Chapter 4: Heat
Explore the fundamental concepts of heat, temperature, and the three modes of heat transfer: conduction, convection, and radiation.
Key Topics & Objectives
â–¼- Measure Temperature: Understand how clinical and laboratory thermometers work.
- Direction of Heat Flow: Observe heat moving from a hotter to a colder body.
- Modes of Transfer: Study conduction, convection, and radiation.
- Real-World Applications: Discuss clothing preferences and common heat phenomena.
- Temperature & Flow: Simulate measuring temperature and observing heat flow with the virtual controls.
- Conductor/Insulator Challenge: Test different materials for their ability to conduct heat.
- Review the explanations to consolidate your learning.
Experiment 1: Direction of Heat Flow
Observe how heat transfers from a hotter object (high temp) to a colder object (low temp).
Experiment 2: Conduction - Conductors vs. Insulators
Observe the simulated temperature change in different materials after a minute of heating.
The wooden spoon feels "hot" (or in the case of ice-cream, "cold") because it is a **poor conductor of heat**, or an **insulator**. When dipped in ice-cream, the wood does not quickly conduct the heat away from your hand, so it doesn't feel as cold as a metal spoon would. The prompt's question "why a wooden spoon gets hot when dipped in ice-cream" contains a common confusion; it actually *gets cold*, or rather, it doesn't conduct the heat away from the ice-cream (or toward the ice-cream from your hand) very well.
The Physics of Heat Transfer
- Conduction: Heat transfer by direct contact, primarily in solids. Requires a medium.
- Convection: Heat transfer through the movement of fluids (liquids and gases).
- Radiation: Heat transfer via electromagnetic waves, requires no medium (e.g., heat from the sun).
Light-coloured clothes are preferred in summer because they are poor **absorbers** and good **reflectors** of heat radiation. Dark-coloured clothes are preferred in winter because they are good **absorbers** of heat radiation, keeping you warmer.
The **clinical thermometer** has a small **kink or constriction** near the bulb. This prevents the mercury from falling back into the bulb immediately after being removed from the mouth, allowing the temperature to be read. A **laboratory thermometer** lacks this kink, so its reading changes rapidly, making it unsuitable for measuring the human body temperature accurately outside the body.
