08 Temperature and Ideal Gases

09 June

Temperature and Pressure of Gas

Seng Kwang Tan 08 Temperature and Ideal Gases, IP4 17 Kinetic Model of Matter, Simulations 0 Comments

This interactive HTML5 simulation models the behavior of gas particles in a fixed-volume container, allowing users to explore the relationships between temperature, pressure, and particle motion. Users can adjust the temperature using a slider, which directly affects the speed of the particles based on kinetic theory. As particles collide with the container walls, they briefly turn red to visually indicate wall interactions—collisions that contribute to pressure. A real-time pressure gauge on the side rises proportionally with temperature, consistent with the ideal gas law.

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500 K

According to the kinetic model of matter, gases consist of a large number of small particles (atoms or molecules) moving randomly and continuously in all directions. These particles have kinetic energy, which depends on temperature.

As temperature increases, the average kinetic energy of the gas particles increases. This means the particles move faster. Since pressure arises from particles colliding with the walls of the container, faster-moving particles collide more frequently and with greater force. These more energetic collisions result in a higher pressure on the container walls.

In a fixed volume, this explains why pressure is directly proportional to temperature (in kelvin), a relationship described by: P∝T
(if volume and number of particles are constant)

12 July

Pressure and Projectile – Penguin’s Poop

Seng Kwang Tan 02 Kinematics, 08 Temperature and Ideal Gases 0 Comments

An interesting paper on the range of penguin’s poop. Their motivation? “Such information is useful for keepers to avoid the direct hitting of faeceses.”

Source: https://arxiv.org/pdf/2007.00926.pdf?fbclid=IwAR2Y6CkFXeCrJH7nxf624To8RcpdRSs0e3_COto9ev6MK-Z_wnObeRHvVlg

27 May

Which Equations Apply Only to Ideal Gases?

Seng Kwang Tan 08 Temperature and Ideal Gases 0 Comments

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 pV=nRT pV≈nRT only for gases at low pressure and high temperatures
Average Kinetic Energy $$=\dfrac{3}{2}kT$$ $$\propto T$$
Internal Energy U = sum of KE of molecules
U=32NkT=32nRT=32pV		 U = sum of KE and PE of molecules
First Law of Thermodynamics applies to all systems ΔU=Q+W
01 June

Boyle’s Law

Seng Kwang Tan 08 Temperature and Ideal Gases, Demonstrations

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 internal pressure of a balloon to cause it to expand. When the volume within the balloon increases, the internal pressure can be observed to decrease until it is in equilibrium with the surrounding pressure.

While the relationship between pressure and volume is not exactly obeying Boyle’s law due to additional factors such as the tension due to the elastic property of the balloon, it does demonstrate an inverse relationship.

30 March

Boiling under Reduced Pressure

Seng Kwang Tan 08 Temperature and Ideal Gases, Demonstrations, IP4 18 Thermal Properties of Matter

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.

29 March

Egg out of Flask

Seng Kwang Tan 08 Temperature and Ideal Gases, Demonstrations, IP3 05 Density and Pressure

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

  1. Flask
  2. Egg
  3. Water
  4. Bunsen burner or candle

Procedure

  1. Pour some water into the conical flask.
  2. Invert the flask quickly over a tray such that the egg seals the mouth of the flask, preventing the water from coming out.
  3. Light a flame and place the part of the flask with water over the flame. This will help prevent the heat from cracking the flask.
  4. Place a tray under the mouth of the flask as the egg slides out to prevent a mess.

Explanation

The flame heats up the air and the water in the flask. The heated air expands while some of the water vapourizes. With the increase in amount of gas and temperature, the pressure within the flask increases.