1 #
Heat
2 #
a An exothermic reaction gives out thermal energy to the surroundings.
b An endothermic reaction takes in thermal energy from the surroundings.
3 #
In reaction B, the water in the beaker gets warmer because the reaction between sodium chloride and silver nitrate is exothermic. The reaction gives out thermal energy to the surroundings, so the water temperature rises.
4 #
In D, the water under the beaker freezes because the reaction between barium hydroxide and ammonium chloride is endothermic. The reaction takes in thermal energy from the surroundings, including the water under the beaker. This makes the water so cold that it freezes.
6 #
All chemicals contain chemical energy. It is stored in their bonds.
7 #
In B some chemical energy is being changed into thermal energy. This statement is correct because during the reaction between sodium chloride and silver nitrate, chemical energy stored in the bonds changes into thermal energy, which heats up the water in the beaker.
