Chemistry 12: Charles's Law

Chemistry 12: Gas Laws Charles's Law

Physical Science Safety Guidelines

Chemistry Safety

Jacques Charles

Ideal gases

Prior Knowledge/Preview

Units of temperature

Celsius and Kelvin (we won't use Fahrenheit here)

VIDEO on Charles's Law Lab with data

Aerospace CONNECTIONS:

Gas Laws in aerospace

Applications and examples:

Fuels--temperatures

Breathing in Space--volume/temperature in a space capsule

Temperature changes in Space

Temperature and Altitude

In the Gas Laws, we are investigating the relationships between P, V and T

Start by studying the relationship between TWO variables at a time and keeping the third constant as well as the amount (# moles) of gas

What is kept constant?

Charles’s Law

Investigating the relationship between volume and temperature of a gas--providing this pressure remains constant and the amount of gas (number of moles)

Describe what's happening to the particles in the balloon

Describe what is happening to the particles in the two balloons below

Explain WHY

Charles's Law Lab

Data collection activity:

SAFETY: Wear goggles and lab coat/apron

Care with hot objects

Method 1

Using the apparatus to the right, you will take the temperature and note the DIAMETER of the balloon for five trials at different temperatures

Do Trial #2 first when you do the actual lab--at room temperature

Then immerse the beaker in a "freezing" solution of ice, a small amount of water and salt to get the lowest temperature in your trials.

Measure the diameter carefully each time

Make a results table and add the data as you collect it from the trials here. If you are doing the lab you will need to add observations for your qualitative data

Use a hot plate to heat the water in the beaker--CARE with hot objects including at the end of the lab when the hotplate remains hot for some time after turning off.

Again note the data for these higher temperature trials

Charles's Law Lab

Analyzing data

Looking at your data table, do you see any trends in the results obtained?

Draw a graph--BUT in an interesting way!

Just use the top right-hand portion of the graph paper

PLOT volume of balloon in cm^3 versus temperature in degrees Celsius

To calculate the volume, use the formula

BUT REMEMBER to us radius--you measured diameter. Why were you asked to measure the diameter, not the radius?

What is the shape of the graph?

If it's a straight line there is a relationship y = mx + b

If it goes through the origin, x is directly proportional to y: y x or y = constant times x

To get your graph to go through the "origin", extrapolate (extend) the line of the graph, so that it goes through the x axis.

Extend the scale of your graph backwards to get your experimental value of ABSOLUTE ZERO--the temperature where the gas has no volume . . .

So volume IS PROPORTIONAL to temperature--but only proportional to the absolute temperature when measured in Kelvin

Charles's Law Method 2

Here you have a thin glass tube--a melting point tube. Your teacher will prepare these with some concentrated sulfuric acid in the middle of the tube.

CARE corrosive liquid and glass--goggles and gloves and apron/lab coat

Take the temperature of the water surrounding the tube, the height of the air trapped

Change the temperature 5 or 6 times and note the height of the air column each time

Draw a graph of your results--again drawing the height versus temperature in degrees Celsius on a quarter-sized sheet and extrapolating to get the value of absolute zero