OCR A-Level Physics B H557
Planning
Implementing
Analysis
Evaluation
Practical Skills
Use of Apparatus and Techniques
Fundamental Data Analysis
Imaging and Signalling
Sensing
Mechanical Properties of Materials
Waves and Quantum Behaviour
Space, Time and Motion
Creating Models
Out Into Space
Our Place in the Universe
Matter: Very Simple
Matter: Hot or Cold
Electromagnetism
Charge and Field
Probing Deep Into Matter
Ionising Radiation and Risk
Matter: Very Simple
Temperature, average energy per particle and internal energy
- 3 things to know
- Components 01, 02 and 03
Overview
Recall questions on a particle's mean kinetic energy, kT as a rough measure, its value in joules and electronvolts, the internal energy of an ideal gas, and root mean square speeds.
What you need to know
Answer each one before you reveal it.
Why is kT often used as a rough measure of the energy per particle?
Calculate the value of kT at 300 K.
Questions from this subtopic
Each one with the model answer underneath.
- 1
How is the absolute temperature of a gas related to the energy of its particles?
Model answer
The average random kinetic energy of a particle is directly proportional to the absolute temperature.
- 2
Give the expression for the mean kinetic energy of a particle in an ideal gas.
Model answer
It is 3/2 kT, where k is the Boltzmann constant and T the absolute temperature.
- 3
Why is kT often used as a rough measure of the energy per particle?
Model answer
The factor of 3/2 is close to one, so kT gives the right order of magnitude and is good enough for an estimate.
- 4
Calculate the value of kT at 300 K.
Model answer
kT = 1.38 × 10⁻²³ × 300 = 4.1 × 10⁻²¹ J.
- 5
Express the value of kT at 300 K in electronvolts.
Model answer
It is 4.14 × 10⁻²¹ ÷ (1.60 × 10⁻¹⁹) ≈ 0.026 eV, about one fortieth of an electronvolt.
- 6
Calculate the mean kinetic energy of a gas particle at 300 K.
Model answer
It is 3/2 kT = 1.5 × 1.38 × 10⁻²³ × 300 = 6.2 × 10⁻²¹ J.
Other ways to work this
The same content, four other ways.
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