The Heat Added to the System

Oct 13, 2025 by wbrum.org 20 views

The first law of thermodynamics is a fundamental principle in physics that describes the relationship between heat, work, and energy. It states that the change in internal energy of a system is equal to the heat added to the system minus the work done by the system. Mathematically, this can be expressed as:

ΔE = Q - W

where ΔE is the change in internal energy, Q is the heat added to the system, and W is the work done by the system.

The Ideal Gas Law

The ideal gas law is a fundamental equation in physics that describes the behavior of ideal gases. It states that the product of the pressure, volume, and number of moles of a gas is equal to the product of the gas constant and the temperature. Mathematically, this can be expressed as:

PV = nRT

where P is the pressure, V is the volume, n is the number of moles, R is the gas constant, and T is the temperature.

The Monatomic Gas

A diatomic gas is a type of gas that consists of molecules with two atoms. The specific heat capacity of a diatomic gas is given by:

Cv = (5/2)R

where Cv is the specific heat capacity at constant volume, and R is the gas constant.

The Work Done by the Gas

The work done by the gas can be calculated using the formula:

W = PΔV

where W is the work done, P is the pressure, and ΔV is the change in volume.

The Heat Added to the System

The heat added to the system can be calculated using the formula:

Q = nCpΔT

where Q is the heat added, n is the number of moles, Cp is the specific heat capacity at constant pressure, and ΔT is the change in temperature.

The Change in Internal Energy

The change in internal energy can be calculated using the formula:

ΔE = Q - W

where ΔE is the change in internal energy, Q is the heat added, and W is the work done.

The Temperature Change

The temperature change can be calculated using the formula:

ΔT = (Q - W) / (nCv)

where ΔT is the change in temperature, Q is the heat added, W is the work done, n is the number of moles, and Cv is the specific heat capacity at constant volume.

Calculating the Change in Temperature

Given that the piston contains 3.77 mol of a diatomic gas, the gas does 222 J of work while 435 J of heat are added, we can calculate the change in temperature using the formula:

ΔT = (Q - W) / (nCv)

First, we need to calculate the specific heat capacity at constant volume (Cv) for the diatomic gas:

Cv = (5/2)R

where R is the gas constant.

The gas constant (R) is approximately 8.314 J/mol·K.

Cv = (5/2) × 8.314 J/mol·K = 20.785 J/mol·K

Next, we can calculate the change in internal energy (ΔE):

ΔE = Q - W = 435 J - 222 J = 213 J

Now, we can calculate the change in temperature (ΔT):

ΔT = ΔE / (nCv) = 213 J / (3.77 mol × 20.785 J/mol·K) = 2.73 K

To convert the change in temperature from Kelvin to Celsius, we can use the formula:

ΔT (°C) = ΔT (K) - 273.15

ΔT (°C) = 2.73 K - 273.15 = -270.42 °C

Therefore, the change in temperature is approximately -270.42 °C.

Conclusion

Q: What is the first law of thermodynamics?

A: The first law of thermodynamics is a fundamental principle in physics that describes the relationship between heat, work, and energy. It states that the change in internal energy of a system is equal to the heat added to the system minus the work done by the system.

Q: What is the ideal gas law?

A: The ideal gas law is a fundamental equation in physics that describes the behavior of ideal gases. It states that the product of the pressure, volume, and number of moles of a gas is equal to the product of the gas constant and the temperature.

Q: What is the specific heat capacity of a diatomic gas?

A: The specific heat capacity of a diatomic gas is given by:

Cv = (5/2)R

where Cv is the specific heat capacity at constant volume, and R is the gas constant.

Q: How is the work done by a gas calculated?

A: The work done by a gas can be calculated using the formula:

W = PΔV

where W is the work done, P is the pressure, and ΔV is the change in volume.

Q: How is the heat added to a system calculated?

A: The heat added to a system can be calculated using the formula:

Q = nCpΔT

where Q is the heat added, n is the number of moles, Cp is the specific heat capacity at constant pressure, and ΔT is the change in temperature.

Q: How is the change in internal energy calculated?

A: The change in internal energy can be calculated using the formula:

ΔE = Q - W

where ΔE is the change in internal energy, Q is the heat added, and W is the work done.

Q: How is the temperature change calculated?

A: The temperature change can be calculated using the formula:

ΔT = (Q - W) / (nCv)

where ΔT is the change in temperature, Q is the heat added, W is the work done, n is the number of moles, and Cv is the specific heat capacity at constant volume.

Q: What is the gas constant (R)?

A: The gas constant (R) is approximately 8.314 J/mol·K.

Q: What is the specific heat capacity at constant pressure (Cp) for a diatomic gas?

A: The specific heat capacity at constant pressure (Cp) for a diatomic gas is given by:

Cp = (7/2)R

where Cp is the specific heat capacity at constant pressure, and R is the gas constant.

Q: How is the change in temperature calculated for a diatomic gas?

A: The change in temperature can be calculated using the formula:

ΔT = (Q - W) / (nCv)

where ΔT is the change in temperature, Q is the heat added, W is the work done, n is the number of moles, and Cv is the specific heat capacity at constant volume.

Q: What is the change in temperature for a diatomic gas that expands as it does 222 J of work while 435 J of heat are added?

A: The change in temperature for a diatomic gas that expands as it does 222 J of work while 435 J of heat are added is approximately -270.42 °C.

Q: What is the significance of the first law of thermodynamics?

A: The first law of thermodynamics is a fundamental principle in physics that describes the relationship between heat, work, and energy. It has numerous applications in various fields, including engineering, chemistry, and biology.

Q: What is the ideal gas law used for?

A: The ideal gas law is used to describe the behavior of ideal gases and to calculate the properties of gases, such as pressure, volume, and temperature.

Q: What is the specific heat capacity used for?

A: The specific heat capacity is used to calculate the amount of heat energy required to change the temperature of a substance by a given amount.

Q: What is the change in internal energy used for?

A: The change in internal energy is used to calculate the change in the total energy of a system, including the kinetic energy of the particles and the potential energy of the system.

Q: What is the temperature change used for?

A: The temperature change is used to calculate the change in the temperature of a system, which is an important parameter in many physical and chemical processes.