Question

part 2: signs of a chemical reaction
check (√) the box if the observation shows a chemical reaction occurred:
color change
temperature change (hot or cold)
gas produced (bubbles, fizzing)
solid forms in liquid (precipitate)
ice melting
sugar dissolving in water
part 3: physical vs. chemical changes
write p for physical change or c for chemical change:

1. ______ cutting paper
2. ______ wood burning
3. ______ water boiling
4. ______ iron rusting
5. ______ breaking glass
6. ______ baking a cake
7. ______ ice melting
8. ______ milk souring
9. ______ dissolving salt in water

10.______ fireworks exploding
part 4: identifying reactants and products
underline the reactants once and circle the products in each equation:

1. carbon + oxygen → carbon dioxide
2. sodium + chlorine → sodium chloride
3. methane + oxygen → carbon dioxide + water
4. zinc + hydrochloric acid → zinc chloride + hydrogen

Explanation:

• Part 2:
• Color change: A new substance with a different color may form in a chemical reaction.
• Temperature change (hot or cold): Energy is absorbed or released in a chemical reaction.
• Gas produced (bubbles, fizzing): A new gaseous substance is formed.
• Solid forms in liquid (precipitate): A new solid substance is formed.
• Ice melting: It is a physical change (change of state).
• Sugar dissolving in water: It is a physical change (dissolution).
• Part 3:
• Cutting paper: Physical change (no new substance).
• Wood burning: Chemical change (new substances like ash, carbon dioxide).
• Water boiling: Physical change (change of state).
• Iron rusting: Chemical change (new substance - rust).
• Breaking glass: Physical change (no new substance).
• Baking a cake: Chemical change (new substances due to reactions).
• Ice melting: Physical change (change of state).
• Milk souring: Chemical change (new substances due to spoilage).
• Dissolving salt in water: Physical change (dissolution).
• Fireworks exploding: Chemical change (new substances and energy release).
• Part 4:
• Reactants are on the left side of the arrow ($\to$), products on the right.

Answer:

• Part 2:
• Color change: Yes
• Temperature change (hot or cold): Yes
• Gas produced (bubbles, fizzing): Yes
• Solid forms in liquid (precipitate): Yes
• Ice melting: No
• Sugar dissolving in water: No
• Part 3:

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

• Part 4:

1. Underline: Carbon, Oxygen; Circle: Carbon dioxide
2. Underline: Sodium, Chlorine; Circle: Sodium chloride
3. Underline: Methane, Oxygen; Circle: Carbon dioxide, Water
4. Underline: Zinc, Hydrochloric acid; Circle: Zinc chloride, Hydrogen