Unit Test(Solutions): Heat | Science Class 7 (Old NCERT) PDF Download

Time: 1 hour

Maximum Marks: 30

Attempt all questions.

Question numbers 1 to 5 carry 1 mark each.

Question numbers 6 to 8 carry 2 marks each.

Question numbers 9 to 11 carry 3 marks each.

Question numbers 12 & 13 carry 5 marks each.

Q1: Fill in the blank: The temperature of boiling water cannot be measured by a __________ thermometer. (1 Mark)

Ans: Clinical

Q2: Which of the following is a poor conductor of heat? (1 Mark)
(i) Iron
(ii) Copper
(iii) Plastic
(iv) Aluminum

Ans: (iii)
Plastic is a poor conductor of Heat.

Q3: Match the following:

Ans:

Conduction - (c) Transfer of heat through solids

Radiation - (a) Transfer of heat without a medium

Convection - (b) Transfer of heat through liquids and gases

Q4: True or False: Dark-coloured clothes absorb more heat than light-coloured clothes.(1 Mark)

Ans: True
Dark-coloured clothes absorb more heat than light-coloured clothes as light coloured clothes reflect heat.

Q5: Which of the following is an example of heat transfer through convection? (1 Mark)
(i) Heating a metal rod in a flame
(ii) Boiling water in a pot
(iii) Feeling the warmth of the sun
(iv) Ironing clothes with a hot iron

Ans: (ii) 
Convection is the transfer of heat through the movement of fluids (liquids or gases). Boiling water in a pot is an example of convection, where hot water rises and cooler water sinks, creating a circulation of heat.

Q6: What precautions should be taken while using a clinical thermometer? (2 Marks)

Ans: 

• Wash the thermometer before and after use, preferably with an antiseptic solution.
• Ensure the mercury level is below 35°C before using it.
• Read the thermometer by keeping the mercury level at eye level.
• Do not hold the thermometer by the bulb while reading.
  

Q7: Explain the difference between conductors and insulators with examples.(2 Marks)

Ans:

Q8: What happens when you dip a steel spoon in a cup of hot tea? Explain the process involved. (2 Marks)

Ans: When you dip a steel spoon in hot tea, heat is transferred from the hot tea to the spoon through the process of conduction. As steel is a good conductor, the other end of the spoon also becomes hot.

Q9: List six precautions to be taken while reading a laboratory thermometer. (3 Marks)

Ans:

• Hold the thermometer upright and ensure it is not tilted.
• Ensure the bulb is fully immersed in the substance being measured.
• The bulb should not touch the sides or bottom of the container.
• The mercury level should be steady before reading.
• Always read the thermometer at eye level.
• Do not use a laboratory thermometer to measure body temperature.
  

Q10: Explain the three methods of heat transfer in detail and give one example for each. (3 Marks)

Ans:

• Conduction: The process by which heat is transferred from the hotter part of a solid to the cooler part without the movement of the material itself. Example: Heat transfer through a metal rod.
• Convection: The transfer of heat in liquids and gases where the warmer part of the liquid or gas moves to the cooler area. Example: Boiling water in a pot.
• Radiation: The transfer of heat without the need for a medium. Heat is transferred through electromagnetic waves. Example: Heat from the Sun reaching the Earth.

Q11: What are the differences between a clinical thermometer and a laboratory thermometer? (3 Marks)
Ans: 

Clinical Thermometer Below oneQ12: Describe how you would perform an activity to demonstrate convection in water. (5 Marks)

Ans: