How to use density bottles:
Demo & Discussion – For this part of the lesson, students will not handle the bottles, they will answer discussion questions based on their observations only.
- Share observations about the bottles.
- What do the bottles have in common?
- What is different about the bottles?
- What do you think the original contents of the bottle were?
- What phases of matter are shown?
- Are any of these bottles empty? Explain.
- Do all of these bottles have air in them?
- Which bottle has more air in it: Cotton Balls or Water? Explain.
- Which bottle is filled the most? Least?
- Which bottle has has the most ‘stuff’ in it? Least?
- Which bottle is the heaviest? Lightest?
- How would you order these bottles from lightest to heaviest?
- Estimate the mass of each bottle in grams.
- Which bottle is the densest?
- How would you arrange these bottles from least to most dense?
- Which of these bottles can have more of the same ‘stuff’ added to the inside of the bottle? Explain.
- Which bottle(s) would float in a tank of water? (I do this at the very end of the lesson with everyone at the sink)
Hands On Exploration
- Each group will have one set of bottles or take turns using the demo bottles and sharing their findings.
- Using a triple beam balance, the volume of the bottles, and a tank of water, answer as many of the questions above as you can. (for our calculations, we use the volume of the bottle’s original content (500 mL of sport drink) to give us an approximate density, not the actual density – for comparison purposes only)
- How did your findings compare to your observations and predictions?
- Dunk tank – time to find out which one will float!
Further Exploration
Give each group of students a new set of bottles (ones that they have brought in from home) and have them make observations, predictions, and density calculations.
Additional Bottle Ideas:
- Rocks/pebbles
- laundry detergent – liquid or powder
- paper clips
- paper shreds
- crayons
- marbles
- flour
- bread crumbs
- coffee beans
- beans
- different shapes of pasta
- pom-poms
- pop corn kernels or popped
- Lego pieces
- salt
- dish-soap
- beads
- yarn/string
- etc…
Have each student bring in a bottle from home filled with the contents of their choice so that you have enough bottle to compare. Match similar bottle shapes/sizes together for each group or match similar contents in different sized bottles for comparison.
You can also use these bottles as part of a Triple Beam Balance Activity (blog entry).
Middle School Science Blog 
Love this. Do you have any kind of answer key or guidance of expectation for the above questions?
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Karen, During our discussion, I let the students share their thoughts and either disagree or agree with each other’s statements – I mostly facilitate and ask question to help them express their thoughts clearly. I don’t give any indication as to if their answer is correct or not.
Once the students have handled the bottles and determined the masses and relative densities, we talk about our findings and share our conclusions. The main idea of this exercise to get an idea of what density means in a way that is tangible to the students. For example, the bottle with the cotton balls, we can squeeze in many more cotton balls into the bottle, what happens if we do that?
Another comparison I like to give is I ask the students how much do you think this bottle would weigh if filled with solid gold. If the volume is 500 mL and the density is 19.3 g/mL or g/cm3, the mass of the gold would be 9,650 grams with a value of hundreds of thousands of dollars! For the dunk tank, we simply introduce that the density of the bottle is either more or less than the density of water. Hope that helps! ~Liz
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