Define internal energy .

Internal energy is the sum of the kinetic and potential energies of all the molecules within a given mass of a substance.

What is the kinetic energy of the molecules in a substance due to, and what does it determine?

It is due to the speed of the molecules, and it determines the substance's temperature .

What is the potential energy of the molecules in a substance due to?

The separation between the molecules and their position within the structure. Greater intermolecular forces give a higher potential energy.

List four factors that determine the internal energy of a system.

Temperature Random motion of the molecules The phase of matter (gases highest, solids lowest) Intermolecular forces between the particles

The internal energy of a system can decrease by losing heat to its surroundings or by .......... state from a gas to a liquid or a liquid to a solid.

The internal energy of a system can decrease by losing heat to its surroundings or by changing state from a gas to a liquid or a liquid to a solid.

True or False? The kinetic energy of an egg thrown through the air is part of its internal energy.

False. Internal energy relates only to the random internal motion of a substance's molecules, not the overall macroscopic movement of the object as a whole.

Define absolute zero .

Absolute zero is the lowest temperature possible, equal to 0 K or -273.15 °C. It is the temperature at which the molecules in a substance have zero kinetic energy .

Why does a temperature change of 1 K equal a temperature change of 1 °C?

The divisions on the Kelvin and Celsius scales are the same size, so a temperature difference (Δθ) is identical whichever unit it is measured in.

According to kinetic theory, what happens to the molecules of a solid when it is heated?

They receive the energy as kinetic energy and vibrate faster .

Absolute zero is the theoretical temperature at which the molecules of a substance have .......... kinetic energy.

Absolute zero is the theoretical temperature at which the molecules of a substance have zero kinetic energy.

True or False? Absolute zero has been achieved in a laboratory.

False. Absolute zero remains a theoretical point that has never actually been achieved by scientists in a laboratory.

The Boltzmann constant relates the microscopic properties of particles, such as their kinetic energy, to their .......... properties, such as temperature.

The Boltzmann constant relates the microscopic properties of particles, such as their kinetic energy, to their macroscopic properties, such as temperature.

True or False? Doubling the pressure on a fixed mass of ideal gas at constant temperature will double its volume.

False. By Boyle's law , pressure is inversely proportional to volume at constant temperature, so doubling the pressure halves the volume.

In the Boyle's law experiment, what are the independent and dependent variables?

Independent variable: mass added to the plunger, m Dependent variable: volume of trapped gas, V

Name two variables that must be controlled in this experiment.

Temperature Cross-sectional area of the syringe

How is the actual pressure of the trapped gas found from the pressure exerted by the masses?

Pressure of the gas = atmospheric pressure − exerted pressure from the masses

What graph is plotted to confirm Boyle's law, and what result confirms it?

A graph of p against 1/ V is plotted. A straight line through the origin confirms that pV = constant.

Before taking each volume reading, you should wait a few seconds after adding the mass to allow the .......... to equilibrate.

Before taking each volume reading, you should wait a few seconds after adding the mass to allow the temperature to equilibrate.

True or False? Friction in the syringe is a random error in this experiment.

False. Friction in the syringe causes a systematic error , not a random one.

c rms ( root mean square speed ) is the square root of the mean of the squares of the speeds of all the molecules in a gas.

Equating pV = NkT with the kinetic theory pressure equation and simplifying gives m ( c rms ) 2 = .......... kT .

Equating pV = NkT with the kinetic theory pressure equation and simplifying gives m ( c rms ) 2 = 3 kT .

International A Level (IAL)PhysicsEdexcelFlashcards5. Thermodynamics, Radiation, Oscillations & CosmologyKinetic Theory & Ideal Gases

Kinetic Theory & Ideal Gases (Edexcel International A Level (IAL) Physics): Flashcards

Exam code: YPH11

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FrontInternal Energy
Define internal energy.

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Cards in this collection (31)

