1. When a piece of paper is wet with water, it tears off easily. But the same paper if soaked in oil doesn’t lose strength. Why?

Experiment #1

Question: Does penicillin prevent infection?

Hypothesis: If the medicine prevents infection, than the medicine will prevent the growth of bacteria that cause infection.

Experiment: Leo placed two circles of paper in a 500 Petri dish (something used for growing bacteria).In 250 dishes, the paper was soaked with Peniccilin solution and then inoculated with bacteria. The other 250 dishes were soaked in water only and inoculated with same bacteria .All other conditions including light and temperature remained the same. After 48 hours, Leo observed all dishes and noticed there was no bacteria growth in the penicillin dishes a circle. All dishes with water only had large colonies of bacteria growing in them.

　

At the end of the experiment, a circle with a radius of 2cm formed around the circle of paper soaked in penicillin. There were no bacteria growing in the 2cm circle. No change had occurred around the other circle of paper. The bacteria were growing well.

A. What was the independent variable? ______________________________________________________

B. What was the dependent variable? ________________________________________________________

C. What was the control? _____________

　

D. What was the constant

　

E. What type of study is this? Explain

Experiment #1

Question: Does penicillin prevent infection?

Hypothesis: If the medicine prevents infection, than the medicine will prevent the growth of bacteria that cause infection.

Experiment: Leo placed two circles of paper in a 500 Petri dish (something used for growing bacteria).In 250 dishes, the paper was soaked with Peniccilin solution and then inoculated with bacteria. The other 250 dishes were soaked in water only and inoculated with same bacteria .All other conditions including light and temperature remained the same. After 48 hours, Leo observed all dishes and noticed there was no bacteria growth in the penicillin dishes a circle. All dishes with water only had large colonies of bacteria growing in them.

　

At the end of the experiment, a circle with a radius of 2cm formed around the circle of paper soaked in penicillin. There were no bacteria growing in the 2cm circle. No change had occurred around the other circle of paper. The bacteria were growing well.

A. What was the independent variable? ______________________________________________________

B. What was the dependent variable? ________________________________________________________

C. What was the control? _____________

　

D. What was the constant

　

E. What type of study is this? Explain

experiment procedure

1. Label two of the 250 mL beakers as Soaked: Pinto and Soaked:Kidney.
2. Fill each beaker with 200 mL water.
3. Count and transfer 50 pinto beans into the Soaked: Pinto beaker.Then, count and transfer 50 kidney
beans into the Soaked: Kidney beaker. Allow the beakers to rest for24 hours.
4. After 24 hours have passed, carefully strain the water from eachbeaker.
5. Place two paper towels on a flat work surface. Use the permanentmarker to label one paper towel as Soaked: Pinto and the second asSoaked: Kidney.
6. Pour the soaked beans onto paper towels, keeping them sorted bybean type.
7. Label the remaining beakers as Dry: Pinto, No Pinto, Dry:Kidney, and No Kidney.
8. Place several layers of moist paper towels at the bottom of allsix, 250 mL beakers.
9. Place 50 pre-soaked pinto beans into the Soaked: Pinto beaker,50 unsoaked pinto beans into the Dry:
Pinto beaker, and no beans into the No Pinto beaker.
10. Place 50 pre-soaked kidney beans into the Soaked: Kidney, 50unsoaked kidney beans into the Dry: Kid-
ney beaker, and no beans into the No Kidney beaker.
11. Dispense four mL of bromothymol blue solution into
each of the six measuring cups. Then, place one cup
inside each beaker (Figure 5).
12. Stretch Parafilm