Question

Which of the following is a sign a chemical reaction has occurred? A liquid changes to a solid when cooled. A liquid forms bubbles when heated. Two clear liquids combine and mix together. Two clear liquids combine and turn cloudy.

Answer 1

The last one “two clear liquid combine and turn cloudy” shows visual evidence that the two have combined and changed.

Answer 2

The best answer is, “Two clear liquids combine and turn cloudy.”

When water freezes form a liquid to a solid. That’s a physical change.

When water boils, it forms bubbles. That’s a physical change.

When you mix ethanol and water, they form a clear solution. That’s a physical change.