CBSE Class 7 Science Heat Worksheet Set 01

Heat

Heat is the form of energy. It is responsible for the change in thermal condition of the body. It may be defined as the energy flow due to a temperature difference.

Calorie

Amount of heat required to raise the temperature of 1 g of water by \(1^\circ\text{C}\) is called 1 calorie.
Or
Amount of heat required to raise the temperature of 1 g of water from \(14.5^\circ\text{C}\) to \(15.5^\circ\text{C}\) is called 1 cal. It is also called international calorie.
1 calorie = 4.285 joule

Temperature

Temperature is the measurement of hotness or coldness of a body.
                                        Or
Temperature is the thermal condition of the body which also determines the direction of flow of heat.

Temperature Scales

Various scales are used for measuring the temperature. These are as follows:

• 1. Centigrade Scale (\(^\circ\text{C}\)) In this scale, ice point and steam point are taken as \(0^\circ\text{C}\) and \(100^\circ\text{C}\). \(1^\circ\text{C}\) is equal to 100th part of difference between two points.
• 2. Fahrenheit Scale (\(^\circ\text{F}\)) In this scale, ice point and steam point are taken as \(32^\circ\text{F}\) and \(212^\circ\text{F}\). \(1^\circ\text{F}\) is equal to the 180th part of difference between two points.
• 3. Kelvin Scale (K) In this scale, ice point and steam point are taken as \(273\text{ K}\) and \(373\text{ K}\). \(1\text{ K}\) is equal to the 100th part of difference between two points.
• 4. Rankine Scale (Ra) In this scale, ice point and steam point are taken as \(460\text{ Ra}\) and \(672\text{ Ra}\). \(1\text{ Ra}\) is equal to the 212th part of difference between two points.
• 5. Reaumer Scale (R) In this scale, ice point and steam point are taken as \(0\text{ R}\) and \(80\text{ R}\). \(1\text{ R}\) is equal to the 80th part of difference between two points.

 

Relation between Various Temperature Scales
\[ \frac{\text{C}}{100} = \frac{\text{F} - 32}{180} = \frac{\text{R}}{80} = \frac{\text{K} - 273}{100} = \frac{\text{Ra} - 460}{212} \]

Temperature	Celsius (\(^\circ\text{C}\))	Fahrenheit (\(^\circ\text{F}\))	Kelvin (K)
Freezing of water	\(0^\circ\text{C}\)	\(32^\circ\text{F}\)	\(273\text{ K}\)
Normal temperature of the room	\(27^\circ\text{C}\)	\(80.6^\circ\text{F}\)	\(300\text{ K}\)
Normal temperature of the human	\(37^\circ\text{C}\)	\(98.6^\circ\text{F}\)	\(310\text{ K}\)
Boiling point of the water	\(100^\circ\text{C}\)	\(212^\circ\text{F}\)	\(373\text{ K}\)

Thermometre

• The devices which measures the temperature of the body, is called thermometre.
• It was developed by Galileo.
• Thermometre has two fix points: upper fix point and lower fix points.
• Thermometers are following types:
  • (i) Clinical thermometre In this thermometre mercury (Hg) is used because of its greater visibility, higher density and do not stick on the wall of vessel.
    It can measure temperature range between \(96^\circ\text{F}\) to \(110^\circ\text{F}\).
    It is used for measuring human body temperature.
  • (ii) Liquid thermometre Alcohol and mercury is used in this thermometre. Its lower fix point is \(-30^\circ\text{ C}\) and upper fix point is \(357^\circ\text{C}\).
  • (iii) Pyrometre It can measure the temperature range between \(-40^\circ\) to \(3500^\circ\text{ C}\). It is used for measuring sun temperature.

 

Principle of Calorimeter
Amount of heat loss = Amount of heat gain

Transmission of Heat

Transfer of heat from one place to other places is called transmission of heat. There are three processes by which transmission of heat takes place.

