- Select a substance from the configuration panel.
- Choose Solid, Liquid, or Gas from the Matter Controls panel.
- Click Heat to increase temperature.
- Click Cool to decrease temperature.
- Watch the thermometer level rise or fall.
- Observe how particles move in each state.
- In solid, particles vibrate in fixed positions.
- In liquid, particles slide past each other.
- In gas, particles move freely and fill the container.
- Use the expansion view to study particle motion, thermal expansion, or linear expansion.
- Click Record Observation to save the trial in the table.
Heat energy affects matter in three important ways:
- It can increase the temperature of a substance.
- It can change the state of matter.
- It can cause expansion.
Particle behavior:
- Solid particles are closely packed and vibrate in fixed positions.
- Liquid particles are close together but can move and slide past each other.
- Gas particles are far apart and move freely in all directions.
Heating effect:
- Heating increases particle kinetic energy.
- Particles move faster when temperature increases.
- Solids show stronger vibration and slight expansion.
- Liquids move faster, collide more, and expand moderately.
- Gases move very fast, collide with walls, and expand the most.
Cooling effect:
- Cooling decreases particle kinetic energy.
- Particles move slower when temperature decreases.
- Solids return close to normal spacing.
- Liquids settle closer at the bottom.
- Gases move slowly but still remain far apart.
Thermal expansion:
Thermal expansion is the increase in dimension of a substance due to rise in temperature.
Expansion comparison:
Solid expansion < Liquid expansion < Gas expansion
Important formulas:
K = °C + 273
Linear expansion:
ΔL = αL₀ΔT
Coefficient of linear expansion:
α = ΔL / (L₀ΔT)
Where:
ΔL = change in length
α = coefficient of linear expansion
L₀ = original length
ΔT = change in temperature
SI unit of coefficient of linear expansion:
K⁻¹
Heat energy units:
- Calorie: Heat energy required to raise the temperature of 1 gram of water by 1 °C.
- Kilocalorie: Heat energy required to raise the temperature of 1 kilogram of water by 1 °C.
- 1 kilocalorie = 1000 calories.
Example 1: Thermometer
When a thermometer is placed in warm water, the mercury or liquid inside it expands. So, the
liquid level rises in the narrow tube. This shows expansion of liquid due to heat.
Example 2: Solid rod
When a metal rod is heated, its atoms gain energy and vibrate more strongly. Because of this,
the rod expands slightly in length. This is called linear expansion.
Example 3: Liquid
When a liquid is heated, its particles move faster and spread slightly. So, the liquid level
rises in the container.
Example 4: Gas
When gas is heated, gas particles move very fast and collide with the container walls more
often. Gas expands more than solids and liquids.
