Two changes are described below. A. Ice melts to form water. B. Sugar cubes dissolve in hot coffee. Which statement is true about thw two changes? A. Both are chemical changes because there is a chage in the composition of ice and sugar.
B. Both are physical changes because there is a change in the physical states of ice and sugar.
C. A is a physical change due to a change of state, but B is a chemical change becaue new molecules are formed.
D. A chemical chage due to a change of state, but B is a physical change because new molecules are formed.

Both are physical changes because there is a change in the physical states of ice and sugar

Explanation:

1. melting of ice to water is a change of state from solid to liquid, although there is a change in the physical state but the chemical nature of the water remain unchanged. no new substance is produced since ice and water is the same chemically. since the reaction can be reversed by freezing. This shows a physical change

2. Dissolving sugar cubes in hot coffee is also a physical change since the sugar is dissolved into the coffee but the chemical natures of the sugar and the coffee remain the same. no new substance is formed.  that is a chemical change

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.