Dissolving Sugar in Water: Chemical or Physical Change?

Dissolving Sugar in Water: Chemical or Physical Change?

Is dissolving sugar in water an example of a chemical or physical change? This process is a little trickier to understand than most, but if you look at the definition of chemical and physical changes, you'll see how it works. Here are the answer and an explanation of the process.

Relating Dissolution to Change

Dissolving sugar in water is an example of a physical change. Here's why: A chemical change produces new chemical products. In order for sugar in water to be a chemical change, something new would need to result. A chemical reaction would have to occur. However, mixing sugar and water simply produces… sugar in water! The substances may change form, but not identity. That's a physical change.

One way to identify some physical changes (not all) is to ask whether the starting materials or reactants have the same chemical identity as the ending materials or products. If you evaporate the water from a sugar-water solution, you're left with sugar.

Whether Dissolving Is a Chemical or Physical Change

Any time you dissolve a covalent compound like sugar, you're looking at a physical change. The molecules get further apart in the solvent, but they don't change.

However, there's a dispute about whether dissolving an ionic compound (like salt) is a chemical or physical change because a chemical reaction does occur, where the salt breaks into its component ions (sodium and chloride) in water. The ions display different properties from the original compound. That indicates a chemical change. On the other hand, if you evaporate the water, you're left with salt. That seems consistent with a physical change. There are valid arguments for both answers, so if you're ever asked about it on a test, be prepared to explain yourself.