Class 7 Science Chapter 4: Heat Extra Questions with Answers
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Fill in the blanks
a. A reliable measure of the hotness of an object is its___________________
b. The range of a clinical thermometer in Celsius scale is_____________________& in Fahrenheit is_____________________________
c. The range of laboratory thermometer is_______________________
d. ____________________________thermometer does not use mercury.
e. Heat is transferred in liquids by________________________
f. We receive heat from sun by__________________________
g. Heat travels through solids by_________________________
h. The maximum and minimum temperatures of the previous day, reported in weather reports, are measured by thermometer called the______________________thermometer.
b.35 to 42 C ,94 to 108 F
c. -10 to 110 C
h. Maximum and minimum thermometer
1.Thermal energy flows between objects due to difference in___________
2.When a liquid is heated it___________
3.Convection current gives rise to ___________
4.Dark colours are good___________ of heat.
5.The degree of hotness or coldness in a substance is called ___________
6.___________ is a conductor of heat.
7.The thermos flask is made up of double walled glass vessels because glass is a ___________
8.In solids transfer of heat can take place by ___________
9.Mercury is a liquid metal in ___________
10.The form of energy that flows from hot object to a cold object is called ___________
11.The boiling point of water in the Celsius scale is ___________
12.The transfer of energy between object that are in physical contact is by ___________
13.The ___________ in a clinical thermometer prevents backflow of the Mercury into the bulb.
14.The handle of cooking utensils are made of material that are___________
15.The vacuum in a thermos flask reduces the heat loss due to___________
7. poor conductor of heat
9. liquid form at room temperature
11. 100 degree Celsius
Multiple Choice Questions
A marble tile would feel cold as compared to a wooden tile on a winter morning, because the marble tile
(a) is a better conductor of heat than the wooden tile.
(b) is polished while wooden tile is not polished.
(c) reflects more heat than wooden tile.
(d) is a poor conductor of heat than the wooden tile Question 4
X and Y measured their body temperature.X found its to be 98.6 °F and Y recorded 37 °C. Which of the followng statement is true?
(a) X has a higher body temperature than Y.
(b) X has a lower body temperature than Y.
(c) Both have normal body temperature.
(d) Both are suffering from fever. Question 5
Identify which one are good conductor and poor conductors of heat
Good conductor -: Aluminium, Copper and Iron
Poor conductor -: Air, water, wood, plastic
Short Answer type questions
Name two good conductors of heat?
Iron, Aluminium, Silver
What is the lowest point of an ordinary laboratory thermometer? Answer
0 degree celsius and -10 degree celsius. Question 9
Why is the bulb of the thermometer made of thin glass?
As glass is a poor conductor of heat, the wall of the bulb is kept thin so that transfer of heat between the Mercury and its surrounding can take place easily.
How is temperature different from thermal energy?
Thermal energy is the sum of energy possessed by all the moving molecules of the substance, while temperature tells how hot or cold a substance is. It is the measure of how fast or slow the molecules are moving.
Temperature indicates the level of thermal energy but it does not tell how much energy is present in the substance.
How do we read a laboratory thermometer?
A laboratory thermometer does not have a construction. It has to be read while it is in contact with the material whose temperature is being measured. For example, to record the temperature of warm water, the temperature has to be read while the thermometer is immersed in warm water.
How does the fur of the polar bear help it to live in the Arctic region?
Air is a good heat insulator. Polar Bears that live in the cold Arctic region have thick layers of fur. The fur traps air and forms an excellent heat insulating layer. The layer of trapped air keeps the animals comfortably warm even when the atmospheric temperature drops below -20 degree Celsius.
Why does cold water kept in an open container become warm on a hot summer afternoon?
Cold water kept in an open container acquires heat from the warmer surrounding air on a hot summer afternoon. As a result cold water will become as warm as the air around it due to transfer of thermal energy.
How do woolen garments keep us warm?
Woollen fibre curls and forms air pockets. The air trapped by a woolen garments is made warm by the heat from the body. This keeps the body warm. Moreover, wool is a poor conductor of heat. It does not let the warmth of the body to escape and also prevents cold air from reaching the body. This is how woolen garments keep the body warm in winter.
Answer the following in one word each:
(a) The SI unit of heat-
(b) The SI unit of Temperature-
(c) The instrument used to measure the temperature-
(d) The transfer of heat from hotter part to a colder part of an object due to vibration of a particles-
(e) The material that do not conduct heat-
b. Kelvin (K)
Convert the given temperature to degree Celsius.
(a) 150 degree F
(b) 48 degree F
Convert the given temperature to degree fahrenheit.
(a) 150 degree C
(b) 32 degree C
Practice Questions Questions
What is the normal temperature of human body in t & F? Question 19
Why is mercury used in thermometers? Question 20
What precautions should be observed while reading a clinical thermometer? Question 21
What precautions should be observed measuring temperature with a laboratory thermometer? Question 22
Give reason why :-
(a) Rooms are provided with ventilators & exhaust fans near top of side walls.
(b) It is advisable to place room heaters at the ground level for effective heating.
(c) Air conditioners should be installed at the top windows. Question 23
Shopkeepers selling ice blocks usually cover them with jute sacks. Explain why.
They must use some insulating material like, sack, saw dust, newspaper, etc. to cover the ice
Explain sea breeze and land breeze with the help of a diagram. Question 25
Why is the box of solar cooker painted black from inside? Question 26
What are the two conditions necessary for the conduction of heat? Question 27
Define the following terms :
v. Radiation Question 28
Define heat? Question 29
What is thermal energy? Question 30
What does the temperature of a substance indicate? Question 31
Write briefly about any two commonly used temperature scales? Question 32
What is a heat insulator? Question 33
How does transfer of heat take place? Question 34
Explain the formation of sea breeze and land breeze? Question 35
How is temperature different from thermal energy? Question 36
Write the difference between the clinical laboratory and maximum minimum thermometers? Question 37
Define the following:
(c) Radiation Question 38
What is the relation between the Celsius scale and the fahrenheit scale? Question 39
Explain the three modes of heat transfer? Which mode of heat transfer takes place in fluid? Question 40
Explain the construction and working of a clinical thermometer with the help of a labelled diagram? Question 41
A liquid having a temperature of 48 degree Celsius and placed on a table acquires a stable temperature of 36 degree Celsius. What is the room temperature and what season could it be? Question 42
Explain the construction and working of a thermos flask with the help of a labelled diagram?
How does a thermos flask maintain the temperature of liquid kept in it?
(a)A thermos flask is used to maintain the temperature of liquids kept in it. It keeps hot liquids hot or cold liquids cold for a longer time.
(b)The glass is made up of a double wall glass vessel with vacuum between the walls.
(c)Glass being a poor conductor of heat, reducing the transfer of heat from inside the flask as well as outside of it.
(d)Heat that could be transferred through radiation is reduced by silvering the walls of the vacuum flask. This reflects the heat rays either trying to enter the flask from outside or leaving the flask from inside.