Gloria D. Latta
Wheaton-Warrenville South High
Type of entry
Type of activity
What question does this activity help students to answer?
How HIV spreads through a population.
Notes for teacher
Phenolphthalein is an indicator which turns pink in the presence of a base.
Required of students
Knowledge of viruses, virus replication, what HIV is, how it is contracted and how to avoid it.
Class time needed
One 50 minute class period
Abstract of Activity
Students use themselves as models to illustrate how quickly HIV can spread through a population.
Clean test tube for each student
NaOH - 0.1 Molar
Test tube rack
Fill a classroom set of test tubes 1/2 full of water. Replace one of the test tubes with .1 Molar NaOH. Pass the test tube rack around the classroom making sure each student gets a test tube of fluid. The students should not know which tube contains the NaOH. The students simulate sexual contact by exchanging fluid between the two test tubes. The number of “sexual encounters” should depend on the size of your classroom. For a class of 28, I have each student exchange 5 or 6 times. Students should not segregate themselves in their own corner of the room or exchange only with close friends. To test for HIV, the teacher goes around the room and adds a drop of phenolphthalein to each test tube. If the fluid turns pink that individual is infected. Students become very emotional when their subject or partners are found to be HIV positive!
I then see if the class can figure out who the original person was with HIV. There are a few different ways they can do this and I do not say a thing until they are done. This requires the entire class to discuss cooperatively together, each taking turns (they can narrow it down to two individuals and it usually takes between 5 and 10 minutes).
I have found it interesting to repeat the exercise by cutting their sexual encounters by half and noticing the dramatic decrease in the number of individuals who contract HIV. This leads the class in a variety of discussions!
Method of Evaluation/Assessment
Classroom discussions and journaling.
Extension/Reinforcement/ Additional Ideas
In cooperative groups, students could role play various young people infected with HIV, identify values and make decisions based on ethical principles of human dignity, beneficence and justice.
Students could produce a skit, puppet show, or story to present HIV information to younger children.