Charles law examples in real life
Charles law states that the volume of a gas is directly proportional to its absolute temperature. Pressure and the amount of gas stay constant.
V1 / T1 = V2 / T2. If the Kelvin temperature doubles, the volume doubles.
- A balloon shrinks in a freezer and expands again in a warm room.
- A hot air balloon rises because the heated air inside expands and becomes less dense than the air outside.
- Bread rises in the oven because gas bubbles in the dough expand as they heat up.
- A dented ping-pong ball pops back into shape in hot water because the air inside expands.
- A balloon dipped in liquid nitrogen collapses. It inflates again as it warms to room temperature.
- A helium balloon left in a hot car can burst because the gas inside expands.
Charles law example problems
Example 1
A balloon holds 2.00 L of air at 25 °C. What is its volume at 75 °C at constant pressure?
- Convert to kelvin: T1 = 298.15 K and T2 = 348.15 K.
- V2 = V1 × T2 ÷ T1 = 2.00 L × 348.15 ÷ 298.15 = 2.34 L.
Answer: 2.34 L
Example 2
A gas occupies 500 mL at 300 K. To what temperature must it be cooled to occupy 400 mL?
- T2 = T1 × V2 ÷ V1.
- T2 = 300 K × 400 mL ÷ 500 mL = 240 K.
Answer: 240 K, or −33 °C
Example 3
A 3.0 L balloon at 20 °C goes into a freezer at −18 °C. What is its new volume?
- Convert to kelvin: T1 = 293.15 K and T2 = 255.15 K.
- V2 = 3.0 L × 255.15 ÷ 293.15 = 2.6 L.
Answer: 2.6 L
Example 4
A gas at 27 °C has a volume of 150 mL. It is heated at constant pressure until its volume doubles. What is the final temperature?
- T1 = 27 + 273.15 = 300.15 K.
- The volume doubles, so the Kelvin temperature doubles: T2 = 2 × 300.15 K = 600.3 K.
- Convert back to Celsius: 600.3 − 273.15 = 327 °C.
Answer: 600 K, or 327 °C
How to use this calculator
- Select V1, V2, T1, or T2 as the unknown.
- Enter the other volume and temperature values.
- Select the units and calculate.
Formula and variables
V1/T1 = V2/T2
| Symbol | Meaning | Unit |
|---|---|---|
| V1, V2 | initial/final volume | compatible volume |
| T1, T2 | absolute temperature | K |
Worked example
A balloon holds 2.00 L at 25 °C. At 75 °C and constant pressure, V2 = 2.00 × 348.15 / 298.15 = 2.34 L.
Interpretation
Volume is proportional to absolute temperature at fixed pressure and amount.
Common mistakes
- Use absolute temperature in Kelvin.
- This relation assumes constant pressure and gas amount.
Frequently asked questions
What is an example of Charles law?
A balloon shrinks in a freezer and expands in a warm room. At constant pressure, gas volume changes with absolute temperature.
Why must the temperature be in Kelvin?
Charles law is a direct proportion with absolute temperature. Celsius has an arbitrary zero, so a Celsius ratio gives a wrong volume.
What stays constant in Charles's law?
Pressure and amount of gas stay constant.
Can I enter a Celsius temperature?
Yes. The calculator converts Celsius to Kelvin before it uses the ratio.
Can the calculator solve for temperature?
Yes. It can solve for either initial or final absolute temperature.
Can I use scientific notation?
Yes. Enter values such as 6.022e23 or 1.0e-6 in a numeric field.
How should I round the result?
Keep extra digits during the calculation. Round the final result to the precision required by your data.