# Unit Planner: Thermodynamics Unit: Thermodynamics

Start date:

End date:

Diploma assessment

When will the content be assessed?

Paper 1
Paper 2
Paper 3 x
Investigation x

Text book reference

Hamper - online resources

#### Inquiry: Establishing the purpose of the unit

Transfer Goals
List here one to three big, overarching, long-term goals for this unit. Transfer goals are the major goals that ask students to “transfer”, or apply, their knowledge, skills, and concepts at the end of the unit under new/different circumstances, and on their own without scaffolding from the teacher.

• To know the definitions of isobaric, isothermic, isovolumetric and adiabatic process
• To understand the implications of the first and second laws of thermodynamics for energy changes in system
• To be able to represent engine cycles on P-V diagrams

Content
List here the key content that students will know by the end of the unit

Energy and ideal gas transformations

• Introduce the idea of using a gas to model a thermal system.
• Revise the properties of an ideal gas and the ideal gas equation.
• Introduce the way energy changes when a gas is transformed.

First law of thermodynamics

• Define thermal efficiency η = W/QH and derive η = 1 - QC/QH

Second law of thermodynamics

• State the 2nd law of thermodynamics in terms of the spreading out of energy.
• Define entropy and understand its connection to the degradation of energy.
• State the 2nd law in terms of entropy.

Skills
List here the key skills that students will develop by the end of the unit.

Energy and ideal gas transformations

• See how constant volume, pressure and temperature transformations can be represented on a PV diagram.

First law of thermodynamics

• Apply the law of conservation of energy to a thermal system to derive the 1st law of thermodynamics.
• Apply the 1st law to constant volume, pressure, temp and adiabatic processes.
• Apply the formula PV5/3= constant to calculate the new pressure after an adiabatic process.

Second law of thermodynamics

• Apply the 1st law to each stage of the Carnot cycle.
• Apply the 1st law to the reverse Carnot cycle.

Concepts
List here the key concepts that students will understand by the end of the unit

Energy and ideal gas transformations

• Understand how the states of a gas can be represented on a PV diagram.

First law of thermodynamics

• Understand the relationship between the PV diagram and energy changes.
• Understand what is meant by a cycle.
• Understand how to use a PV diagram to represent a cycle and use it to analyse the stages.
• Understand the principle of a heat engine and how it is represented on a PV diagram.

Second law of thermodynamics

• Understand why a heat engine needs to lose heat so that the work done by the gas is more than the work done on the gas.
• Understand why work needs to be done to move thermal energy from a cold source to a hot one.
• Understand why energy always tends to spread out.
• Understand why an isothermal process is impossible.
• Understand why the 2nd law implies that an engine can not be 100% efficient.

Applications
Examples of real world practical applications of knowledge.

• Engines! However, it is not easy to explain more complex engines in terms of a PV graph since the mass of gas doesn't stay constant.
• Some nice animations here.

#### Action: teaching and learning through Inquiry

Approaches to teaching
Tick boxes to indicate pedagogical approaches used.

Lecture x
Simulation x
Small group work (pairs) x
Hands on practical x
Video x
Student centred inquiry x

TOK
Examples of how TOK can be introduced in this unit

• Yet another example of how graphs are used to help us visualise something that we can't see.
• Students often say that they understand the bouncing balls but not the gas, or that they can understand the graph but can't see what is actually happening. Is it enough to understand the model without knowing what really happens?
• The 2nd law has been used to explain many things from the breakdown of law and order to the existence of God. Is it right to apply a physical law to non physical things?
• Probability says that there is a small possibility that all the molecules of air in a room could randomly end up in the corner and we would all die. This would however be against the 2nd law (unless entropy increased somewhere else). If maths says something should happen is that the truth?

NOS
Examples of how NOS can be introduced in this unit.

• Describing how the molecules of a gas move when the gas is transformed is very complicated but saying how energy changes isn't. Conservation of energy can be used to give a simpler model of a physical system.
• The history of thermodynamics is an interesting example of the way scientific theories develop. Carnot developed the theory of the heat engine based on the transfer of a weightless invisible fluid.
• The second law is one of the NOS examples given in the subject guide showing how different perspectives lead to different statements of the same law.

Assessments
Tests, exams and marked labs

Worksheets and exercises

Resources
Video clips, simulations demonstrations etc.

#### Reflections

What went well
List the portions of the unit (content, assessment, planning) that were successful

What didn’t work well
List the portions of the unit (content, assessment, planning) that were not as successful as hoped

Notes/changes/suggestions:
List any notes, suggestions, or considerations for the future teaching of this unit.

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