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.

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.

a  solution  is always transparent, light passes through with no scattering from solute particles which are molecule in size. the  solution  is homogeneous and does not settle out. a colloid is intermediate between asolution  and a  suspension. while asuspension  will separate out a colloid will not.

c. 75.7

i think that is the right