Evidence Chem and Phys & Types Combustion & Tests for Gasses

What are some common pieces of evidence that suggest a chemical change has occurred?

1. Production of a gas (e.g., bubbles)

2. Formation of a precipitate (a solid formed from two liquids)

3. Change in color

4. Change in temperature (either heat released or absorbed)

5. Emission of light or sound

6. Change in odor

7. Formation of new products with different properties

8. Not reversible

What are some common pieces of evidence that suggest a physical change has occurred?

1. Change in state

2. Change in size or shape

3. Dissolving a substance (e.g. creating a solution)

4. Mixing substances without forming a new one (mixture)

5. Change in texture

6. No new products are formed; substances retain their original properties

7. Reversible

Combustion: Oxygen with a hydrocarbon (or other compounds containing C, H, and sometimes O)

Carbon dioxide and water

Combustion: Oxygen with a metal element

Metal Oxide

Tests for CO2

1. lit splint goes out

2. bubble it though limewater and look for a precipitate

Tests for O2

lit splint glows brightly

Test for H2

lit splint makes it pop