Question

1. what is the difference between endothermic and exothermic reactions?
2. on table 1, highlight all the endothermic reactions.
3. how could you use evidence to decide if a change is physical or chemical?

Explanation:

1. Endothermic reactions absorb heat from the surroundings, causing a temperature drop, while exothermic reactions release heat to the surroundings, causing a temperature rise.
2. Table 1 is not provided, so specific reactions cannot be highlighted. Endothermic reactions are those that take in heat (e.g., melting ice, photosynthesis, baking soda and vinegar reaction).
3. A physical change only alters the form/appearance of a substance without creating a new substance; evidence includes reversible changes, no new odor/color (temporary change), no gas/precipitate formation. A chemical change forms a new substance; evidence includes irreversible changes, new odor/color, gas production, precipitate formation, temperature change from a reaction.

Answer:

1. Endothermic reactions absorb heat from the environment, while exothermic reactions release heat into the environment.
2. Cannot complete: Table 1 is not included in the provided content. Endothermic reactions are heat-absorbing processes.
3. To decide:

• For physical change: Look for reversible changes, no new substance formed (e.g., melting ice, dissolving salt in water, where the original substance can be recovered easily).
• For chemical change: Look for irreversible changes, formation of a new substance (evidenced by new odor, color change, gas bubbles, precipitate formation, or a sustained temperature change from a reaction).