Yes, acetone changes volume when combined with water. This is because acetone and water are not perfectly miscible, meaning they don't mix together to form a single uniform solution at all proportions.

Here's why:

* Non-ideal mixing: The interaction between acetone molecules and water molecules is not as strong as the interaction between molecules of each substance individually. This leads to a change in volume when they are mixed.

* Volume contraction: When acetone and water are mixed, the volume of the mixture is slightly less than the sum of the volumes of the individual components. This is because the acetone molecules are smaller than water molecules and can fit into the spaces between water molecules, leading to a tighter packing.

Important note: The change in volume is relatively small, but it is measurable.

In summary: While acetone and water do mix, the mixing is not ideal, resulting in a slight volume change (contraction).