The variables kept constant in Charles’ law are:
A volume and temperature
B amount of gas and pressure
C amount of gas and temperature
D pressure and volume
The correct answer and explanation is:
Correct Answer: C. amount of gas and pressure
Explanation (300 words):
Charles’ Law is one of the fundamental gas laws that describe the relationship between temperature and volume of a gas under specific conditions. This law is named after the French scientist Jacques Charles, who first formulated it in the late 18th century.
Charles’ Law states:
At constant pressure and constant amount of gas, the volume of a gas is directly proportional to its absolute temperature (measured in Kelvin).
Mathematically, this is expressed as: V1T1=V2T2\frac{V_1}{T_1} = \frac{V_2}{T_2}
Where:
- V1V_1 and V2V_2 are the initial and final volumes,
- T1T_1 and T2T_2 are the initial and final temperatures (in Kelvin).
What variables are held constant in Charles’ Law?
The law holds pressure and the amount of gas (i.e., the number of moles) constant.
This means:
- Pressure does not change; the gas is allowed to expand or contract freely without altering the pressure.
- Amount of gas remains fixed; there is no addition or removal of gas particles.
As a result, when the temperature increases, the gas particles move faster and spread further apart, increasing volume. Conversely, when the temperature decreases, particle movement slows, and the volume decreases.
Other options clarified:
- A. Volume and temperature: These are the changing variables, not constant.
- B. Amount of gas and pressure: This is the correct pair that remains constant.
- D. Pressure and volume: These are held constant in Gay-Lussac’s Law, not Charles’ Law.
Conclusion:
In Charles’ Law, the amount of gas and pressure are kept constant while examining the relationship between volume and temperature.