Charles's Law Calculator
Calculate the direct relationship between Volume and Temperature ($V_1/T_1 = V_2/T_2$).
Initial State (1)
Final State (2)
Visualizing Relationship
The Law of Expansion
Charles's Law explains why hot air rises and why leaving a basketball outside in winter makes it go flat. It is the simple rule that heat makes gas expand.
Direct Proportionality
As Temperature goes UP, Volume goes UP.
Kinetic Theory
Why does this happen? Temperature measures the speed of particles.
- SpeedWhen you heat a gas, the particles move faster and hit the container walls harder.
- PushTo keep pressure constant, the walls must be pushed outward, increasing the space (volume) the gas occupies.
Absolute Zero
This law gave us the first hint that Absolute Zero exists.
Scientists noticed that for every degree Celsius volume dropped, it decreased by 1/273. They realized that at -273°C, volume would theoretically disappear completely. This led to the creation of the Kelvin scale.
Baking Bread
Yeast creates tiny CO2 bubbles. When the loaf hits the hot oven, Charles' Law forces those bubbles to expand rapidly, giving bread its fluffy texture.
Ballooning
Hot air balloons don't use helium. They just use hot air! Heating the air makes it expand and become less dense than the cool air outside, generating lift.
Sports Balls
Don't leave your football outside in the snow. The volume of air inside will shrink, making the ball soft and flat. Bring it inside to warm up, and it re-inflates!
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Frequently Asked Questions
What is Charles's Law?
Charles's Law states that the volume of an ideal gas is directly proportional to its absolute temperature, assuming the pressure remains constant. As you heat a gas, it expands; as you cool it, it shrinks.
What is the formula?
The formula is V1 / T1 = V2 / T2.
- V = Volume (Liters, m³, etc.)
- T = Temperature (Must be in Kelvin)
- Pressure must be constant.
Why must temperature be in Kelvin?
This is the #1 student mistake. The law is based on Absolute Temperature. 0°C is just the freezing point of water, not zero energy. If you used 0°C in the denominator, the math would break (division by zero). You must always add 273.15 to Celsius.
What happens at Absolute Zero?
At 0 Kelvin (-273.15°C), molecular motion stops. If you extrapolate Charles's Law graph backwards, the volume of the gas hits zero at exactly this temperature. It is the theoretical lowest limit of the universe.
What are real-world examples?
Hot Air Balloons: The burner heats the air, increasing its volume. The air becomes less dense than the surrounding cold air, creating lift. Thanksgiving Turkey: The 'pop-up' timer works because the air inside the turkey heats up and expands.
Who discovered this law?
Jacques Charles (a French inventor and balloonist) observed the relationship in 1787. However, he didn't publish it. It was Joseph Louis Gay-Lussac who published the definitive paper in 1802 and credited Charles.
Does this apply to liquids?
Liquids do expand when heated (like mercury in a thermometer), but they don't follow the simple linear relationship of Charles's Law. This law is specifically for gases.
Why does bread rise?
Yeast produces CO2 bubbles in the dough. When you put the dough in a hot oven, Charles's Law takes over: the gas bubbles expand significantly due to the heat, making the bread fluffy.
What is the graph of V vs T?
It is a straight line passing through the origin (if using Kelvin). This linear relationship proves they are directly proportional.
Can I use Fahrenheit?
No. Fahrenheit is not an absolute scale. You must convert it to Rankine or (more commonly) Kelvin. Our calculator handles this for you.
What implies 'Constant Pressure'?
Any situation where the container can expand freely implies constant pressure. Examples: Balloons, Pistons, Syringes, or open-air experiments.
How do I solve for T2?
Rearrange the algebra: T2 = (V2 × T1) / V1. Be careful to plug in T1 in Kelvin!
What is V/T = k?
It means the ratio of Volume to Temperature is always a constant number (k) for a specific sample of gas. If you double T, V must double to keep 'k' the same.
Is Charles's Law accurate for all gases?
It works perfectly for 'Ideal Gases'. For real gases at very high pressures or very low temperatures (near condensation), the law becomes less accurate due to intermolecular forces.
How does it relate to the Ideal Gas Law?
From PV=nRT, if P, n, and R are constant, then V = (nR/P)T. Since (nR/P) is just a constant number, V is directly proportional to T.