Question

how can you tell that a chemical change has occurred? when the change occurs, there are clues/signs: • a change in color • a new odor is produced • gas is produced • the temperature changes • a solid is formed (precipitate) • light is released write the evidence shown in the chemical changes below by writing one of the words in bold above. there may be more than one possible answer. the first one is done as an example. color 1. apple turns brown after reacting with oxygen in the air 2. mixing vinegar and baking soda causes bubbles 3. mixing milk and vinegar makes curds 4. avocadoes turn brown after reacting with oxygen in the air 5. wood burning 6. copper metal on a roof turns green after reacting with oxygen in the air 7. bread dough rises from gas bubbles produced when yeast reacts with sugar 8. when sodium and chlorine make table salt, it releases heat during the reaction 9. food spoils and smells bad 10. adding food coloring to water causes a color change. why is this not evidence of a chemical reaction?

Explanation:

Step 1: Analyze each question

For question 2: Mixing vinegar and baking soda causes bubbles. Bubbles are gas, so the evidence is Gas.
For question 3: Mixing milk and vinegar makes curds (a solid). So the evidence is Precipitate (solid formed).
For question 4: Avocadoes turn brown (color change). So the evidence is Color.
For question 5: Wood burning releases light and heat (temperature change, light). So possible evidence: Light (or Temperature).
For question 6: Copper turns green (color change). So evidence is Color.
For question 7: Bread dough rises from gas bubbles (gas produced). So evidence is Gas.
For question 8: Reaction releases heat (temperature change). So evidence is Temperature.
For question 9: Food spoils and smells bad (new odor). So evidence is Odor.
For question 10: Adding food coloring to water is a physical change (no new substance, just mixing). Chemical reactions form new substances; this is a physical mixture, so no chemical reaction.

Step 2: Summarize answers

1. Gas
2. Precipitate (Solid)
3. Color
4. Light (or Temperature)
5. Color
6. Gas
7. Temperature
8. Odor
9. It's a physical change (mixing, no new substance), so not a chemical reaction.

Answer:

1. Gas
2. Precipitate (Solid)
3. Color
4. Light (or Temperature)
5. Color
6. Gas
7. Temperature
8. Odor
9. It is a physical change (mixing, no new substance formed), so it is not evidence of a chemical reaction.