Everyone enjoys experimenting with things that either float or sink. In this science
experiment we will make some observations and try to figure out why lemons float and
limes sink. The answer is not so clear.

Materials
- 5 Large Lemons (try to pick lemons and limes of the same size)
- 5 Large Limes
- Fish Tank or Big Bucket, or Big Deep Bowl

Watch Video:  Floating Lemon Sinking Limes Experiment

Process Floating Lemons Sinking Limes Experiment

1. Add water to your fish tank, bucket or bowl. Use the scientific method to predict what will
happen when you drop in lemons and limes.

2. Make a prediction and drop in the lemons. Where you correct? Did they sink or float. They
should have floated.

3. Next make a prediction and drop in the limes. Where you correct? Did they sink or float?
The limes should sink. However, some may float or hover mid way.

4. Lets start to explore why they sink and float. Well the obvious first guess is the rinds of the
lemon and limes. Peel one of each. You will notice the lemon rind is thick and porous and
contains little tiny air pockets. Next the lime. The lime rind is not nearly as thick as the lemon
rind. It is thin a does not contain as much air.

5. Ok let's test out the rind hypothesis. Drop your peeled lemon and lime into the water.
What happened? Humm - they lemon still floats and the lime still sinks. That must mean it's
not the air pockets in the rinds making them float or sink!

6. Keep experimenting and try develop some more hypothesis to test.

The Science Behind Floating Lemons Sinking Limes Experiment:
Most people think at first the reason is the rind. After all many have done this same test with
oranges and found the following. An orange will float due to the air pockets in the rind. But
once you peel it and remove the air pockets in the rind, that orange will sink. So most
assume the same hold true of the floating lemon. But our test showed that not to be true.
What else could it be if not the rind?

The answer has to do with density. The USDA website indicates limes are 88.26% water
and lemons are 87.4% water. This may infer that lemons have a higher air content inside
than limes.

Digging a bit deeper we broke out the scale and tried to find a lemon and lime of similar
weight. We found a pair that weighed 99 grams. Once we knew the weight did the
calculation to find the volume for the lemon and limes. Using the water displacement
method, we found the lemon had a volume of 98 mL and the lime 89mL. (note: the water
displacement method to measure volume is done by filling a container with water to the top,
then adding the item you want to measure (lime or lemon in this case), letting the water spill
over the side of the container, and catching it in something else to see the volume).

Next we calculated
Density for the lemon and limes. The formula for density is Density =
Mass / Volume.

The Density for the lemon was: 99 grams (mass)  / 98 mL (volume) = 1.01

The Density for the lime was: 99 grams (mass)  / 89 mL (volume) = 1.11

Density of Water: 1.00 grams per mL.

Our math illustrates the density of the lemon was less that of the lime. With water
accounting for density of 1 gram per mL it becomes clear as to why the lemon floats and the
lime sinks. Bottom line, the lime is more dense than water so it sinks, the lemon is less
dense or about the same as water so it floats. The densities of the lemons and limes are
very close to the density of the water. Because of this any small differences like weight of a
specific lime could make it sink or float.

Now go and do the floating lemons and sinking limes experiment with your friends!