Science Projects for Eighth Grade: Experimenting with Pressure Using a Marshmallow

Lesson:

This experiment can be used when studying pressure and it's effect on objects.

Teach:

Pressure can be observed when air is added to a space or when air is taken out of a space. This experiment will demonstrate both using a glass jar and a marshmallow.

Materials:

1. Marshmallow
2. Pickle jar
3. Straw
4. Play dough
5. Nail
6. Hammer
7. Notebooks
8. Pencils

Procedure:

1. Have a student volunteer take the metal lid off of the pickle jar. Make sure the pickle jar has been cleaned and dried ahead of time.
2. Use a nail and a hammer to put a hole in the middle of the pickle jar lid. Make sure the hole is

   large enough for the straw to fit.

3. Put the straw through the lid. You only want a little bit of the straw pushed in so that most of the straw is sticking above the top.
4. Use your play dough to seal around the straw. Only put the play dough on the outside of the pickle jar lid. Make sure the play dough covers around the hole. This is an important step.
5. Have a student place a marshmallow in the middle of the pickle jar and then screw the lid back on the jar. Make sure it is on tight.
6. Before you conduct the rest of the experiment have the students write down a hypothesis in their notebooks. A hypothesis is an educated guess and should include the reasons why something will happen.
7. Have a student begin to suck the air out of the jar. Watch what happens to the marshmallow. After the student has taken all of the possible air out of the jar, allow them to let go of the straw so that the air sucks back in to the jar. Pay attention to what is happening to the marshmallow.

Review:

Discuss what happened to the marshmallow when there was no air and what happened to it when their was air. Have the students write the conclusion in their notebooks and compare to the hypothesis they made. Ask the students to share if they saw anything that surprised them.