What is evidence that a chemical change has happened? A. A substance changes into a new kind of substance. B. You observe a color change. O C. The amount of matter increases. D. The temperature of a substance increases or decreases.

11. phosphorus-32 is radioactive and has a half life of 14 days. how much of a 124 mg sample of phosphorus-32 is present after 56 days? a) 7.75 mg b) 15.5 mg c) 31.0 mg d) 62.0 mg

Analyze how limestone is weathered and identify the features that are formed as a result of this dissolution

Which statement about hf is true? it is zero for any compound in its standard state. it is positive when the bonds of the product store more energy than those of the reactants. it is negative when a compound forms from elements in their standard states. it is zero for any element that is in the liquid state.