Objective: The aim of this practical investigation is to determine the value of zero Kelvin, also known as absolute zero, by extrapolating the relationship between temperature and volume for an ideal gas under constant pressure.
Background: Charles’s Law states that the volume of an ideal gas is directly proportional to its temperature, as long as the pressure remains constant. Mathematically, this can be represented as:
V ∝ T or V = kT
where V is the volume of the gas, T is the temperature in Kelvin, and k is the proportionality constant.
By plotting the volume of the gas against its temperature, we can obtain a straight line, which, when extrapolated to the temperature axis, will give the value of absolute zero.
Materials:
- A syringe or a gas burette
- A rubber stopper or a bung with a small hole
- A pressure sensor (optional if constant pressure is to be maintained)
- A temperature sensor (preferably a digital thermometer)
- A beaker or container
- Ice, room temperature water, and hot water
- A retort stand with a clamp
- A laptop or graphing calculator (for plotting and extrapolating the graph)
- A lab coat and safety goggles
Procedure:
- Set up the syringe or gas burette on the retort stand using the clamp, ensuring that the syringe is vertical and can move freely.
- Seal the syringe or burette with the rubber stopper or bung to create a closed system.
- Fill the beaker or container with ice and water to create an ice bath. Record the temperature of the ice bath using the temperature sensor. Ensure the temperature remains constant throughout the experiment.
- Immerse the syringe or burette into the ice bath, allowing the gas inside to cool down. Wait for 5-10 minutes to ensure that the gas has reached thermal equilibrium with the ice bath.
- Record the volume of the gas at this temperature. If you are using a pressure sensor, make sure the pressure remains constant throughout the experiment.
- Repeat steps 3-5 with room temperature water and hot water, ensuring that the temperatures of the water baths remain constant.
- Using a laptop or graphing calculator, plot a graph of the volume of the gas (y-axis) against the temperature in Kelvin (x-axis).
- Draw a line of best fit through the data points and extrapolate this line to the temperature axis. The point at which the line intersects the temperature axis will give the value of zero Kelvin.
- Record the value of absolute zero obtained from the graph.
- Compare the experimental value of absolute zero with the accepted value (-273.15°C or 0 K) and calculate the percentage error.
Safety Precautions:
- Wear a lab coat and safety goggles throughout the experiment to protect against potential spills or splashes.
- Handle the hot water carefully to avoid burns.
- If using a pressure sensor, ensure that the pressure remains constant throughout the experiment. If the pressure increases, release some gas from the syringe or burette to prevent it from bursting.
Determining the Value of Zero Kelvin through Extrapolation of Charles’s Law
Objective: The aim of this practical investigation is to determine the value of zero Kelvin, also known as absolute zero, by extrapolating the relationship between temperature and volume for an ideal gas under constant pressure.
Background: Charles’s Law states that the volume of an ideal gas is directly proportional to its temperature, as long as the pressure remains constant. Mathematically, this can be represented as:
V ∝ T or V = kT
where V is the volume of the gas, T is the temperature in Kelvin, and k is the proportionality constant.
By plotting the volume of the gas against its temperature, we can obtain a straight line, which, when extrapolated to the temperature axis, will give the value of absolute zero.
Materials:
- A syringe or a gas burette
- A rubber stopper or a bung with a small hole
- A pressure sensor (optional, if constant pressure is to be maintained)
- A temperature sensor (preferably a digital thermometer)
- A beaker or container
- Ice, room temperature water, and hot water
- A retort stand with a clamp
- A laptop or graphing calculator (for plotting and extrapolating the graph)
- A lab coat and safety goggles
Procedure:
- Set up the syringe or gas burette on the retort stand using the clamp, ensuring that the syringe is vertical and can move freely.
- Seal the syringe or burette with the rubber stopper or bung to create a closed system.
- Fill the beaker or container with ice and water to create an ice bath. Record the temperature of the ice bath using the temperature sensor. Ensure the temperature remains constant throughout the experiment.
- Immerse the syringe or burette into the ice bath, allowing the gas inside to cool down. Wait for 5-10 minutes to ensure that the gas has reached thermal equilibrium with the ice bath.
- Record the volume of the gas at this temperature. If you are using a pressure sensor, make sure the pressure remains constant throughout the experiment.
- Repeat steps 3-5 with room temperature water and hot water, ensuring that the temperatures of the water baths remain constant.
- Using a laptop or graphing calculator, plot a graph of the volume of the gas (y-axis) against the temperature in Kelvin (x-axis).
- Draw a line of best fit through the data points and extrapolate this line to the temperature axis. The point at which the line intersects the temperature axis will give the value of zero Kelvin.
- Record the value of absolute zero obtained from the graph.
- Compare the experimental value of absolute zero with the accepted value (-273.15°C or 0 K) and calculate the percentage error.
Safety Precautions:
- Wear a lab coat and safety goggles throughout the experiment to protect against potential spills or splashes.
- Handle the hot water carefully to avoid burns.
- If using a pressure sensor, ensure that the pressure remains constant throughout the experiment. If the pressure increases, release some gas from the syringe or burette to prevent it from bursting.
Practical Science 