1. On two large marshmallows (oxygen atom) color 8 purple dots to represent oxygens 8 protons. Then, color 8 pink dots to represent the 8 neutrons of the most common isotope of oxygen. (refer to picture of oxygen form the periodic table)
2. Color 4 mini marshmallows purple.
3. Color 2 mini marshmallow pink.
4. Start with ordinary water. “ordinary” hydrogen consists of one proton and no neutrons. (refer to picture of hydrogen form periodic table)
5. Take 2 toothpicks and attach a single proton to each one. Then attach each toothpick to one oxygen marshmallow. This represents “ordinary” water.
6. Next make heavy water. Deuterium is an isotope of hydrogen that has one neutron. Make two Deuterium atoms by taking two toothpicks and attaching one proton and one neutron marshmallow to each toothpick. Then attach both toothpicks to an oxygen marshmallow. This represents heavy water.
7. Make some observations about the differences. Be prepared to be called to discuss your observations.
8. Proceed to the handout (see adjacent box)
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“Ordinary” Water |
Heavy Water |
Color-coded model drawing |
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# of H
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Mass of H
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# of O
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Mass of O
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Molecular mass
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Total number of neutrons |
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Total number of protons |
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1. What is the mass of a common hydrogen atom?
2. What is the mass of one molecule of heavy water?
3. What is the mass of a hydrogen in a heavy water molecule?
4.What is the mass of one molecule of “ordinary” water?
5. Why is it called “Heavy Water”?