# IP4 18 Thermal Properties of Matter

## Interactive Heating and Cooling Curves

Heating and cooling curves are graphical representations that show how the temperature of a substance changes as heat is added or removed over time. They illustrate the behavior of substances as they go through different states—solid, liquid, and gas.

Heating Curve: This curve shows how the temperature of a substance increases as it absorbs heat. The curve typically rises as the substance heats up, with plateaus indicating phase changes, where the substance absorbs energy but its temperature remains constant. Check out the heating curves for water and nitrogen using the drop-down menu.

Cooling Curve: This curve is the opposite of the heating curve. It shows how the temperature decreases as the substance loses heat. Like the heating curve, it also has plateaus where phase changes occur, but this time, the substance releases energy. In addition to water, you can also see the cooling curve for ethanol.

With these ChatGPT-generated interactive graphs, users can change the rate of heat input or released from the substance. They can also read the descriptions that explain the changes in the average PE and KE of the molecules during each process.

## Heat capacity and an AI-generated simulation on thermal transfer

This Javascript app will be used in the coming weeks for my IP4 class to demonstrate the effect of heat capacity on the equilibrium temperature of two bodies in thermal contact. When two objects with different temperatures come into contact, heat flows from the hotter object to the cooler one until thermal equilibrium is reached. The heat capacity, which is the amount of heat required to change the temperature of an object per unit change in temperature, plays a crucial role in determining the final equilibrium temperature. Objects with higher heat capacities can absorb more heat without a significant change in temperature, while those with lower heat capacities experience larger temperature changes for the same amount of heat absorbed or released. Thus, the final equilibrium temperature is closer to the initial temperature of the object with the higher heat capacity.

For example, consider a small piece of metal and a large body of water initially at different temperatures. When placed in thermal contact, the metal, with its lower heat capacity, will quickly change temperature as it transfers heat to or absorbs heat from the water. Meanwhile, the water, with its much higher heat capacity, will undergo a relatively smaller temperature change. As a result, the equilibrium temperature will be much closer to the initial temperature of the water.

Prompts given to ChatGPT 4o to create this simulation:

1. Make a javascript simulation showing transfer of heat energy from one body to another. Put all the codes in one file.
2. Show it in a canvas with a height of 100 px and width of 580 px. The first body is hot at first, represented by a red colour body. The second body is cold, represented by blue. The colour of the body should be a function of the temperature. If the temperatures of the two bodies are the same, they should have the same temperature.
3. Use a bold arrow to show the direction of heat transfer.
4. Using plotly.js, create a graph below the canvas that shows the variation of temperature for each body (using red and blue lines) with time.
5. Initialise the graph such that the time axis starts at zero and ends at 5 seconds.
6. Create sliders that can change the heat capacity of each object with a range from 20 to 200 J per degree celsius.

## Thermal Properties of Matter

Made these videos years ago when I was still using an old domain name. Transferred them to the current YouTube channel in 2018. Re-posting them here as I will be using them in class soon – if the live demo fails. The first demonstration never fails to bring excitement to the class and start the lesson with a bang.

## 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.

Materials

1. Vacuum food storage jar with hand-held vacuum pump
2. Hot water

Procedure

1. Boil some water and pour them into the jar such that it is half filled. This is necessary as hand-held vacuum pumps are not able to lower pressure enough for boiling point to drop to room temperature.
2. Cover the jar with the lid and draw out some air with the vacuum pump.

Explanation

When water boils, latent heat is needed to overcome the intermolecular forces of attraction as well as to overcome atmospheric pressure. Atmospheric air molecules would prevent a significant portion of the energetic water molecules from escaping as they will collide with one another, and cause them to return beneath the liquid surface.

Removal of part of the air molecules within the jar lowers the boiling point of water because less energy is needed for molecules to escape the liquid surface.