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  • For a gas, temperature and volume are directly proportional. Keeping everything else constant,

  • as the temperature of a gas goes up, its volume goes up. As the temperature of a gas goes

  • down, its volume goes down.

  • If you heat up a gas, it expands - the gas particles move faster, and they take up more

  • space. Imagine a balloon, that expands when gas particles bang against the sides. (by

  • expanding, that keeps the pressure constant). The faster the gas particles move, the more

  • they will push on the sides of the balloon, expanding it. If, on the other hand, you cool

  • the gas down - you put your balloon on ice - that slows the particles of gas down, so

  • the balloon will contract.

  • Jacques Charles is credited with this Gas Law relating temperature and volume, although

  • he didn’t publish it - he may have been too busy taking rides in hot air balloons.

  • A colleague, Joseph Louis Gay-Lussac, published it and very honorably gave Charles credit.

  • Charles’s Law says that for a given amount of gas, at fixed pressure, volume and temperature

  • are directly proportional. V ∝ T You can write this mathematically as V = kT

  • where V = volume, T = temperature in Kelvin, and

  • k = is a proportionality constant. We can rearrange this equation so it reads

  • V/T = k, or the ratio of volume to temperature is a constant, k.

  • Very often, Charles’s law is used to compare two situations, a “beforeand

  • anafter.” In that case, you can say V1 /T1= k, and V2/T2 = k, so you can write

  • Charles’s law as V1 /T1= V2/T2. Let’s see an example.

  • A hot air balloon has a volume of 2,800 m3 at 99 C°. What is the volume if the air cools

  • to 80 C°? Well write Charles’s Law in thebefore

  • and afterform: V1 /T1= V2/T2.

  • We substitute in what we know - remember to convert temperatures to Kelvin: Kelvin = C° + 273.15.

  • T1= 372.15 Kelvin, T2 = 353.15 Kelvin 2,800 m3/ 372.15 K = V2/ 353.15 K

  • solve for V2 (multiply both sides by 353.15K) (353.15 K) (2,800 m3)/ 372.15 K = V2

  • V2 = 2657 m3

  • Here’s another example: At 0 C°, a gas occupies 22.4L. How hot must the gas be, in

  • Celsius, to reach a volume of 25.0 L? V1 /T1= V2/T2.

  • Convert temperature to Kelvin: Kelvin = C° + 273.15.

  • T1 = 273.15 K Substituting in what we know: 22.4L/273.15K

  • = 25.0L/T2 Solve for T2 (I like

  • tocross multiply”) (22.4L) T2 = (273.15 K)(25.0L)

  • T2 = (273.15K) (25.0L)/22.4L T2 = 304.9 K

  • Convert to C°: C° = Kelvin - 273.15 T2 = 31.7 C°

  • Charles’s law relates temperature and volume for a gas, but there are other gas laws which

  • relate the other essential variables associated with a gas. Boyle’s Law is the relationship

  • between pressure and volume. Gay-Lussac’s Law is the relationship between

  • pressure and temperature. And the combined gas law puts all 3 together: Temperature,

  • Pressure, and Volume. Notice that to use any of these laws, the amount of gas must be constant.

  • Avogadro’s Law describes the relationship between volume and the amount of a gas (usually

  • in terms of n, the number of moles). When we combine all 4 laws, we get the Ideal Gas

  • Law. To decide which of these gas laws to use when solving a problem, make a list of

  • what information you have, and what information you need. If a variable doesn’t come up,

  • or is held constant in the problem, you don’t need it in your equation.

For a gas, temperature and volume are directly proportional. Keeping everything else constant,

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B1 中級

化学.チャールズの法則(気体の法則)2例付き|宿題の家庭教師 (Chemistry: Charles's Law (Gas Laws) with 2 examples | Homework Tutor)

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    林宜悉 に公開 2021 年 01 月 14 日
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