Class 7 Science Chapter 3 Important Question Answers - Heat

Very Short Answer Type Questions

Q1: What are woollen clothes made from?
Ans: Woollen clothes are made from the wool obtained from animals like sheep, goats, and yaks.

Q2: Why are light-colored clothes preferred during summer?
Ans: Light-colored clothes are preferred during summer because they reflect heat and help keep the body cool.

Q3: Who devised the Celsius scale for measuring temperature?
Ans: Swedish astronomer Anders Celsius devised the Celsius scale in 1742.

Q4: What is the freezing point and boiling point of water in Celsius and Fahrenheit scales?
Ans: In Celsius, water freezes at 0°C and boils at 100°C. In Fahrenheit, water freezes at 32°F and boils at 212°F.

Q5: What is the purpose of a thermometer?
Ans: A thermometer is used to measure the temperature of an object, indicating how cold or hot it is.

Q6: Who invented the mercury thermometer?
Ans: Gabriel Fahrenheit invented the mercury thermometer in 1714.

Q7: What precautions should be taken when using a clinical thermometer?
Ans: Precautions include washing the thermometer before and after use, not holding it near the bulb, and placing the mercury level along the eyesight.

Q8: What is the temperature range for a healthy person's body temperature in Fahrenheit?
Ans: A healthy person's average body temperature ranges from 98.6°F to 98.8°F.

Q9: What are conductors and insulators of heat?
Ans: Conductors allow the flow of heat, while insulators do not. Examples of conductors include copper and iron, while wood and rubber are insulators.

Q10: How does heat transfer occur in convection?
Ans: Heat transfer in convection occurs through the movement of particles in a medium, such as liquids or gases.

Short Answer Type Questions

Q11: Explain why light-colored clothes are preferred in hot weather.
Ans: Light-colored clothes are preferred in hot weather because they reflect heat rather than absorbing it. This helps in keeping the body cool by reducing the amount of heat absorbed by the clothing.

Q12: Describe the Celsius and Fahrenheit temperature scales and their freezing and boiling points for water.
Ans: The Celsius scale was devised by Anders Celsius, with 0°C as the freezing point of water and 100°C as the boiling point. In the Fahrenheit scale, water freezes at 32°F and boils at 212°F.

Q13: What is the significance of the kink in a clinical thermometer?
Ans: The kink in a clinical thermometer prevents the mercury from falling down rapidly after use, allowing the temperature to be noted conveniently and accurately.

Q14: How do laboratory thermometers differ from clinical thermometers?
Ans: Laboratory thermometers have a longer stem and bulb compared to clinical thermometers. They also typically have only the Celsius scale, and they are used for measuring higher temperatures.

Q15: Explain the three modes of heat exchange: conduction, convection, and radiation.
Ans: Conduction is the transfer of heat within an object without the movement of particles. Convection is the transfer of heat through the movement of particles in a medium like liquids and gases. Radiation is the transfer of heat through electromagnetic waves, such as from the sun to the Earth.

Q16: Why is wool considered a good choice for winter clothing?
Ans: Wool is a good choice for winter clothing because it is an excellent insulator and a poor conductor of heat. It traps air between its fibers, creating an insulating barrier that prevents the flow of heat from the body to the cold surroundings, thus keeping the body warm.

Q17: How do light-colored and loose-fitting clothes help in summer?
Ans: Light-colored clothes reflect heat, keeping the body cooler. Loose-fitting clothes allow air to circulate, promoting cooling through evaporation of sweat.

Q18: Why is it important to use digital thermometers instead of mercury thermometers?
Ans: It is important to use digital thermometers because mercury is toxic, and it can be hazardous if a mercury thermometer breaks. Digital thermometers do not contain mercury and are safer to use.

Q19: How does heat transfer occur in conduction, and give an example?
Ans: Heat transfer in conduction occurs when heat is transferred from a hotter part of an object to a colder part through direct contact. An example is when popcorn is popped in a cooker on a flame, and heat is transferred from the flame to the corn kernels.

Q20: What are conductors and insulators of heat? Provide examples of each.
Ans: Conductors are materials that allow the flow of heat, such as copper and iron. Insulators are materials that do not allow the flow of heat, such as wood, rubber, and glass.