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Float or Sink: Lemons and Limes

Lemons and Limes, they're the same. Well, except for the color, taste... and density.

The students will test the buoyancy of lemons and limes and determine the density of each fruit by placing each fruit into water.  

A Few Lemons and Limes (try to find some that are similar in size)

1) Ping Pong Ball

2) Marble

3) Clear Container of Water

4) Scale

Vocabulary:
Buoyancy- The power to rise or float in liquid if the object is less dense than the fluid
Density- mass per unit of volume

Drop a ping pong ball into the water, the ping pong ball will float. Explain that it is because the ping pong ball is light weight, and its density is less than that of the water. Therefore the ping pong ball is very buoyant.

Demonstrate the same thing with a heavier object, such as a marble. The marble will sink to the bottom of the container of water. The density proves to be more than that of the water, so a marble is not buoyant.

Now, try this experiment with the lemons and limes.

Drop a couple lemons into the container of water. They will float.

Drop the limes into the container of water. They won’t float. If they don’t sink it is observable that they will barely float. Why?

Student may assume it has to do with the rind. Remove the rind from each a lemon and a lime. Drop each into the water. Again, the lemon will float, and the lime will sink.

Weigh your Lemons and your Limes. Record the Data in grams.

Calculate the density of the lemons and the limes. D=m/v; Density equals mass over volume. To find the volume of the lemons and limes, you can use the water displacement method. Fill a container to the top, and place the fruit in. Measure the water (mL) that has spilled out and that is the volume for the fruit.

Have students compare and contrast lemons and limes.  How are they different?  How are they similar?  Poise the question if lemons and limes will either float or sink in water.  Have students make their predictions. 

Although, the two fruits are very similar they have different densities. Were the results of the experiment what they originally predicted? Review with students which fruit was more buoyant. Which fruit had a higher density?

Discuss with students the nutritious benefits of citrus fruits.