Understanding the Scientific Method Practice Assignment

 On a sheet of notebook paper, write the (A) title / question of each experiment.  Then identify the (B) independent variable,  (C) dependent variable,  (D) number of repeated trials,  (E) constants, and         (F) control (if present).  (G) Identify the hypothesis for the experiment.  If the hypothesis is not explicitly stated, write one for the scenario.  (H) State at least two ways to improve the experiment described in the scenario.

1.       Does the amount of water effect the growth of plants?

·            Ten seeds were planted in each of 5 pots found around the house that contained 5OO g of "Peat's Potting Soil."

·            The pots were given the following amounts of distilled water each day for 40 days: Pot 1, 50 mL; Pot 2, 100 mL; Pot 3, 150 mL, Pot 4, 200 mL; Pot 5, 250 mL.

·            Because Pot 3 received the recommended amount of water, it was used as a control.

·            The height of each plant was measured at the end of the experiment.

2.       Does color affect the food choices of children?

·         Sandy wanted to find out if the color of a food would affect whether or not kindergarten children would select it for lunch.

·         She put food coloring into 4 identical bowls of mashed potatoes.  The colors were red, green, yellow, and blue.

·         Each child chose a scoop of potatoes of the color of their choice.

·         Sandy did this experiment using 100 students.  She recorded the number of students that chose each color.

3.       How does height affect the distance that an escaping liquid will spurt?

·         Susie wondered if the height of a hole punched in the side of a quart-size milk carton would effect how far from the container different liquids would spurt when the carton was full of the liquid.

·         She used 4 identical cartons and punched the same size hole in each. The hole was placed at a different height on one side of each of the containers.

·         The height of the holes varied in increments of 5 cm, ranging from 5 cm to 20 cm from the base of the carton.

·         She put her finger over the holes and filled the cartons to a height of 25 cm with each liquid.
When each carton was filled to the proper level, she placed it in the sink and removed her finger.

·         Susie measured how far away from the carton's base the liquid had squirted when it hit the bottom of the sink.

4.       How does spacing affect the health of plants?

·         Sandy heard that plants compete for space. She decided to test this idea.

·         She bought a mixture of flower seeds and some potting soil.

·         Into each of 5 plastic cups she put the same amount of soil.

·         In the first cup she planted 2 seeds, in the second cup she planted 4 seeds, in the third cup 8 seeds, and in the fourth cup she planted 16 seeds. In the last cup she planted 32 seeds.

·         After 25 days, she determined which set of plants looked best.

5.       Which type of insulation works best?

·         Ester became interested in insulation while her parent's new house was being built. She decided to determine which insulation was best.

·         She filled each of 5 jars half-full with water. She sealed each jar with a plastic lid.

·         Then she wrapped each jar with a different kind of insulation.

·         She put the jars outside in the direct sunlight.

·         Later, she measured the temperature of the water in each jar.

Any Class

Scientific Method

Description:  Students will review/learn the parts of a scientific investigation by using the unlabeled parts of a completed investigation and putting them in the order that they think is logical, then naming them.

Materials:  Completed lab write up (see below) cut into parts and the complete lab placed in an envelope.  Each group of 3-4 students needs an envelope.  A textbook may help them name the parts.

Time Needed:  10-15 minutes for students to work, 10-15 minutes for follow-up discussion.

Previous Knowledge:  None

Procedure: 

1.  Ask students to describe what they think scientists do.  There are many possible answers.  

2.  Ask how they think scientists do what they do.  Now the answers become a little more precise. Make it clear to students that the only things all scientists must be able to do is convince other scientists that their procedures will repeatedly provide consistent data and their conclusions are reasonably drawn from their data. 

3.  Give the students their envelopes and ask them to place the pieces in the order they think would be logical for a scientific investigation.  Explain that this is based on a famous experiment (Fleming) and that the scientific names of the molds and bacteria are missing.  Students can assume that the strains of mold and bacteria were the same for each petri dish.

4.  Ask the students to name the parts, using previous knowledge or their textbooks. 

5.  As students finish, have different groups report the order they placed the pieces in and justify it. 

Scoring guide

Key to each lettered part of the investigation:

A= research question, B=materials, C=hypothesis,  D=Title, E=analysis, F=initial observation, G=procedures, H=data, I=conclusion    

C  If mold is added to bacterial plates, then bacteria will not grow

F    A collection of bacterial culture dishes were found to be contaminated with mold.   
      Everywhere the mold was growing, the bacterial colonies near the mold were dead.

A  Does the mold kill bacteria?

D   Discovering a Bacteria Killer

B  Petri plates, nutrient medium, bacterial solution, mold culture, warm place

G

1.  20 petri plates were filled with nutrient medium, covered and allowed to cool. 

2.  All plates were exposed to the bacterial culture.

3.  10 plates were also exposed to the mold.

4.  The plates were placed in a warm (25 degrees C) place for 7 days.

5.  On the 8^th day, the number of bacterial colonies were counted and recorded.

H   Plates with bacterial culture only:

E   The addition of mold to the bacterial culture seemed to significantly reduce the number
      of bacteria that can grow.  A further study of this phenomenon should include different
      types of mold and different types of bacteria.  Applications of the study to treatment of
      human disease should proceed with caution.

   Average number of colonies without mold

 

  Average number of colonies with mold

 

I   The mold predictably kills the bacteria in a petri dish.

J  How do you grow bacteria?  Where can I buy supplies? What other research
    has been done on mold and bacteria?