Thermal Process (chapter 9)

Thermal equilibrium

Thermal equilibrium describes a state in which two or more objects have the same temperature amid that the ire is no net transfer.

Conduction

Conduction is the process of energy transfer where energy is transferred through passing on of vibrational motion from one particle to another.

Conduction In solids (non- metals)

1. Energy is transferred to the rod by heating . The particles nearest to the heat source will vibrate more vigorously about their fixed positions.

2. Thus, through , collisions, energy is transferred from the more energetic particles to the less energetic particles toward the right.

3. Hence, a more energy is transferred from left to right, the particles here begin to vibrate more vigorously. The temperature of this end of the rod increases

Metals:

1. In addition to the sam process in non-metals, the electrons at the heated end gain energy from interacting with the particles. the small size and high speed of the electrons allow them to move easily ands quickly to the cooler end and transfer energy to the particles end,

2. The free electrons moving here are collectively slower after colliding and transferring their energy to the particles at this cooler end. The particles vibrate more vigorously. The temperature at this end of the rod increases

Convection

Convection is a process of energy transfer by means of convection currents of a fluid, due to a difference in density.

1. The liquid at the bottom of the pot expands due to heating via conduction through the bottom of the pot.

2. The warmer and less dense liquid starts rising towards the top.

3. At the same time, the surrounding liquid sinks to take place of the rising liquid. The process repeats and causes convection currents carry waterier liquid away from the heat source and cooler liquid towards it. This allows the pot of liquid to gain internal energy.

Radiation

Radiation is the process of energy transfer by electromagnetic waves. It does not require a medium.

The rate at which an object emits or absorbs radiation is affected by:

• Surface temperature → the higher the temperature of an object’s surface, the higher rate of emission of radiation.

• Surface area→ A larger surface will emit/absorb energy at a higher rate via radiation.

• Surface colour and Texture → Shiny, smooth and light-coloured surface will have a slower rate of emission. → matt,rough and dark coloured surface have a faster rate of emission or absorption.