Workbook Pages

Key Ideas

• Materials are made of molecules, and molecules are built from atoms, which behave like building blocks.
• In a chemical reaction the atoms themselves do not change. Only their arrangement changes.
• Burning is the oxidation of carbon: wax plus oxygen becomes carbon dioxide, and the energy released was stored in the wax all along.
• You can spot a chemical reaction two ways: something new appears, or energy is given off or required. A mixture does neither.
• Your body runs the same reaction as the candle, in many small steps, which is why you cannot live without oxygen.

• Molecule: The basic particle of a material. Nearly every material is made of molecules of one sort or another.
• Atom: The smaller building blocks molecules are made from.
• Chemical reaction: A rearrangement of atoms that makes different substances, giving off or taking in energy.
• Oxidation: A reaction in which oxygen atoms join with something else. Burning is the oxidation of carbon.Potential energy: Energy stored in an arrangement, waiting to be released.
• Respiration: The slow, controlled oxidation of food inside a living body, releasing energy in a form cells can use.

1. If you burned a candle inside a perfectly sealed box and could weigh the whole box before and after, what would you expect the weight to do? Defend your answer.
2. Baking a cake requires heat and produces something you cannot turn back into batter. Mixture or chemical reaction? Say which clue settles it.
3. Every fire and every breathing animal on Earth takes oxygen out of the air and puts carbon dioxide in. So why has the air not run out of oxygen by now?

• Sugar, salt, sand, water, vinegar, baking soda, cooking oil, a wet iron nail, clear jars, and an adult