Science in the Kitchen: Density

Materials:

1. Milk
2. Pancake syrup
3. Water
4. Vegetable oil
5. Dawn dish soap (blue)
6. Graduated cylinder (or tall narrow clear container)
7. Small cups
8. Plastic droppers

Activity:

Have you guys noticed that whenever something with oil is cooking, the oil floats on top of the water? Do you know why that is? Well, this is because the density of oil is less than the density of water. Has someone ever heard that word: density? Density is how much stuff is packed into a particular area. That means the volume, or the quantity, of two different things might be the same but their densities are different. For example, I measured the weight of these feathers and the weight of this flour, and it is the same. But which one occupies less space? Yes, the feathers occupy more space because they are less dense. But we use other liquids in the kitchen besides water and oil. Can you mention some? What about milk, honey and dish washer liquid? Which one has the highest density? Let’s answer that question with an experiment!

You have in front of you the same quantity of liquids that we can find in the kitchen. Milk, pancake syrup, water, vegetable oil and dish soap. You also have a cylinder. We are going to pour the liquids very slowly and see if they have different densities. Which liquid do you think will have the greatest density? Okay, write that in your notebook. Now take any liquid, put it in your dropper, and put it in the cylinder slowly. Now do the same for all the liquids. What happened? Which one has the greatest density? Correct! The pancake syrup is at the bottom because it has more mass in the same volume as the other liquids. Where is the oil? Is it denser than water? No, it’s not, this is why it floats while we are cooking.

It looks cool in that cylinder, but what if we calculate the densities? Let’s calculate the density of oil and water! The equation we use to calculate density is the mass, which is related to how much something weights, divided by the volume. The equation is in your notebooks and I have given you the mass and volume of oil and water. Let’s all calculate it together! As a review can someone tell me what density is?

Student notebook:

Which liquid do you think is denser? ______________________________________

Write the order of the liquids:

Top —-> Bottom:  ____________________________________________________________________________

Density = Mass / Volume

Water: Mass = 5g    &     Volume = 5ml

Density of Water = _______________ g/ml

Oil: Mass = 4.6g     &     Volume = 5ml

Density of oil = _______________ g/ml