Which units can be used to describe the thermal

energy within a substance?

The element that has the greatest electronegativity is

How do you determine the percent yield of a chemical reaction

Awhite powder is added to a solution. the images show observations made before the powder is added, just after the powder has been added, and a little while later. (the liquid in the small beaker is phenol red solution.) what evidence shows that a chemical change has taken place?