If any of you attempted to make syrup following the recipe we posted, I’m sure you noticed something as your concoction boiled. The water evaporated, leaving the sticky, sweet and thick syrup. This syrup that remained was much, much thicker than the liquid that you started with. The thickness of syrup can be measured by density. Density is a measure of how tightly packed the molecules are in a substance.
Feathers and Bricks
Have you ever been asked this trick question: “Which weighs more – a pound of feathers, or a pound of bricks?” The answer, if you think for a moment, is that they both weigh the same! One pound of anything weighs . . . well . . . a pound! So, the fact that you are comparing feathers and bricks does not make a pound of either of those things weigh more or less than the other.
We could pose the question a little differently in regards to density though. Which is more dense, a pound of feathers, or a pound of bricks? The answer would almost certainly be that the pound of bricks is denser. One brick probably weighs a pound. (Picture a brick the size of your shoe). How many feathers would equal a pound? (I’m picturing something like a pillowcase stuffed with feathers). Of those two pictures, which is denser? The bricks, of course! If you took a fistful of feathers the same size as a brick, they would have far less matter than the brick does.
Liquid densities are really interesting to explore. A liquid that is less dense than another liquid will float on top of it! If you pour a glass of water on syrup, the water will float on top of the syrup.
To test your knowledge of liquid densities, try out this experiment below. You’ll feel like a scientist and a magician as you stack liquids on top of one another.
Layers of Liquids - Exploring Density
- A tall glass cylinder to hold your liquids. Ideally, it will be like a graduated cylinder that chemists use, but if you have a tall, narrow glass vase that should work as well.
- Cups for each liquid ( 9 oz. each)
Optional Household Objects –
1. What you will be doing is gradually adding each liquid on top of the others, starting with the densest at the bottom. Pour 8 oz. of each liquid into a separate cup (if you have clear cups, they work best for observation).You should have 8 cups. If you would like to add color to any of the clear liquids, now is the time to use of your food coloring. Try using all different colors, so you can clearly see the differences in your column.
2. Prior to reading the order of densities, sit down and look at all your liquids and write down the density order that you think will describe the column. If you are doing this with young children, have them draw a picture of what they think the column will look like.
3. Now that you have made what we scientists call a hypothesis, you can read the correct order. Slowly, begin by pouring the honey into your cylinder. You should pour in such a way that the liquid travels down the middle of the cylinder WITHOUT touching any of the sides of the cylinder. Continue pouring each liquid in this manner. You will be pouring the light corn syrup next.
PURE MAPLE SYRUP
LIGHT CORN SYRUP
BOTTOM OF CONTAINER
5. Have your children draw a new picture of the density column with the correct order of liquids. The first was their original hypothesis. Now, they can compare their hypothesis with what the outcome actually looked like.
6. Continue experimenting with your density column by dropping small household objects into it. Your goal here is to determine the approximate density of each object in relation to your liquids. Before dropping each object into the column, guess where it will settle. For example, if you choose to drop in a bobby pin, you might guess that it will rest on the layer between the maple syrup and the milk. If this is your hypothesis, then you are saying that you think the bobby pin is more dense than milk but less dense than the maple syrup. Using the second drawing, you can continue adding elements to your density column drawing!
- You are using the exact same volume of each liquid, but these liquids have different masses. Liquids with greater mass (higher density) have more molecules packed into the same amount of space than those with smaller amounts of mass (lower density)!
Inspiration for this Experiment was from: