Overview
This lecture explains the direct relationship between the volume and temperature of a gas (Charles's Law), demonstrates a sample calculation, and emphasizes the importance of using Kelvin temperature for these problems.
Relationship Between Volume and Temperature
- As the temperature of a gas increases, its volume increases if pressure is constant (direct relationship).
- Lowering the temperature causes gas particles to move slower, decreasing the volume.
- Kinetic theory explains that gas particles move faster at higher temperatures, requiring more space.
Charles's Law
- Charles's Law describes the relationship between the volume and temperature of a gas at constant pressure.
- The law is mathematically expressed as: V₁/T₁ = V₂/T₂.
- "V" is the volume of the gas; "T" is the temperature in Kelvin.
- When solving problems, always use Kelvin for temperature.
Using Kelvin Temperature
- To convert Celsius to Kelvin, add 273 to the Celsius temperature.
- Temperature in all gas laws must be in Kelvin, not Celsius.
Example Problem: Volume Change with Temperature
- Initial volume (V₁): 625 liters at 0°C.
- Final temperature (T₂): 80°C.
- Convert temperatures to Kelvin: T₁ = 273 K, T₂ = 353 K.
- Rearranged formula: V₂ = V₁ × (T₂/T₁).
- Calculation: 625 L × (353 K / 273 K) = 808 liters (rounded to three significant figures).
Key Terms & Definitions
- Kinetic Theory — Model describing particles in a gas moving faster at higher temperatures.
- Charles's Law — The volume of a gas is directly proportional to its Kelvin temperature at constant pressure.
- Kelvin (K) — Absolute temperature scale used for gas law calculations; 0 K is absolute zero.
Action Items / Next Steps
- Always convert Celsius temperatures to Kelvin before solving gas law problems.
- For deeper understanding or historical background, review the Charles's Law video or materials on absolute zero.