6th Grade

These 6th grade science fair projects will introduce young scientists to the critical scientific concepts of mass, volume, and density. Consider doing both of these projects in order to learn the concepts and then apply them to a scientific study.

What does it mean when you say something is “big?” This may seem like a silly question, but in fact it’s more complicated than it seems at first.

Scientists describe the “size” of an object in two ways: mass and volume. Volume is how much space an object takes up; mass is how much molecular “stuff” it contains. Density is the ratio of mass to volume.

Project #1: Measuring Mass, Volume, and Density

These 6th grade science fair projects will teach you how to measure and calculate mass, volume, and density, which will be a crucial skill for Experiment 2.


  • 10 toys, fruits, silverware, or other small objects that you don’t mind getting wet
  • 4-cup measuring cup
  • Postal scale or small balance scale


1. Make a data chart with rows for each of your 10 objects and columns for mass, volume, and density

2. Fill the measuring cup up to the 2-cup mark

3. Weigh each object on the scale. Make sure your measurements are in grams for full scientific accuracy. If your scale does not measure in grams, use a conversion chart.

4. Drop each object in the water and make sure it is fully submerged. See how much the water level goes up.

5. Subtract 2 (the initial volume of water) from the new water level to get the volume of the object. Can you see why we measure volume in this way? If your measurement is in cups or liters, convert it to cubic centimeters using a conversion chart.

6. You should now have mass and volume measurements for each of your 10 objects. To calculate density, simply divide the mass by the volume. Write this number down on your data sheet with the unit “grams per cubic centimeter” or “g/c3”

*TIP: This makes especially impressive 6th grade science fair projects if you can come up with a hypothesis beforehand about which toys or objects will be the most dense. Think about what density means, and make an educated guess.


Project #1: How Much Liquid is in an Orange?

You know how juicy a tasty orange can be, but just how much juice is actually in one of those oranges? In thee 6th grade science fair projects, we will figure out roughly the ratio of juice to pulp in an orange by both mass and volume.


  • 5 oranges, any size
  • strainer
  • postal scale
  • 4-cup measuring cup
  • spare bowl
  • Hand towel
  • soup spoon or mechanical juicer (optional)


1. Come up with your hypothesis – what percentage of the orange is made of liquid, and how much is solid?

2. Weigh your measuring cup on the postal scale. Make sure all of your measurements are in grams.

3. Label the oranges 1-5 and prepare a data chart to write down information about each orange

4. Measure the oranges’ mass and volume, just as we learned in Experiment 1

5. Cut one orange in half and, using your spoon or mechanical juicer if you have one, squeeze it out into the bowl. Try to get ALL the liquid out, or as much as you can. Make sure that any liquid that comes out of the orange makes it into the bowl.

6. Pour the juice out of the bowl, through the strainer and into the measuring cup. Take whatever pulp was strained out and put it back into the empty orange skins.

7. Write down the volume of liquid in the measuring cup. This is the “liquid volume” of your orange

8. Place the measuring cup on the scale and subtract the weight of the cup itself to get the “liquid mass” of the orange.

9. Calculate the relation between liquid mass and full mass as a percentage. Do the same for the relation between liquid volume and full volume.

10. Repeat for all 5 oranges. Plot your results on a graph. These 6th grade science fair projects are even better if you calculate the average percentage for all volumes. Was your hypothesis confirmed?

*Study Question: which part of an orange is more dense, the liquid or the solid parts?


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