Making Petri Dishes

Ingredients:

• 2 Petri Dishes (provided),
• Agar (provided) (enough to make 6 Petri dishes.  You only have two Petri dishes so you can repeat the experiments 3 times)
• Pot to boil liquid
• Stove
• Glass cup
• Adult Supervisor

What to do:

1. Clean Petri dishes with soapy water and allow them to dry.
2. Put 1 tablespoon water with the 2 teaspoon of  agar in a pot to boil
3. Put the pot on the stovetop and heat on low.  Stir until most ingredients have dissolved 
4. Pour half the liquid into one Petri dishes and the other half into the other Petri dish.
5. Put on the lid and let set on table to cool. Do not touch the agar.
6. After the agar solidifies you can store them in the refrigerator upside down until they are ready for use.

Experiment

Ingredients 

• Petri Dishes
• Masking tape
• Liquids like tap water, milk, pond water, or raw chicken juices
• Plastic transfer pipet (Item SS-08)
• Adult Supervisor

What to do:

1. Take a Petri dish and pick a liquid to test.  Make sure to put a piece of masking tape on the outside of the Petri dish and write the name of the liquid you are putting inside that dish on that masking tape.  Try milk, pond water, or the liquid found in package of raw chicken. 
2. Take a drop of each liquid place one drop in about five different spots on the Petri dish. Make sure to get the spots as far away from each other as possible. 
3. Put the lid back onto the dish and lay the Petri dish flat on the table and spin the dish on the table several times.  This will help the liquid spot spread out.
4. Add a drop of soap to one location.
5. Flip these Petri dishes upside down, and leave in a warm, dark place for several days.
6. You can take your forceps and pull some bacteria off and make a wet mount if you have a My First Lab Microscope.
7. After you are done use a household disinfectant and thoroughly spray the uncovered dishes.  Let these sit still for a couple minutes and then you can cover them and throw them away or clean the agar out and reuse the Petri dishes.