(POM) Gas Laws Lesson

Gas Laws

Boyle's Law

Robert Boyle (1627-1691), an English chemist, discovered that doubling the pressure of an enclosed sample of gas while keeping its temperature constant caused the volume of the gas to be reduced by half. Boyle's Law states that the volume of a given mass of gas varies inversely with the pressure when the temperature is kept constant. An inverse relationship means that as one variable increases in value, the other variable decreases.

Boyle's Law can be used to compare changing conditions for a gas. We use P ₁ and V ₁ to stand for the initial pressure and initial volume of a gas. After a change has been made, P ₂ and V ₂ stand for the final pressure and volume. The mathematical relationship of Boyle's Law becomes:

P ₁ × V ₁ = P ₂ × V ₂

This equation can be used to calculate any one of the four quantities if the other three are known.

Use the following information to get another look at Boyle's Law. There will be a couple of questions at the end to test to see how well you understand Boyle's Law.

Charles's Law

French physicist, Jacques Charles (1746-1823), studied the effect of temperature on the volume of a gas at constant pressure. Charles's Law states that the volume of a given mass of gas varies directly with the temperature of the gas when the pressure is kept constant.

Charles's Law can also be used to compare changing conditions for a gas. We will use V ₁ and T ₁ to stand for the initial volume and temperature of a gas, while V ₂ and T ₂ stand for the final volume and temperature. The mathematical relationship of Charles's Law becomes:

$LaTeX: \frac{V_1}{T_1}=\frac{V_2}{T_2}$ $\frac{V_1}{T_1}=\frac{V_2}{T_2}$

This equation can be used to calculate any one of the four quantities if the other three are known.

Use the following information to get another look at Charles's Law. There will be a couple of questions at the end to test to see how well you understand Charles's Law.

The Combined Gas Law

To this point, we have examined the relationships between any two of the variables P, V, and T, while the third variable is held constant. However, situations can also arise where all three variables change. The combined gas law expresses the relationship between the pressure, volume, and absolute temperature of a fixed amount of gas. For a combined gas law problem, only the amount of gas is held constant.

The mathematical equation is as follows:

$LaTeX: \frac{P_1\times V_1}{T_1}=\frac{P_2\times V_2}{T_2}$ $\frac{P_1\times V_1}{T_1}=\frac{P_2\times V_2}{T_2}$

To review the Gas Laws, watch the following video.

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