Signs of a chemical reaction
Mix kitchen substances and look for evidence that a new substance has formed: gas bubbles or a new solid.
Core concept
Gas, a new solid or a colour change can show a chemical reaction
Topic: Chemical reactions
In a chemical reaction, substances change into new substances. We cannot see the particle: A tiny piece that matter is made of, far too small to see. All key words rearranging, but we can look for evidence: What you saw or measured that shows whether an idea is right. All key words: bubbles of a gas, a new solid appearing in a liquid, a colour change, or a change in temperature: How hot or cold something is, measured in degrees Celsius (°C). All key words. When a substance only dissolve: To mix into a liquid so completely that you can no longer see the pieces. All key words or changes shape, no new substance forms. That is a physical change.
What you will learn
- List observable evidence that a chemical reaction has happened.
- Identify gas production and the formation of a new solid as evidence of a reaction.
- Tell a chemical change apart from dissolving, which is a physical change.
Before you start
- Know that dissolving does not make a new substance. Try the Dissolving experiment first.
Materials
- Vinegar
- Baking soda
- Milk
- Water
- Table salt
Equipment
- 3 beakers (100 mL)
- Stirring rod
Procedure
- Pour 20 mL of vinegar into Beaker A, then add 5 g of baking soda.
- Pour 20 mL of milk into Beaker B, add 20 mL of vinegar and stir.
- Pour 20 mL of water into Beaker C, add 5 g of salt and stir.
- Record the evidence you see in each beaker, or the lack of it.
How this simulation is simplified
- The bubbling is shown continuing. In real life it slows down and stops once the baking soda or the acid in the vinegar is used up.
- Changes in temperature are not shown here, although they can also be evidence of a reaction.