In order to build excitement and anticipation for our upcoming science experiment, as students enter the room I play two videos that are accessed from MovieClips - Gru's Lab from Despicable Me and It's Alive from the original Frankenstein.
After watching the videos, I explain that today is the day we will perform an experiment to help us determine whether or not handling/eating food with dirty hands actually passes more bacteria onto our food.
However, before jumping right into our experiment, we will get a little practice in how to conduct a scientific investigation.
Before conducting our actual experiment, I have the students gain some practice by performing the virtual lab, How Does Your Garden Grow?,* by Discovery Education. They also provide a super student worksheet and teacher guide that walks you and your students through the entire process. I have found that I can follow the guide without making any necessary revisions to suit the needs of my class, but you should read through it ahead of time to see what changes or "tweaks" you would like to make for yours.
I walk you through how to use this virtual lab in this short video.
*This is a great resource for you to share with your colleagues. Not only does it provide virtual labs like the one above, but their Science Fair Central site is filled with resources for science fair coordinators, teachers, students, and even parents. Not only will you find yourself referring to it for your own needs, but you will find it useful to direct others there as a key resource. Sharing this site will help to alleviate a lot of questions that you may receive as you conduct your own class or school science fair.
In order to prepare for our real experiment, I give a little background information and explain to the students that molds are microscopic fungi that live on plant or animals. Under a microscope, they look like skinny mushrooms. In many molds, the body consists of root threads that invade the food it lives on, a stalk rising above the food, and spores that form at the ends of the stalks. The visible part of the mold that appears on the surface of food - such as gray fur on bologna, fuzzy green dots on bread, white patches on Cheddar or fruits - are given that color and appearance by their spores.
While the mold that grows on food is not usually harmful (unless you have a specific mold allergy), I explain to the students to think of mold as a warning sign that harmful germs and bacteria are nearby. If the food is moldy, it is more likely to be contaminated, since mold, germs, and bacteria tend to prefer the same growing conditions and environments.
Now that we have practiced how to perform an experiment and we are more knowledgeable on the details of our own topic, it is time to conduct our investigation. I project the question, hypothesis, and procedures from the prior day's lesson on the board. We read through them carefully in order to make sure we are prepared to follow them in class.
I choose a student to use gloves to take one piece of bread from the loaf and place in in a baggie labeled, "control". We review the meaning and purpose of a control group before moving on.
Next, I have the students form a line around the circumference of room, starting at the classroom sink, then moving to a table in the center of the room, where I will have the bread ready. I select one student to be the line leader, so I am aware of when each new trial should start and end. One by one, each student comes to the table and rubs each side of the piece of bread. After touching the bread, they follow the line to the sink, so that they can wash and dry their hands before making their way back to me. Before each new round, I make sure my own hands are appropriately washed dried, and/or sanitized. The last person in each line bags the bread and labels it as "unwashed", "washed", or "washed and sanitized".
After each piece of bread has been bagged and labeled, we hang them on the white board with magnets so that we have a plain white background. This makes it easier to observe them and to notice changes over the coming days.
I select a few random science notebooks every day to check in on student progress. I want to make sure they are accurately and completely recording their observations using precise scientific vocabulary. I make sure to view each student's notebook before the process of collecting data is complete, but I also purposely repeat a few. This sends the message to the students that their notebook is "fair game" at any time, and lets them know they are accountable for their work, even if I have already looked at it in prior days. If a student has not written their observations with accurate labels, units, or information, has not provided enough detail, or has not used legible writing, I have them revise their work, using my notebook as a guide.