40°C is dropped in a mug containing water at 40°C. The heat will

(a) flow from iron ball to water.

(b) not flow from iron ball to water or from water to iron ball.

(c) flow from water to iron ball.

(d) increase the temperature of both.

Answer:

(b) not flow from iron ball to water or from iron ball.

Q10. A wooden spoon is dipped in a cup of ice cream. Its other end (a) becomes cold by the process of conduction.

(b) becomes cold by the process of convection.

(c) becomes cold by the process of radiation.

(d) does not become cold.

Answer:

(d) Does not become cold. 

Q11. Stainless steel pans are usually provided with copper bottoms. The reason for this could be that

(a) copper bottom makes the pan more durable.

(b) such pans appear colourful.

(c) copper is a better conductor of heat than the stainless steel.

(d) copper is easier to clean than the stainless steel.

Answer:

(c) Copper is better conductor of heat than the stainless steel.

Additional questions with solutions: (Notes)

---

Que. – What is thermometer?

Ans. – A device which is used for recording temperature is known as thermometer.

Que. – What is clinical thermometer?

Ans. - A device which is used for recording body temperature is known as clinical thermometer.

Que. – What is the temperature of normal body?

Ans. – 37 °C

Que. – Which thermometer do not use mercury?

Ans. – Digital thermometer.
Que. – What is the range of clinical thermometer?

Ans. – 37 °C to 42 °C.

Que. – What is laboratory thermometer?

Ans. – The temperature of some other things are measured by a special kind of thermometer. Which range is generally –10°C to 110°C is known as laboratory thermometer.

Que. –Why should we use antiseptic solution to wash out the thermometer?

Ans. – After using the thermometer it get infected or may be isolated with germs.  So we use antiseptic solution to wash out the thermometer.

Que. – What is conduction?

Ans. – The process by which heat is transferred from the hotter end to the colder end of an object is known as conduction.

Que. – Why does a metallic pot get heated when we kept it on a flame?

Ans. – Due to conduction.

Que. – How does the sun’s heat reaches to us?

Ans. – The heat of the sun reaches us by radiation.

Que. – What is convection?

Ans. – The process of transferring of heat in liquid like water is known as convection.

Que. – Define conductor of heat? Write with examples.

Ans. – The materials which allow to pass the heat from themselves easily are  known as conductor of heat. EX. – copper, Iron, almunium etc.

Que. – Define bad conductor of heat with examples.

Ans. – the materials which does not allow to pass the heat from themselves are known as bad conductor of heat. Ex – wood, plastics etc.

Que. – What is radiation?

Ans. – The process of transferring the heat which does not need any medium is known as radiation. Ex – reaching the heat of the sun to us.

Que. – What are the modes to transfer the heat?

Ans. – There are three modes

  (i)  Conduction

  (ii) Convection

   (iii) Radiation

Que. – Why does it seem comfortable to put on deep coloured clothes in winter?

Ans. – The deep coloured surface usually absorbs more heat, so putting on deep coloured clothes in winter is comfortable.

Que. – Which colour absorbs more heat?

Ans. – Black.

Que. – Why should we put on the white dress in summer?

Ans. – Light colour or white dress reflects the most of the heat radiation and absorbs less heat so that it keeps us comfortable.

Que. – Why do woolen clothes keep us warm in winter?

Ans. - woolen clothes keep us warm in winter because the wool is bad conductor of heat. The airs trap among its fibers.

Que. – by which mode of transferring of heat will take place in copper?

Ans. – conduction.

Question - Answer:

---

Que: What is a clinical thermometer?

Ans: The thermemeter that is used to measure human body temperature is called a clinical thermometer.

Que2: How is degree celsius denoted?

Ans: ^oC.

Que3: What is the normal temperature of human body?

Ans: the normal temperature of human body is 37^oC.

Que4: what gets hotter soon, land or water?

Ans: Land.

Que5: What caution do you suggest regarding a clinical the thermometer?

Ans: A clinical thermometer should not be used for measuring the temperature of any object other than the human body. Also aoid keeping the thermometer in the sun or near a flame. It may break.

Que6: Why should you wear white clothes in summer and black clothes in winter?

Ans: Dark surface absorb more heat and, therefore, we'feel comfortable withe dark - coloured clothes in the winter. Light coloured clothes reflect most of heat the falls on them and, therefore, we feel more comfortable wearing them in the summer.

Que: Describe the construction of a clinical thermometer.

Ans: A clinical thermometer consists of a long, narrow, uniform glass tube. It has a bulb at one end. This bulb contains mercury. Outside the bulb, a small shining thread of mercury can be seen. There is also a celsius scale on the thermometer.

Que: While Construcating a house in a castal area, in which direction should the window preferbly face and why?

Ans: Window should preferably towards the sea beach so that the sea breeze coming form sea keeps the house cool during the day time.

Que: The mercury does noit fall or rise in a clinical thermometer when taken out of the mouth. Explain why?

Ans: Because of the kink present in the thermometer, the mercury does not fall or rise.

Que: It a pan ias removed from the fire, then why does it cool down?

Ans: When a pan is removed from tghe fire, it loses heat to the surroundings by radiation and its cools down.

Que: Name the mode of transfer of heat in which meadium is not required.

Ans: Radiation is the mode of transfer of heat in which is not required. 

Que: its is preferred to use thin blankets rather than one thick blanket. Explain the reason?

Ans: In case of two thin blanke5ts. there is an air gap which does not allow heat pass out frim the body and its is not as such as in case of one thick blanket.

Que: Why is it adivised not to hold the thermometer by its bulb while reading it?

Ans:  it adivised not to hold the termometer bulb while reading it as the level of mercury increases from the actual reading by our body temperature.

Que: Briefly mention one application of kink in the clical thermometer.

Ans: The clinical thermometer consists of kink which prevents the mercury level from falling on its own.

Que: explain how do we find out how hot an object really is.

Ans: by using thermometer, we can measure the degree of hotness of a body.

Que:How can we measure the temperature of other object rather than human body?

Ans: Temperature of other object is measured with laboratory thermometer because clinical thermometer is not suitable for higher temperture.

Que: How does the heat travel in air?

Ans: heat travels in air through convection.

Que: We are adivsed to use an umbrella when you go out in the sun. comment.

Ans: We use an umbrella to protect us from heat coming from the sun in the from of radiation.

Que: state the limitation of clinical thermomter.

Ans: The clinical thermometer cannot be used for measuring the temperature of any lobject more than 42^o C. If it kept in the sun or near a flame, then this clinical thermometer can be hbreak.

Que: Is the body temperature of every person 37^oC.

Ans: No, the body temperature of every person is not 37^oC. It is an average temperature. It could be slightly higher or slightly lower.

Que: While reading a clinical thermometer, what precautuions should we take?

Ans: Reading a clinical thermometer.

Que: The clinical thermometer is not used to measure high temperature. why?

Ans: Clinical thermometer has the rage 35o C to 42o C. If we use it to measure high temperature, it may braek and mercury present in the clinical thermometer is harmful. so, we cannot use clinical thermometer to measure high temperature.