Question

which of the following always means a chemical reaction has occurred when you mix a powder into a liquid?

The powder dissolves in the liquid.

The liquid or the powder breaks down.

The liquid is and its boiling point.

You observe bubbles in the mixture.

Answers

GPT-4o mini
Among the provided options, the presence of **bubbles in the mixture** is the only indicator that a chemical reaction has occurred, though it might not always be the case. Bubbles can indicate the production of gas, which typically suggests a chemical change.

Here's a brief evaluation of the other options:

1. **The powder dissolves in the liquid**: This process is usually a physical change, not necessarily a chemical reaction. When a substance dissolves, it typically retains its chemical identity.

2. **The liquid or the powder breaks down**: This could indicate a chemical change, but breaking down can also refer to physical processes (like melting or dissolving) depending on the context.

3. **The liquid is at its boiling point**: This again can be a physical change (a change of state from liquid to gas) and does not necessarily indicate that a chemical reaction has occurred.

Therefore, **observing bubbles in the mixture** is the best indicator from the options provided that a chemical reaction has occurred.