Question

1. an unexpected change in ___ is a sign that chemical reactions may have occurred. word bank: temperature, light, odor, evidence, molecules, color, precipitate, gas.

Explanation:

In a chemical reaction, an unexpected change in temperature can occur due to heat being released (exothermic) or absorbed (endothermic). Light can be emitted in some reactions (e.g., combustion). A change in odor can happen as new substances with different smells are formed. A color change is a common sign (e.g., rusting of iron changes color). Formation of a precipitate (insoluble solid) from solutions is a sign. Release of gas (bubbles) is also an indication. All these are evidence that a chemical reaction may have occurred.

Answer:

temperature, light, odor, color, precipitate, gas