Question

gas → liquid
solid → liquid
are changes in state of matter physical or chemical changes?
decide if the following are physical (p) or chemical (c) changes:
frozen chicken thaws on a kitchen counter
chlorine tablets dissolve in a swimming pool
plants convert water and carbon dioxide into sugar
an axe is used to chop a piece of wood into pieces
aluminum cans are melted during recycling
a carton of milk spoils after being left out on the counter
the metal fender of a truck rusts
gasoline combusts in the engine of a car
water condenses on a cold bottle of soda
vegetable oil is heated up to a boiling temperature
erosion causes rocks to fall down a cliff
molecules of water are broken apart into hydrogen and oxygen
ethanol lamp (with an image of an ethanol lamp)

Explanation:

To solve this, we determine if a change is physical (no new substance, just state/shape) or chemical (new substance formed).

1. Frozen chicken thaws: State change (solid to liquid), no new substance. P
2. Chlorine tablets dissolve: Dissolution (physical mixing), no new substance. P
3. Plants make sugar: Photosynthesis (new substance: sugar). C
4. Axe chops wood: Shape change, no new substance. P
5. Aluminum cans melted: State change (solid to liquid), no new substance. P
6. Milk spoils: Bacteria grow, new substances (spoiled products). C
7. Metal fender rusts: Rust (new substance, Fe₂O₃) forms. C
8. Gasoline combusts: Combustion (new substances: CO₂, H₂O). C
9. Water condenses: State change (gas to liquid), no new substance. P
10. Vegetable oil heated: State change (liquid, maybe less viscous), no new substance. P
11. Erosion breaks rocks: Shape/position change, no new substance. P
12. Water molecules break: Chemical decomposition (H₂O → H₂ + O₂, new substances). C

Answer:

s:

1. P
2. P
3. C
4. P
5. P
6. C
7. C
8. C
9. P
10. P
11. P
12. C