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VII-EM-HEAT AND TEMPERATURE -EVALUATION QUESTION AND ANSWERS
Class- VII
HEAT AND TEMPERATURE
EVALUATION
I. Choose the correct answer
1. International unit of measuring temperature is ..........................
a. Kelvin
b. Fahrenheit
c. Celsius
d. Joule
Ans: a. Kelvin
2. In thermometer when bulb comes in contact with hot object, liquid inside it
a. expands
b. contracts
c. remains same
d. none of above
Ans: a. expands
3. The body temperature of a healthy man is;
a. 0°C
b. 37°C
c. 98°C
d. 100°C
Ans: b. 37°C
4. Mercury is often used in laboratory thermometers because it ______________________
a. is a harmless liquid
b. is silvery in colour and is attractive in appearance
c. Expands uniformly
d. is a low cost liquid
Ans: c. Expands uniformly
5. Which of the following temperature conversions is incorrect
K ( Kelvin) = °C ( Celsius) + 273.15
°C K
a. -273.15 0
b. -123. +150.15
c. + 127. + 400.15
d. + 450 + 733.15
Ans: d. + 450 + 733.15
II. Fill in the blanks
1.Doctor uses____________thermometer to measure the human body temperature.
Ans: Clinical
2. At room temperature Mercury is in _______________ state.
Ans: liquid
3. Heat energy transfer from _______________ to ___________.
Ans: hot substance , cold substance
4. - 7°C temperature is ____________ than 0°C temperature.
Ans: lower
5. The common laboratory thermometer is a ______________ thermometer.
Ans: mercury
III. Match the following
Ans:
IV. Give very short answer
1. Temperature of Srinagar (J&K) is -4°C and in Kodaikanal is 3°C which of them has greater temperature ? What is the difference between the temperatures of these two places?
Kodaikanal has greater temperature.
Temperature at Srinagar = -4°C
Temperature at Kodaikanal = 3°C
Temperature difference = - 4°C (-) 3°C
Temperature difference = 7°C
So, Srinagar is colder than Kodaikanal.
2. Jyothi was prepared to measure the temperature of hot water with a clinical thermometer. Is it right or wrong? Why?
It is wrong. The clinical thermometer has the temperature range of 35°C to 42°C.If it is used to measure the temperature of hot water, thermometer glass will crack/burst due to excessive pressure created by expansion of mercury, as the temperature of hot water(100°C) would be more than the range of clinical thermometer.
3. A clinical thermometer is not used to measure the temperature of air, why?
Clinical thermometer is designed to measure the temperature of the human body, the range of a clinical thermometer is also less than that of the temperature of air. So, it cannot be used to measure the temperature of air.
4. What is the use of kink in clinical thermometer?
Clinical thermometers have a kink that prevents the mercury from flowing back into the bulb when the thermometer is taken out of the patient's mouth. So that the temperature can be noted conveniently.
5. Why do we jerk a clinical thermometer before we measure the body temperature?
Jerking the thermometer a few times will allow the level of mercury to bring down to normal temperature.
V. Give short Answer
1. Why do we use Mercury in thermometers? Can water be used instead of mercury? What are the problems in using it?
We use mercury, because it expands in a uniform manner and it’s a good conductor of heat.
Mercury remains in liquid form even with a small and high range of temperature change.
Mercury is shining in nature, so it is easy to read the scales and it does not stick to the sides of the glass.
Water can not be used instead of mercury; because
Water is colourless, it makes it very hard to read the meniscus.
For temperatures above 100°C and below 0°C, the water would boil or freeze making it useless as a temperature measuring device.
2. Swathi kept a laboratory thermometer in hot water for some time and took it out to read the temperature. Ramani said it was a wrong way of measuring temperature. Do you agree with Ramani? Explain your answer.
Yes, I agree with Ramani.
Laboratory thermometer should not be taken out from the liquid while reading the temperature.
Laboratory thermometer does not have a kink, so when it is taken out from the liquid, the level of mercury will go down and show a temperature that differs from actual temperature.
So it is the wrong way to measure the temperature after taking out the thermometer from the liquid.
3. The body temperature of Srinath is 99°F. Is he suffering from fever? If so, why?
The normal temperature of the human body is 98.6°F. Srinanths body temperature is 99°F, which is higher than normal body temperature. So he is suffering from fever.
VI. Give long answer
1. Draw the diagram of a clinical thermometer and label its parts.
2. State the similarities and differences between the laboratory thermometer and the clinical thermometer.
Similarities:
Both the thermometers are made of glass and consist of long narrow glass tubes and have a bulb at one end.
Bulbs of both the thermometers consist of mercury
Differences:
VII. Higher Order Thinking questions
1. What must be the temperature in Fahrenheit, so that it will be twice its value in Celsius?
Basic conversion formula: F = 9/5C + 32
We can say F = 1.8C+32
According to our problem: F = 2C
2C = 1.8C + 32
By rearranging, we will get
(2 - 1.8)C = 32
0.2C = 32
C = 32 / 0.2
= 160°C
F = 2C
F = 2 x 160°C
F = 320°F
2. Go to a veterinary doctor (a doctor who treats animals). Discuss and find out the normal temperature of domestic animals and birds.
