Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: A student conducts an experiment with potato slices and salt water. The student wants to determine if a higher concentration of salt will affect the amount of water a potato slice absorbs. Which tool would be best to compare the masses of the potato slices?
Balance.