MASS AND VOLUME

Purpose

To understand conservation of mass and non-conservation of volume.

Opening Questions

1) Why are both mass and volume often measured in chemistry investigations?

2) What advantages or disadvantages might there be for measuring one over the other?

Materials

Water, ethanol, pipets, beakers, balance

Instructions

Accurately measure the volume of exactly 25.00 mL of water (measured by pipet). Weigh an empty 100 mL beaker then put the water in the beaker and weigh it again.

Mass of empty beaker:________________

Mass of beaker and water: __________________

Mass of Water: ________________ (mass of beaker and water – mass of beaker)

Do the same for 25.00 mL of ethanol. Put it in a different 100 mL beaker and find its mass.

Mass of empty beaker: ______________________

Mass of beaker and alcohol: ____________________

Mass of alcohol: _________________ (mass of beaker and alcohol – mass of beaker)

Combine the two liquids and accurately measure both the volume (using a 50 mL graduated cylinder) and mass of the combined solution.

Volume of combined solution: __________________

Mass of empty beaker:________________

Mass of combined solution and beaker: __________________

Mass of combines Solution: ______________ (mass of combined solution and beaker – mass of beaker)

Questions

1) Is the sum of the mass of water plus the mass of ethanol equal to the total mass of the solution? Record your measurements to support your conclusions.

2) Is the sum of the volume of water plus the volume of ethanol equal to the total volume of the solution? Record your measurements to support your conclusions.

3) Review the advantages of measuring mass and volume based on the results of this investigation.