matter

917

Pot of water
Heavy water played an important role in the development of the atomic bomb. What is heavy water?

945

plastic bag on scale
I weighed this plastic, storage bag while it was empty. Then I opened it to fill it with air. Sealing the bag again, I put it back on the scale. Was its weight the same, more, or less? Why?

960

wood and ashes
The wood in this pile will be reduced to this much ash when it is burned. What happens to the rest of the mass from the wood?

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