Science · Class 7
Heat
Hot and cold objects, thermometer, conduction, convection, and radiation.
4 sections15–25 min read6 MCQs · 2 examples
Chapter Overview
Heat flows from hotter to colder body until thermal equilibrium. This chapter covers temperature measurement, laboratory and clinical thermometers, conductors and insulators of heat, and modes of transfer — conduction, convection, radiation.
Temperature and Measurement
- Hotness measured by temperature
- Clinical thermometer: 35°C–42°C, kink prevents backflow
- Lab thermometer: wider range, no kink — cannot tilt while reading
- SI unit: degree Celsius (°C); Kelvin in SI system
Transfer of Heat
- Conduction: through solids without bulk movement (metal spoon in hot tea)
- Convection: in fluids — hot fluid rises, cold sinks
- Radiation: no medium needed (Sun's heat)
Conductors and Insulators
- Good conductors: iron, copper, aluminium
- Insulators: wood, plastic, air, wool
- Dark surfaces absorb radiation better; light surfaces reflect
Solved Examples
Step-by-step solutions — read each step before checking the final answer.
Conduction
Why does metal feel colder than wood at same room temperature?
- 1Metal conducts heat away from hand faster
- 2Wood is insulator — less heat loss from skin
- 3Same temperature, different feel
Answer
Metal conducts heat faster from your hand
Sea breeze
Explain sea breeze in afternoon.
- 1Land heats faster than water
- 2Warm air over land rises
- 3Cool sea air moves inland
Answer
Convection due to unequal heating of land and sea
Key Points to Remember
- ✓ Heat and temperature are different quantities
- ✓ Mercury and alcohol used in thermometers
- ✓ Wool traps air — good insulator
Exam Tips
- • Draw labelled clinical thermometer
- • Give examples of conduction, convection, radiation
- • Why wear light clothes in summer?
Practice MCQs — Heat
Test your understanding with topic-wise multiple choice questions. Explanations appear after each answer.
Question 1 of 6Score: 0/0
Heat flows from: