Science fair Lab Report

Essay by chloe_blackJunior High, 8th gradeA+, November 2006

download word file, 5 pages 3.0


I chose to do this project because I thought it would be interesting to know how many bacteria there are on things you touch. Since we couldn't do hands Laura and I decided to test door handles because that is what people touch a lot. My research showed that this experiment is feasible in school settings, however it might be dangerous and requires particular care.

Independent Variable: Door handles

Dependent Variable: Amount of bacteria

Control Variables: Volume of agar, size of the Petri dishes, temperature.

Research question: What is the amount of bacteria on different door handles?


The outside handle of the bathroom will have most bacteria because when people go into the bathroom they usually want to wash their hands, which means their hands are dirty and when they touch the handle it will get bacteria from their hands.


15 Petri dishes were prepared by pouring Agar into them.

Then, samples from 4 door handles (bathroom outside, bathroom inside, refrigerator, and classroom) using sterile cotton swabs were taken. Next, the samples were put into the Petri dishes by opening the Petri dish and quickly swabbing over it. For each door handle 3 Petri dishes were swabbed. The three remaining Petri dishes were the control ones. Nothing needed to be done to them. Each Petri dish was taped, closed and labeled. Next they were put in a box and left there for 3 days. The amount of bacteria grown was checked every day from day 3, at lunch time. That was done for 4 days by seeing how much bacteria there was comparing to 1cm2. That was seen by copying the picture of the Petri dish on a plastic sheet using a permanent marker, and measuring it with a ruler. The dishes were carefully...