Bacteria and sweat
The materials required for this science project:
- 10 petri dishes prepared with agar
- 10 disinfected swabs
- 1 bottle of disinfected water
- 5 pairs of running shoes
- 5 pairs of cotton socks
- 5 participants
- 1 marker pen
1. For this science fair project, the independent variable is whether the participant wears socks or not. The dependent variable is the rate of bacteria growth in the petri dish. This is determined by measuring the size of the bacteria colony using a ruler. The constants (control variables) are the type of shoes used, the type of socks used, the length of time the participants are made to wear the shoes, the room temperature and the amount of sunlight received.
2. The 10 petri dishes that are prepared with agar are stored in a refrigerator. The petri dishes are brought to room temperature before the start of the experiment by taking them out of the refrigerator and allowing them to attain the room temperature.
3. The experiment will require 5 participants. They are each given 1 pair of shoes and only one sock. The participants are required to wear the sock on their right foot only, before wearing their shoes. The shoe on the left foot is worn without socks.
4. For the next 3 hours, the 5 participants are made to walk, jog, play games and perform other physical activities that will cause their feet to sweat. After 3 hours the shoes are collected from the participants.
5. The sterilized swab is first made damp with the sterilized water. The swab is swathed around the inside of the shoe and then rubbed all over the surface of the petri dish. The cover is closed and the petri dish marked “With socks” for the right shoe and “Without socks” for the left shoe. The petri dish is kept in a cool shaded place for the bacteria to grow.
6. The diameter of the bacteria colony is measured after 5 days and recorded in the table below.
The bacteria should be destroyed before the swabs are discarded. Pour some bleach into the petri dish to kill all the bacteria before disposing in the trash.