Lesson 49: Mixtures vs Reactions
Mixtures combine substances, while chemical reactions form new ones. This lesson covers evidence for chemical change and the movement of atoms and energy during processes such as combustion and respiration.
Key Ideas
- Matter is made of tiny building blocks called atoms. Atoms can join together to make molecules.
- A chemical reaction rearranges atoms to make new substances. The atoms do not simply disappear.
- A burning candle uses wax and oxygen. The reaction gives off light and heat and makes carbon dioxide and water.
- Bubbles, a color change, or a temperature change can be clues to a reaction. A clue alone does not prove that a new substance formed.
- Living cells use chemical reactions to release energy from food. This process supports growth, movement, and other life activities.
Vocabulary
- Atom: A tiny building block of matter. Each kind of element has its own kind of atom.
- Molecule: A group of two or more atoms joined together.
- Mixture: Two or more substances mixed together, such as sand and salt.
- Chemical Reaction: A change in which substances become new substances.
- Oxidation: A kind of chemical change. Rusting iron and burning a candle are examples.
- Cellular Respiration: The process cells use to release energy from food.
Discussion Questions
- 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.
- Baking changes a batter through several physical and chemical processes. What evidence would show that new substances formed?
- Many fires and animals use oxygen. How do plants help put oxygen back into the air?
Supplies
- Sugar, salt, sand, water, vinegar, baking soda, cooking oil, a wet iron nail, clear jars, and an adult