• 1. Conduction Conduction is that process of transmission of heat in which heat goes from one particle to another particle of substance, but not particle leaves its position. In solids, transmission of heat takes place by conduction process.
  e.g. during winter, iron seems colder and in summer it seems hotter than wood because iron is a good conductor of heat.
• 2. Convection Convection is that process of transmission of heat is which particles of substance go to another place after taking heat from the source, and other particles come to their place.
  In liquids and gases transmission of heat takes place by convection process.
  e.g. Formation of Sea Breeze.
• 3. Radiation Radiation is that process of transmission of heat in which medium is not required for transfer of heat. It is the quickest way of transmission of heat. Heat from the sun comes to the earth by radiation.
  e.g. in deserts, days are very hot, and nights are very cold. This is because of the very low specific heat of sand.

 

Multiple Choice Type Question

Question. Which of the following statement(s) is/are not correct?
(a) Heat is a form of energy
(b) The unit of heat is ohm
(c) Heat flows from a higher temperature body to a lower temperature body
(d) All of the options
Answer: (b) The unit of heat is ohm

Question. 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
Answer: (a) is a better conductor of heat than the wooden tile

Question. When a ring of metal is heated what happens to its hole?
(a) Expands
(b) Contracts
(c) It expands or contracts according to its diameter
(d) It expands or contracts according to is coefficient of expansion
Answer: (a) Expands

Question. Which of the following statement(s) is/are correct?
I. When one end of a metallic rod is heated its other end becomes hot
II. Heat is transmitted from lower temperature to higher temperature body.
(a) Only I
(b) Only II
(c) Both I and II
(d) Neither I nor II
Answer: (a) Only I

Question. On heating one end of iron rod, other end also gets heated. Such materials are called
(a) good conductor of heat
(b) good insulator of heat
(c) semiconductor of heat
(d) heater
Answer: (a) good conductor of heat

Question. The boiling point water is
(a) \(100^\circ\text{C}\)
(b) \(80^\circ\text{C}\)
(c) \(120^\circ\text{C}\)
(d) \(200^\circ\text{C}\)
Answer: (a) \(100^\circ\text{C}\)

Question. The temperature of water at the bottom of a lake whose upper surface has frozen to ice would be around.
(a) \(-10^\circ\text{C}\)
(b) \(0^\circ\text{C}\)
(c) \(4^\circ\text{C}\)
(d) \(-4^\circ\text{C}\)
Answer: (c) \(4^\circ\text{C}\)

Question. When water changes to water vapour, then
(a) no temperature change takes place
(b) no heat flow occurs
(c) heat flows into the water from surrounding heat source
(d) Both (a) and (c)
Answer: (d) Both (a) and (c)

Question. Mercury thermometre was invented by
(a) Fahrenheit
(b) Newton
(c) Priestley
(d) Galileo
Answer: (d) Galileo

Question. A metal X is used in clinical thermometre. It is the only metal which is in liquid state at room temperature. Metal X is
(a) silver
(b) gold
(c) mercury
(d) copper
Answer: (c) mercury

Question. Cooking is difficult on hills because
(a) atmospheric pressure is higher
(b) atmospheric pressure is lower
(c) boiling point of water is reduced
(d) Both (b) and (c)
Answer: (d) Both (b) and (c)

Question. Water pipes burst in severe winter at hill stations because
(a) they contract on cooling
(b) water in the pipe contracts on freezing
(c) water in the pipe expands on freezing
(d) pipes expand on cooling
Answer: (c) water in the pipe expands on freezing

Question. Woollen clothes are warmer than the cotton ones because
(a) they are better absorbers of heat
(b) they are better insulators of heat
(c) they are better radiators of heat
(d) they are heavier than cotton clothes
Answer: (b) they are better insulators of heat

Question. A white and smooth surface is
(a) bad absorber and good reflector of heat
(b) good absorber and bad reflector of heat
(c) bad absorber and bad reflector of heat
(d) good absorber and good reflector of heat
Answer: (a) bad absorber and good reflector of heat

Question. The amount of heat that a body can absorb by radiation
(a) depends on colour and temperature both of body
(b) depends on colour of body only
(c) depends on temperature of body only
(d) depends on density of body
Answer: (a) depends on colour and temperature both of body

Question. With the increase in temperature, the density of a substance, in general,
(A) increases
(B) decreases
(C) first increase then decreases
(D) first decrease then increases
Answer: B

