Teacher instructions

Work through this resource material in the following sequence:

20 minutes

Tune in: What will change?

20 minutes

Find out: Experiment time!

20 minutes

Reflection: What did we learn?

Tune in: What will change?

Step 1.

We want to prime students to move away from the misconception that gas, especially air, is a big 'nothingness'. Solids and liquids we can see and hold, so we know that they are there, but it can be harder for students to comprehend a gas.

Lead students through the following discussion:

does gas take up space? You might want to use your balloon to demonstrate to students that yes, gas does take up space. At first the balloon is empty, then, by blowing into it, it fills with a certain volume of gas.
do gases have weight? That is, if we put a certain amount of a gas in a container and put that container on some scales, would it have a weight (beyond that of the container). Some students might even be able to discuss how some gases are denser and therefore weigh more per volume than other gases, especially air.
is there space in between gas? That is, if we wave our hand in the air, are we moving between blobs of air and spots of nothingness? Or is it all air? This can be a difficult concept for students to understand, so we're going to conduct an experiment to prove it.

Step 2.

Explain the experiment to your students.

Step 3.

Students write their predictions in the first section of the Student Worksheet.

Find out: Experiment time!

Step 1.

Peel the hard-boiled egg.

Step 2.

Light one end of your strip of paper and drop it carefully into the bottle.

Step 3.

Place your egg over the opening of the bottle, skinny end down.

Step 4.

Watch the egg be sucked into the bottle!

Reflection: What did we learn?

As we demonstrated with the balloon, there is a gas within the bottle. Putting the egg on top of the bottle acts like a seal, locking in a certain amount of gas.

However, there is also a lot of free space within the bottle. Don't call it empty space, as it's not nothing.

We first need students to understand that solids, liquids and gases are all made up of particles. Particles are the tiny units of matter that make up all of the substances around us, including solids, liquids, and gases. Students might think that everything, especially liquids and gases, are big blobs of 'stuff', but that's not quite the case.

In a solid, the particles are tightly packed together and arranged in a regular pattern, which gives solids a definite shape and volume. The particles in a solid are held together by strong attractive forces, which limit their movement to a small amount of vibration around their fixed positions.

In a liquid, the particles are still connected by attractive forces, though those bonds are not as strong. This allows the particles in a liquid are able to move past each other, which allows liquids to take on the shape of their container. However, liquids still have a definite volume because the particles are still in close proximity to each other. We are able to see that we can break the bonds of a liquid because, if we stretch a little pool of water too far, it splits into two smaller pools.

In a gas, the particles are far apart and very, very loosely attracted to one another. The particles in a gas are moving rapidly and in random directions, independent of one another. So, while we might see a 'cloud' of gas, this is actually lots of little particles of gas all sort of within the same spot.

When he gas is within a container, such as a bottle or a balloon, the molecules collide with the walls of the container and create a force that is exerted on the walls. This force is known as the pressure of the gas.

Because the gas within and without the bottle is the same (oxygen), roughly the same amount of particles are bouncing off the inside and outside the bottle.

However, when we put the match in the bottle, the oxygen is burned and becomes carbon dioxide.

Carbon dioxide is less dense than oxygen because it has fewer particles. This means more molecules are hitting the outside of the bottle than the inside.

When the egg is placed on top, the high-pressure oxygen wants to rush into the low-pressure inside of the bottle, which is called a vacuum. In trying to get in, the forces are so strong they just push the egg into the bottle along with the air.

Experiment - What is Air Pressure?

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