Lesson: Density
Materials
-raw eggs
-plastic cups
-salt
-water
-plastic straws
-cooking oil
-food coloring
-empty water bottles
-Honey
-liquid dish soap
-veggie oil
rubbing alcohol
Opening Discussion
-What is density? (mass per unit volume, how many atoms per how much space)
-How does density work? (substances that are more dense will sink to the bottom of
a mixture and substances that are less dense with settle towards the top)
-Examples of density in everyday life (boat on water, salad dressing, ice)
-elaborate on ice example
Activity #1 “Eggs Float”
*Have kids make hypotheses about what will happen*
1. Fill a glass about halfway full with water.
2. Place an egg into the water.
3. The egg will sink because it is denser than the water.
4. Start adding salt to the water one tablespoon at a time.
5. Stir the water to help dissolve the salt.
6. Ask them what happened and why they think it happened.
7. Also ask how much salt they had to add to get their egg to float.
Follow-up discussion:
-Adding salt to the water squishes more molecules into the water. This makes the
water more dense.
- When there was no salt in the water, the egg was denser than the water, therefore
it sank.
-Adding salt to the water makes the water denser than the egg, which makes the egg
float.
-If you weigh a cup of saltwater and a cup of fresh water, the saltwater will weigh
more than the fresh water even though it is taking up the same amount of space (a
cup).
-This is because the saltwater is more dense than the fresh water.
Activity #2 “Rainbow Density Tower Demonstration”
Demonstrate the effects of Density by layering the following liquids in the following
order:
1.Honey
2. Corn Syrup
3. Dish Soap
4. Water
5. Veggie Oil
6. Rubbing alcohol
This will create a tower stratified based on densities.
Follow-up Questions
-Why aren’t the liquids mixing?
-Which liquid is most dense? Least dense?
Activity #3 “Lava Lamps”
1.Fill the plastic bottles with water
2.Allow the kids to add oil
3. Seal the bottles really tight!
4. Try shaking the bottles and see what happens
Follow-up Disscussion
-What did you observe?
-Why did layers appear?
-What is more dense, water or oil?
-Polarity of water and strong intermolecular forces prevent mixing