Question. When an inflated tyre bursts, the air escaping out
(A) will get heated up
(B) will be cooled
(C) will not undergo any change in its temperature
(D) will be liquefied
Answer: B

Question. A circular disc of copper has a symmetrical hole at its centre. The disc is uniformly heated. The diameter of the hole will
(A) increase
(B) decrease
(C) remain the same
(D) become indeterminate
Answer: A

Question. Heat flows as a result of difference of
(A) temperature
(B) weight
(C) mass
(D) none of these
Answer: A

Question. Two spheres of the same size are made of the same material, but one is hollow and the other is solid. They are heated to the same temperature.
Then,
(A) the hollow sphere will expand more
(B) the solid sphere will expand more
(C) both spheres will expand almost equally
(D) only the solid sphere will expand
Answer: C

Question. Water evaporates under atmospheric pressure. Without changing the temperature, the same water is placed under partial vacuum. The rate of evaporation will
(A) increase
(B) drop to zero
(C) decrease
(D) remain unaffected
Answer: A

Question. The Sl unit for the coefficient of linear expansion is
(A) °C
(B) per°C
(C) cm2/°C
(D) none of these
Answer: D

Question. When water is heated from 0°C, its volume
(A) increases
(B) decreases till 4°C
(C) remains the same
(D) first increases then decreases
Answer: B

Question. The unit for the coefficient of real expansion is
(A) cm
(B) cm/°C
(C) cm °C
(D) /°C
Answer: D

Question. Absolute zero corresponds to
(A) –273 K
(B) 273°C
(C) 273° R
(D) none of these
Answer: D

Question. The SI unit for the coefficients of cubical expansion is
(A) °C
(B) per°C
(C) cm²/°C
(D) none of these
Answer: D

Question. When salt is properly mixed with ice, the melting point of ice
(A) is lowered
(B) is raised
(C) remains the same
(D) becomes infinite
Answer: A

Question. The unit of specific heat is
(A) cal°C
(B) cal/g/°C
(C) cal/g
(D) none of these
Answer: B

Question. If 10 g of ice at 0°C mixes with 10 g of water at 0°C, then the final temperature t is given by
(A) (10 × 80) + l0(t – 0) = 10(10 – t)
(B) 10 × 80 = 10(10 – t) + 10(t – 0)
(C) t = 5°C
(D) t = 0°C
Answer: D

Question. A thermos bottle containing coffee is vigorously shaken. If the coffee is considered as a system, then the temperature of the coffee will
(A) increase slightly
(B) fall
(C) remain the same
(D) never be determined
Answer: A

Question. The unit of thermal capacity is
(A) cal°C
(B) cal/g
(C) cal/g/°C
(D) none of these
Answer: A

Question. The unit for the coefficient of apparent expansion is
(A) cm
(B) cm/°C
(C) cm °C
(D) /°C
Answer: D

Question. The most commonly used thermometric substance is
(A) water
(B) Alcohol
(C) mercury
(D) None of these
Answer: C

Question. The normal temperature of the human body is
(A) 37°C
(B) 38°C
(C) 36.8°C
(D) none of these
Answer: A

Question. Glaciers always melt at the first.
(A) top surface
(B) sides
(C) bottom
(D) middle surface
Answer: C

Questions

            Very Short Answer

Q1)      How do we find out how hot or cold an object is?

Q2)      What is clinical thermometer?

Q3)      What is the range of the laboratory temperature?

Q4)      What is thermometer?

Q5)      How woollen clothes keep us warm in winter?

           

            Short Answer

Q6)      What do you mean by the maximum minimum temperature?

Q7)      Why do darker colours absorb more heat than lighter colours?

Q8)      Why containers are with white and black surface?

Q9)      What is the use of the kink in the thermometer?

Q10)    How can we lift a hot pan by holding it form the handle without getting hurt?

           

            Long Answer

Q11)    State the difference between clinical thermometer and laboratory thermometer?

Q12)    How conductors are different from insulators?

Q13)    What are the precautions to be observed while using a clinical thermometer?

Q14)    Distinguish between sea breeze and land breeze?

Q15)    Difference between convection and radiation?

 

Please click on below link to download CBSE Class 7 Science Heat Worksheet Set A