Chemistry controlled assessment
Temperature changes when salt dissolves
I am investigating factors that affect the temperature change when a salt dissolves in water. Understanding energy changes when salt dissolves in water is important because its used in several different industries for example sports packs are used for the damage caused by sprains, twists or bruises the sports packs can reduce this by wrapping something cold around the injury.
When an ionic salt dissolves in water the attraction between molecules of water and ions cause energy to be released. Separating the oppositely charged ions requires energy, so energy is absorbed. In an endothermic reaction the energy absorbed is said to be greater than the energy released this creates an endothermic reaction making the temperature decrease.
Factors that affect the temperature change when salts dissolve
Type of ionic salt – Ionic salts all have different properties, some with strong electrostatic attraction, others with weaker. This is important as if they have a stronger attraction there will be a larger temperature change. As more energy needs to be absorbed .
Mass of salt – If there is more salt, there will be more ions which will need more energy is needed to break the bond between the ions. This will create a greater decrease in temperature.
Container – The container is a variable which determines if external heat affects the temperature change in the sports pack.
Volume of water – If the volume of water is greater there will be a smaller change in temperature, as the same amount of energy will be absorbed from a greater volume of water