Heat and Temperature 7th CBSE Physics
Check point-01 [Formative Assessments]
1. Fill in the blanks
a. Substances which produce large amount of heat on burning are called Fuel.
b. Very low temperature reduce the rate of the growth of bacteria
c. Degree of hotness of a body is called its temperature.
d. Hotness and coldness are comparative term, not absolute.
e. Change of the state is caused by heating or cooling a substance.
f. First stem engine invented by James watt based on the principal of Transformation of energy.
2. What type of energy change takes place in:
a. Thermal power Station: heat energy ®Electrical Energy
b. Nuclear power station: Nuclear energy ® Heat energy ® Electrical Energy
Check point-02 [Formative Assessments]
Fill in the blanks
a. Sir Thomas Clifford Albutt in 1866 invented Clinical thermometer.
b. Thermometer is used to measure temperature.
c. The most commonly use scale to measure temperature is the Celsius scale
d. In the Celsius scale freezing point of water is 00 C and boiling point is 1000C
e. Lab thermometer can measure temperature safely from 00 C to 1000C.
f. The average body temperature is 370C or (98.40C)
g. The highest reading on clinical thermometer is 420C.
h. An object expands on heating and contracts on cooling.
i. The heat can cause change of state in object.
State True and False:
a. A clinical temperature measure temperature up to 1200C [F]
b. A laboratory thermometer has kink in its capillary [F]
c. The degree of hotness cannot be estimated by touching and feeling [T]
d. Disposing of broken thermometer is common trash is harmful to environment [T]
Practice: Answer these Questions:
1. Q. Does every human being have exactly the same body temperature?
Answer: No. every human being have little variation in body temperature
2. Q. What is the range of clinical thermometer?
Answer: 350C to 420C
3. Q. Why does not a clinical thermometer contain marking above 420C?
Answer: This is because no human can survive above 420C.
4. Q. Can a clinical thermometer used to measure temperature of boiling milk? Give reason?
Answer: No, because boiling point of milk is more than 1000C which is above highest marking of clinical thermometer.
5. Q. Why is the stem of thermometer made up of glass?
Answer: The stem of thermometer made up of glass so that reading became easy
6. Q. Paper and dry cloth catch fire easily. Why are they not used as a fuel?
Answer: Paper and dry cloth catch fire easily but cannot produce large amount of heat so they are not used as a fuel.
7. Q. Why a laboratory thermometer cannot be used to measure body temperature?
Answer: Ans: There is no ‘kink’ in laboratory thermometer. Therefore the temperature will fall as soon as we remove the thermometer from the mouth and we will not be able to measure the correct temperature of the body.
8. Q. Why kink is provided in the capillary of clinical thermometer?
Answer: kink is provided in the capillary of clinical thermometer to prevent level of mercury from falling back.
9. Q. Why drinking water recommended to boil and filtered before using?
Answer: Drinking water contain gem that is fatal for body so we recommended to boil and filtered before using water to kill bacteria.
10. Q. What are the differences between clinical and lab Thermometer?
Answer: (a) A clinical thermometer reads temperature from 35OC to 42OC, while a laboratory thermometer ranges between –10OC to 110OC.
(b) Clinical thermometer has a kink near the bulb while there is no kink in laboratory thermometer.
11. Q. How does digital thermometer measure temperature?
Answer: Digital thermometers provide an easy-to-read, LCD display. The heat sensor within the digital thermometer reads the temperature of body and displays it.
12. Q. Why liquid mercury used in thermometer?
Answer: Mercury is used in thermometer because of following reasons:
i) It does not stick to the walls of capillary tube.
ii) Its silvery shine helps us to see temperature accurately.
iii) Its expansion is uniform.
iv) It does not vaporize easily.
13. Q. Why by touching and feeling the hotness of a body is not sufficient to measure temperature?
Answer: Sometime touching and feeling the hotness of a body give us wrong result so touching and feeling the hotness of a body is not sufficient to measure temperature.
14. Q. State two phenomenons involve the transformation of heat energy?
15. Q. How is life of bacteria affected by heat?
Answer: Bacteria cannot grow and multiply at high temperature.
16. Q. State precautions taken while using clinical thermometer?
Answer: We should take following precautions while while using clinical thermometer:-
i)It should be washed before and after using with an antiseptic solution.
ii) We should check or ensures that the mercury level should be 35 degree Celsius before using it.
iii)The reading should be taken while keeping the level of mercury along the line of sight.
iv)W e should not hold the thermometer by its bulb while reading it.
v) We should handle the thermometer with care, as it is breakable.
17. Q. State precautions taken while using Laboratory thermometer?
Answer: precautions taken while using Laboratory thermometer are
a. Bulb of Laboratory thermometer must be in contact of object properly.
b. Reading should be taken without removing from its position.
c. Eyes should be at the vertical level
d. Do not used to measure temperature below - 100C and above 1100C.
18. Q. Why are bottle containing liquid left with some space at the top?
Answer: Bottle containing liquid is left with some space at the top to provide space for expansion of liquid on heating.
19. Q. Why are huge bridge provided with flexible joint?
Answer: flexible joint in huge bridge allow expansion in summer and protect from bending.
20. Define Heat and Energy and temperature.
Answer: According to Rumford and James Prescott, Heat is a form of energy that is known as Thermal Energy. Energy in a substance is due to movement of its molecules.
Energy is capacity to do work. Energy is neither created nor destroyed it can only transformed [changed] one form to another.
Temperature is a measure of the degree of hotness and coldness of an object. S.I unit of Temperature is Kelvin. Other Units are degree Celsius and degree Fahrenheit
Q. (iv) Why digital thermometers are used these days
Ans.: Mercury is a poisonous metal if a thermometer breaks in mouth. . To overcome this, digital thermometers are used these days.
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