## Idealized Stirling Cycle

I created a new GeoGebra app based on an ideal Stirling Cycle (A. Romanelli Alternative thermodynamic cycle for the Stirling machine, American Journal of Physics 85, 926 (2017)) which includes two isothermal and two isochoric processes. The Stirling engine is a very good example to apply the First Law of Thermodynamics to, as the amount of

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## PV Diagram for an Ideal Gas

﻿﻿﻿ GeoGebra link: https://www.geogebra.org/m/xyqhfvyw Applying the 1st Law of Thermodynamics to 4 simple changes on an ideal gas, students can check their understanding using this Geogebra app. When is work done positive? Which processes bring about an increase in internal energy or temperature? Which processes require heat input?

## Stirling Engine

I bought a simple beta Stirling engine online at dx.com recently and it came in the mail today. It works well with a cup of hot water placed under it, although it might take a little push to get it started due to the initial static friction. However, once it starts spinning, the wheel goes on

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## Can a Liquid Freeze and Boil Simultaneously?

Witness the freezing and boiling of a liquid take place at the same time. A thorough explanation for this observation is found here.

## Which Equations Apply Only to Ideal Gases?

Students are sometimes unclear about which of the equations taught in the topic of Thermal Physics apply to ideal gases and which apply to all systems (whether ideal or real gas, even liquids and solid). The following table should help to clarify:   Applies to Ideal Gas only Applies to all systems Gas Laws only

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## Adiabatic Process Demonstrations

Here are some interesting lecture demonstrations on adiabatic thermodynamic processes you can carry out. In an adiabatic process, there is no heat transfer between the system and other systems (including its environment.) According to the First Law of Thermodynamics (), where Q = 0, a compression of a gas which is associated with work being done

## P-V diagram simulation

This is an easy-to-use interactive simulation for P-V diagrams, created in GeoGebraTube (not by me!). Students will get to test themselves and familiarise themselves with making quick calculations for simple processes.

## Boyle's Law

Using a hand-operated vacuum pump, we can demonstrate the relationship between pressure and volume of a gas. According to Boyle's law, the pressure of a gas of constant mass and temperature will be inversely proportional to its volume. In our demonstration, we will reduce the ambient pressure within the sealed container, hence allowing the higher

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## Boiling under Reduced Pressure

With the help of a simple manual vacuum pump that is used to keep food fresh, we can demonstrate the effect of a reduced pressure on the boiling point of water. This leads students to a discussion on what it takes to boil a liquid and a deeper understanding of the kinetic model of matter.

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## Egg out of Flask

In a previous demonstration, we put a boiled egg into a flask with a mouth narrower than the egg. The challenge is now to remove the egg from the flask without breaking it. Materials Flask Egg Water Bunsen burner or candle Procedure Pour some water into the conical flask. Invert the flask quickly over a