Acetone would be a liquid at 42 degrees Celsius.

Here's why:

* Acetone's boiling point is 56 degrees Celsius. This means it transitions from a liquid to a gas at that temperature.

* Acetone's melting point is -95 degrees Celsius. This means it transitions from a solid to a liquid at that temperature.

Since 42 degrees Celsius falls between acetone's melting and boiling points, it will be in its liquid state.