Class 7 Science

Chapter 4: Heat

STAGE 0: Foundation / Basics

We feel heat when an object is hot. Heat is a form of energy.

Heat can move from a hot object to a cold object.

Objects can be hot, warm, or cold.

STAGE 1: Hot and Cold Objects

Our sense of touch is not always reliable to judge temperature.

To measure how hot or cold an object is, we use a thermometer.

Temperature

Temperature tells us how hot or cold an object is.

The SI unit of temperature is degree Celsius (°C).

Thermometers

Types of thermometers:

• Clinical thermometer – used to measure body temperature
• Laboratory thermometer – used in laboratories

Normal human body temperature is 37°C.

Transfer of Heat

Heat is transferred in three ways:

• Conduction – transfer of heat through solids
• Convection – transfer of heat through liquids and gases
• Radiation – transfer of heat without any medium

Conduction

Heat travels from one particle to another in solids.

Metals are good conductors of heat.

Convection

Heat transfer by movement of liquids and gases.

Hot air rises and cold air sinks.

Radiation

Heat reaches us from the sun by radiation.

No medium is required for radiation.

STAGE 2: NCERT Textbook Questions & Answers

Q1. Name the three methods of heat transfer.

Conduction, Convection, Radiation

Q2. Which thermometer is used to measure body temperature?

Clinical thermometer

Q3. What is normal body temperature?

37°C

STAGE 3: Exam-Oriented Questions

Fill in the blanks:

• Heat flows from a hot object to a cold object.
• Metals are good conductors of heat.

Very Short Answer:

Which method of heat transfer needs no medium?
Answer: Radiation

Quick Revision Points

• Heat is a form of energy
• Temperature is measured using thermometer
• Heat transfers by conduction, convection, radiation
• Normal body temperature is 37°C