3. Thermal physics

3. Thermal physics

3.1 – Thermal concepts

Nature of science:

  • Evidence through experimentation: Scientists from the 17th and 18th centuries were working without the knowledge of atomic structure and sometimes developed theories that were later found to be incorrect, such as phlogiston and perpetual motion capabilities. Our current understanding relies on statistical mechanics providing a basis for our use and understanding of energy transfer in science.

Understandings:

  • Molecular theory of solids, liquids and gases

  • Temperature and absolute temperature

  • Internal energy

  • Specific heat capacity

  • Phase change

  • Specific latent heat

Applications and skills:

  • Describing temperature change in terms of internal energy

  • Using Kelvin and Celsius temperature scales and converting between them

  • Applying the calorimetric techniques of specific heat capacity or specific latent heat experimentally

  • Describing phase change in terms of molecular behaviour

  • Sketching and interpreting phase change graphs

  • Calculating energy changes involving specific heat capacity and specific latent heat of fusion and vaporization

3.2 – Modelling a gas

Nature of science:

  • Collaboration: Scientists in the 19th century made valuable progress on the modern theories that form the basis of thermodynamics, making important links with other sciences, especially chemistry. The scientific method was in evidence with contrasting but complementary statements of some laws derived by different scientists. Empirical and theoretical thinking both have their place in science and this is evident in the comparison between the unattainable ideal gas and real gases.

Understandings:

  • Pressure

  • Equation of state for an ideal gas

  • Kinetic model of an ideal gas

  • Mole, molar mass and the Avogadro constant

  • Differences between real and ideal gases

Applications and skills:

  • Solving problems using the equation of state for an ideal gas and gas laws

  • Sketching and interpreting changes of state of an ideal gas on pressure–volume, pressure–temperature and volume–temperature diagrams

  • Investigating at least one gas law experimentally

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