Science Laboratory Activity 4 – Middle 1st Grade Fungi Monday, June 30th List of Materials per Group • • •
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A teaspoon. A permanent marker. Active dry yeast (used in baking bread--do not use quick-rising varieties.) Sugar. Bottled water (plastic bottle). Bottle soda pop (clear soda). Bottled soda pop (cola in plastic bottle). Shake each soda bottle and let the foam settle before opening, or open and allow it to go flat overnight. Both bottles must have the same initial volume. Identical round, thin latex balloons--"water balloons" are slow to expand. Non-Mylar® "helium-quality" balloons give good results. Rubber bands. Ruler to measure.
Directions for growing yeast •
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Label each bottle with the group number and contents, to keep track of each bottle: control, treatment 1 (water with sugar) and treatment 2 (dark cola drink), treatment 3 (clear soda drink). Colour is not a reliable means of identification, the caramel colour used in cola is a carbohydrate and the yeast can eat it. Put a teaspoon of dried yeast in each bottle. Seal the bottles tightly and shake the bottle. Remove the lids and stretch a balloon over the mouth of each bottle. The balloon should fit very tightly so that the carbon dioxide does not leak into the air. If it is not tight enough, place a rubber band over the bottle’s mouth to make it a tighter fit. Place each container in a warm area out of direct sunlight where they will not be disturbed. Record the diameters of the balloons in each bottle, and the start time of the experiment for each bottle.
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One good method of measurement is to wrap a string around each bottle at its widest point, and then measure the length of the wrapped string against a ruler. Record any other things you see happening: Did the colour change? Did one balloon get a hole in it? Calculate the average diameter of the balloons in each treatment and the controls. The average is calculated by adding all the diameters of all the balloons in a treatment then dividing by the number of balloons in the treatment. Compare the results (average balloon diameters) of the experiment. A graph of the averages might help show your results.
QUESTIONNAIRE 1. Is the average of the treatments larger than the average of the controls? 2. Is the average of one treatment larger than the averages of the other treatments? 3. Is carbonated water a better control than non-carbonated water in experiments with different kinds of soda pop? 4. Is the amount of sugar used in a bottle related to the amount of carbon dioxide released into the balloon? Hint: graph sugar concentration versus average balloon size.