16) Na (s) + H2O(L) ---> H2 (g) + NaOH (aq)
17) O2 (g) + NH3 (g) --->H2O (L) + HNO3 (aq)
18) K (s) + Cl2 (g) ---> KCl (s)
19) Al (s) + HCl (aq) ---> H2 (g) + AlCl (aq)
20) Na3PO4 (aq) + CaCl2 (aq) ---> NaCl (s) + Ca3(PO4)2 (s)
The change is thermal energy to chemical energy. Sugar contains a lot of chemical potential energy which is why living things use it as a source of energy. The process of photo synthesis takes light from the sun to convert carbon dioxide and water into sugar and oxygen. That process is basically turning the thermal energy from the light into chemical energy in the sugar.
I hope this helps. Let me know if anything is unclear.
