Charles's Law states that the volume of a gas is directly proportional to its absolute temperature when the pressure and the amount of gas are kept constant.
Understanding Charles's Law
Charles's Law, formally known as Charles's and Gay-Lussac's Law, is a fundamental concept in thermodynamics and describes how gases tend to expand when heated.
Key aspects of Charles's Law:
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Direct Proportionality: According to the reference, "the volume occupied by a fixed amount of gas is directly proportional to its absolute temperature, if the pressure remains constant." This means if you double the absolute temperature of a gas, its volume will also double, assuming the pressure doesn't change.
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Constant Pressure: For Charles's Law to hold true, the pressure of the gas must remain constant.
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Absolute Temperature: Temperature must be measured in an absolute scale, such as Kelvin (K). This is because using Celsius or Fahrenheit can lead to incorrect calculations due to the zero point being arbitrarily defined.
Mathematical Representation
Charles's Law can be expressed mathematically as:
V₁/T₁ = V₂/T₂
Where:
- V₁ is the initial volume.
- T₁ is the initial absolute temperature.
- V₂ is the final volume.
- T₂ is the final absolute temperature.
Practical Examples
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Hot Air Balloons: Heating the air inside a hot air balloon increases its volume, making the balloon less dense than the surrounding air and causing it to rise.
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Inflating a Tire: On a hot day, the temperature of the air inside a car tire increases. If the tire cannot expand, the pressure increases. If the tire can expand, the volume increases.
Table Summarizing Charles's Law
| Property | Description | Condition |
|---|---|---|
| Volume | The space occupied by the gas. | Changing (dependent) |
| Temperature | Measured in Kelvin (K). | Changing (independent) |
| Pressure | Force exerted per unit area. | Constant |
| Amount of Gas | The number of moles of gas present. | Constant |
