🌡️ 1. Heat vs Temperature — What's the Difference?
| Feature |
Heat |
Temperature |
| What it is |
A form of energy that flows from hot to cold |
A measure of how hot or cold an object is |
| Unit |
Joule (J) or Calorie (cal) |
Degree Celsius (°C), Kelvin (K), Fahrenheit (°F) |
| Measured by |
Calorimeter |
Thermometer |
| Example |
A large pot of warm water has more heat than a small cup of boiling water (more water = more
heat energy) |
The boiling water has higher temperature despite less total heat |
Heat flows from a hotter object to a cooler object (never the other way!). They stop
exchanging heat when they reach the same temperature (thermal equilibrium).
🌡️ 2. Thermometer — Measuring Temperature
A thermometer is an instrument used to measure temperature. Most common type
uses mercury (a liquid metal) or alcohol in a glass tube.
Two types of thermometers:
- Clinical/Medical Thermometer: Measures human body temperature. Range: 35°C to 42°C
(or 94°F to 108°F). Has a kink/constriction to prevent mercury from falling back (so reading stays
stable after removal from mouth/armpit)
- Laboratory Thermometer: Has a wider range, usually −10°C to 110°C. No constriction
(bulb must stay in liquid). Used for experiments. Should NOT be tilted or removed while reading
Normal human body temperature = 37°C (98.6°F)
📸 AI Image Prompt
A side-by-side educational comparison of two thermometers: Left: "Clinical
Thermometer" — detailed glass thermometer with a mercury bulb at the bottom, the scale showing 35°C to
42°C with an arrow pointing to the "Kink/Constriction" in the glass tube near the bulb (labeled
"Prevents mercury from falling back"), and a reading indicator at 37°C labeled "Normal Body Temp".
Right: "Laboratory Thermometer" — a taller, straight glass thermometer with a wider scale from −10°C to
110°C, no constriction, with the bulb dipped in a glass of colored liquid, labeled "Must remain in
liquid during measurement". Both thermometers show clear scale markings and mercury column in red. White
background, clean scientific diagram style with bold labels and arrows.
Fig. 3.1 — Clinical vs Laboratory Thermometer
🔥 3. Transfer of Heat — 3 Methods
Heat always flows from a hotter body to a cooler body. It can travel in three ways:
⬇
CONDUCTION
Heat passes through a
solid — particle to particle without the particles moving from place
E.g. A
metal spoon in hot tea gets warm. Cooking on metal pan.
CONVECTION
Heat transferred through
liquids and gases — particles actually move carrying heat energy
E.g.
Boiling water in a pot. Sea breeze. Hot air balloon. Land/sea breeze.
RADIATION
Heat transferred through
empty space (vacuum) — NO medium needed. Travels as electromagnetic waves.
E.g. Heat
from the Sun reaching Earth. Sitting near a campfire. Infrared heater.
📸 AI Image Prompt
A three-panel educational diagram of heat transfer methods: Panel 1 "Conduction" —
a metal rod with the left end in a flame. Glowing orange circles (atoms) are shown vibrating and passing
energy to neighbors in a chain reaction from left (hot, bright orange) to right (cooler, pale). Arrow
shows heat direction. Label: "Solids — particle vibration, no movement". Panel 2 "Convection" — a pot of
water on a stove with circular current arrows inside showing hot water rising from the bottom (marked
HOT, red arrows going up) and cool water sinking from top (marked COOL, blue arrows going down), forming
convection currents. Label: "Liquids and Gases — particles move in currents". Panel 3 "Radiation" — the
Sun on the left, with wavy red/orange radiation lines spreading outward through empty black space,
reaching Earth on the right. Label: "No medium needed — travels through vacuum". Each panel has a bold
title and clear example. White background, educational science illustration, warm color palette.
Fig. 3.2 — Three methods of heat transfer: Conduction, Convection, Radiation
🔑 4. Conductors and Insulators of Heat
| Type |
Definition |
Examples |
Uses |
| Good Conductors |
Allow heat to pass through them easily |
All metals (copper, iron, aluminium, steel), Mercury |
Cooking pots, heat sinks, radiators, frying pans |
| Poor Conductors (Insulators) |
Do NOT allow heat to pass through easily |
Wood, plastic, rubber, glass, wool, cotton, cork, air |
Handles of cooking pots, thermos flask, winter clothing, oven mitts |
Why do woollen clothes keep us warm?
Wool traps air in tiny pockets between its fibres. Air is a very poor conductor (insulator)
of heat. So heat from our body cannot escape outward easily — we stay warm!
Thermos flask (vacuum flask): Has a double glass wall with vacuum between them (no medium
for conduction/convection), and the glass walls are silvered (to reflect radiation). This keeps hot things
hot and cold things cold!
🌡️ 5. Temperature Conversion
Celsius ↔ Fahrenheit:
°F = (°C × 9/5) + 32
°C = (°F − 32) × 5/9
Key reference points:
Water freezes: 0°C = 32°F | Water boils: 100°C = 212°F | Normal body temp: 37°C = 98.6°F
📝 6. Quick Revision
- Heat = form of energy (Joules). Temperature = degree of hotness
(°C). Heat flows hot → cold
- Clinical thermometer: 35°C–42°C; has kink to hold reading. Normal body temp =
37°C
- Laboratory thermometer: −10°C to 110°C; no kink; must stay in liquid while reading
- Conduction = heat through solids (particle vibration; no particle movement). Metals
= good conductors
- Convection = heat through liquids/gases (particles move in currents). E.g. boiling
water, sea breeze
- Radiation = heat through vacuum/space (no medium needed). E.g. Sun's heat reaching
Earth
- Wool traps air → air is insulator → keeps body warm
- Thermos flask: vacuum (blocks conduction/convection) + silvered walls (blocks radiation)