Define internal energy.
Internal energy is the sum of the kinetic and potential energies of all the molecules within a given mass of a substance.
What is the kinetic energy of the molecules in a substance due to, and what does it determine?
It is due to the speed of the molecules, and it determines the substance's temperature.
What is the potential energy of the molecules in a substance due to?
The separation between the molecules and their position within the structure. Greater intermolecular forces give a higher potential energy.
List four factors that determine the internal energy of a system.
- Temperature
- Random motion of the molecules
- The phase of matter (gases highest, solids lowest)
- Intermolecular forces between the particles
The internal energy of a system can decrease by losing heat to its surroundings or by .......... state from a gas to a liquid or a liquid to a solid.
The internal energy of a system can decrease by losing heat to its surroundings or by changing state from a gas to a liquid or a liquid to a solid.
True or False?
The kinetic energy of an egg thrown through the air is part of its internal energy.
False.
Internal energy relates only to the random internal motion of a substance's molecules, not the overall macroscopic movement of the object as a whole.
Define absolute zero.
Absolute zero is the lowest temperature possible, equal to 0 K or -273.15 °C. It is the temperature at which the molecules in a substance have zero kinetic energy.
Convert a temperature of 300 K into degrees Celsius.
$θ / °C = T / K - 273.15$
$300 - 273.15 = 26.85 °C$
Why does a temperature change of 1 K equal a temperature change of 1 °C?
The divisions on the Kelvin and Celsius scales are the same size, so a temperature difference (Δθ) is identical whichever unit it is measured in.
According to kinetic theory, what happens to the molecules of a solid when it is heated?
They receive the energy as kinetic energy and vibrate faster.
Absolute zero is the theoretical temperature at which the molecules of a substance have .......... kinetic energy.
Absolute zero is the theoretical temperature at which the molecules of a substance have zero kinetic energy.
True or False?
Absolute zero has been achieved in a laboratory.
False.
Absolute zero remains a theoretical point that has never actually been achieved by scientists in a laboratory.
Define Boyle's law.
For a fixed mass of gas at constant temperature, the pressure is inversely proportional to the volume: $P_{1} V_{1} = P_{2} V_{2}$
State Charles's law.
For a fixed mass of gas at constant pressure, the volume is directly proportional to the thermodynamic temperature: $\frac{V_{1}}{T_{1}} = \frac{V_{2}}{T_{2}}$
State the pressure law.
For a fixed mass of gas at constant volume, the pressure is directly proportional to the thermodynamic temperature: $\frac{P_{1}}{T_{1}} = \frac{P_{2}}{T_{2}}$
Write the ideal gas equation in terms of the number of molecules, N, and the Boltzmann constant, k.
$p V = N k T$
The Boltzmann constant relates the microscopic properties of particles, such as their kinetic energy, to their .......... properties, such as temperature.
The Boltzmann constant relates the microscopic properties of particles, such as their kinetic energy, to their macroscopic properties, such as temperature.
True or False?
Doubling the pressure on a fixed mass of ideal gas at constant temperature will double its volume.
False.
By Boyle's law, pressure is inversely proportional to volume at constant temperature, so doubling the pressure halves the volume.
In the Boyle's law experiment, what are the independent and dependent variables?
- Independent variable: mass added to the plunger, m
- Dependent variable: volume of trapped gas, V
Name two variables that must be controlled in this experiment.
- Temperature
- Cross-sectional area of the syringe
How is the pressure exerted by the added masses calculated?
$P = \frac{F}{A} = \frac{m g}{A}$
where A is the cross-sectional area of the syringe.
How is the actual pressure of the trapped gas found from the pressure exerted by the masses?
Pressure of the gas = atmospheric pressure − exerted pressure from the masses
What graph is plotted to confirm Boyle's law, and what result confirms it?
A graph of p against 1/V is plotted. A straight line through the origin confirms that pV = constant.
Before taking each volume reading, you should wait a few seconds after adding the mass to allow the .......... to equilibrate.
Before taking each volume reading, you should wait a few seconds after adding the mass to allow the temperature to equilibrate.
True or False?
Friction in the syringe is a random error in this experiment.
False.
Friction in the syringe causes a systematic error, not a random one.
State the equation for the average kinetic energy of one molecule of an ideal gas in terms of the Boltzmann constant.
$E_{k} = \frac{3}{2} k T$
What is the relationship between the mean kinetic energy of an ideal gas molecule and its thermodynamic temperature?
They are directly proportional: $E_{k} \propto T$
Write the average molecular kinetic energy equation in terms of the molar gas constant R and Avogadro's constant N_A (instead of k).
$E_{k} = \frac{3}{2} (\frac{R}{N_{A}}) T$
Define c_rms.
c_rms (root mean square speed) is the square root of the mean of the squares of the speeds of all the molecules in a gas.
Equating pV = NkT with the kinetic theory pressure equation and simplifying gives m(c_rms)² = .......... kT.
Equating pV = NkT with the kinetic theory pressure equation and simplifying gives m(c_rms)² = 3 kT.
True or False?
If the thermodynamic temperature of an ideal gas doubles, the average kinetic energy of its molecules doubles.
True.
Since $E_{k} \propto T$ , doubling the thermodynamic temperature doubles the average molecular kinetic energy.

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