by Liz LaRosa

www.middleschoolscience.com

Materials :

• Time Period : 1 1/2 - 2 - 45 minute classes
• Food coloring : red, yellow, blue (ratio = 5 drops / 100 mL water)
• large plastic lunch trays, one per group of 4 students or per 2 students

Each pair of students/group will have the following on their lunch trays :

• 6 test tubes
• test tube rack
• 1 or 2  pipettes
• 50 or 100 mL beaker (or larger) with Red liquid
• 50 or 100 mL beaker (or larger) with Blue liquid
• 50 or 100 mL beaker (or larger) with Yellow liquid
• 1 beaker of clean water
• 1 empty beaker
• 2 - 25 mL graduated cylinders
• 2 - 10 mL graduated cylinders
• 1 wax pencil
• goggles
• apron

Results: 

Answers: http://www.middleschoolscience.com/chemanswers.htm

TIP: make sure the students rinse out the graduated cylinders and test tubes to avoid contamination between measurements.

At the end of the lab, if all 6 test tubes look near level, you know that they were careful in their measurements!

This is a great lab! The kids love it! I use it right before we do chemical reactions as a practice so that when we do use REAL chemicals, they have a feel for the equipment and the safety procedures that need to be followed.

When done, students should have 63 mL of liquid.  Spillage, incorrect measurements and excess water from rinsing are factors to change the total.

You may be able to complete this lab in one class period, but it will most likely take a period and half, if not two full classes. Be sure to have plenty of test tubes and racks to save the results until the next day. Also, very important..... be sure to place a stopper over the test tubes if they are to stay overnight, because some of the water can evaporate.