According to the collision theory when can I chemical reaction occurs

If the mass of the products measured 120g what would the mass of the reactants a. 30g b. 60g c. 120g d. 240g

Compare and contrast physical changes with chemical changes.

Melting and boiling are endothermic processes. this means that these processes absorb energy from their surroundings in order to occur. use this information and the data you collected in the phase change gizmo to describe what happens to the temperature of water when you boil it, then explain why this result occurs.