Here's why:
Physical Change:
* No new substances are formed: When a substance dissolves in water, the molecules of the substance are simply dispersed throughout the water molecules. The substance itself remains chemically unchanged. For example, when salt dissolves in water, the salt molecules are surrounded by water molecules, but the salt itself doesn't change its chemical composition.
* The change is reversible: The dissolved substance can be recovered by evaporating the water.
Chemical Change:
* New substances are formed: In some cases, dissolving in water can lead to a chemical reaction where the substance reacts with water and forms a new compound. For example, when sodium metal dissolves in water, it reacts with water to form sodium hydroxide and hydrogen gas.
* The change is not always reversible: The new compound formed might not be easily separated from the water.
In summary:
* Dissolving in water is a physical change for substances that do not react with water.
* Dissolving in water is a chemical change for substances that react with water.
To determine whether dissolving in water is a physical or chemical change for a particular substance, you need to consider whether a chemical reaction occurs.
