I dissolved two different white solids into water. One solid dissolved and gave off heat and the other became cold. Reading various texts online, I was not sure if these were physical or chemical changes. Some texts say if these solids are salts then these are physical changes. Other texts say since ionic bonds are broken, these are chemical changes. Which one is correct?
chemical change. Because even if they don't dissolve they well be the same
The correct answer is that both physical and chemical changes are happening in this scenario.
When a solid dissolves in water, it generally involves both physical and chemical processes. The physical process is the dissolution of the solid, which is a physical change. In this process, the solid particles are dispersed into the water, breaking apart the physical bonds between the particles. This results in the formation of a homogeneous solution.
The chemical process that may occur during the dissolution depends on the nature of the solid being dissolved. If the solid is an ionic compound, such as a salt, then chemical changes occur as well. Ionic compounds are composed of positive and negative ions that are held together by ionic bonds. When the solid dissolves in water, the water molecules surround the individual ions, breaking the ionic bonds and allowing the ions to move freely. This process is called ionization or dissociation.
Now, in relation to the heat changes you observed, they can provide some insight into the nature of the changes taking place. When a solid dissolves and gives off heat, it is an exothermic process. This indicates that energy is being released as the ionic bonds are broken. On the other hand, if a solid becomes cold when it dissolves, it is an endothermic process, which means it absorbs heat from its surroundings.
In conclusion, the dissolution of a solid in water involves both physical and chemical changes. The physical change is the dissolution itself, while the chemical change occurs when ionic compounds dissociate into their constituent ions. The heat changes observed during the dissolution can provide further clues about the nature of the changes taking place.