Ms. Rozema’s Chemistry Class (Fall 2010)

It is a method, that is used to find answers to questions about the world around us.

Only One Method? No Some versions have more steps. They all begin with the identification of a

problem or question to be answered. Our problem provides an experimental

method

Hypothesis: Testable Statement based on

observations

Data: Information gathered during an

experiment

Control: An entire experimental set-up which remains “neutral”, used for comparison.

Constant: Common/Similar parts to different experimental set-ups.

Variable: Something that changes during the experiment.

Experimental / Independent Variable: The variable you set-up and test.

Observational / Dependent Variable: The variable that you observe (the result of your test).

“To Support”: Providing lots of detailed data to convince a reader of your conclusion.Pattern: A general observation which occurs multiple times.

Conclusion: A statement which defends the accuracy of your hypothesis using data collected.

Problem / Question

Predictions & Hypothesis

Procedure

Data Analysis

New Procedure

Conclusion

Experiment

Observations use your 5 Senses to take note: An observation is taking note of what

actually happened! Observations are absolutely necessary

during data collection!

Inferences use your prior knowledge to make predictions/assumptions… An inference is taking note of what you

thought happened or why you think it happened!

Inferences are NEVER to be used during data collection, and only when writing your predictions/hypothesis!

Visual Descriptions (What did you see?): Color Shape Texture / Print / Pattern Bubbles, Steam, Condensation Size / Quantity

Problem / Question

Auditory Descriptions (What did you hear?): Fizzing Popping

Olfactory Descriptions (What did you smell?): Sweet, Sour Burnt Compare to known smells

Touch Descriptions (What did you feel?): Cold, Hot Soft, Smooth Rough, Sharp Measurements: Mass (grams), Volume (mL) Height / Length (cm)

#1)What observations can you make? (List in your table!)

What inferences could you make? (List in your table!)

#2)What observations can you make? (List in your table!)

What inferences could you make? (List in your table!)

#3) You are conducting an experiment to determine if increased ultraviolet radiation from the decrease in the ozone layer is killing off frog tadpoles. After examining all of the data available in the library, you decide to go with a hypothesis that increased ultraviolet radiation from the sun is killing off the tadpoles. You design an experiment with a control and an experimental group. Your control group (group 1) involves 100 tadpoles in a five gallon container of water, that is covered by glass (knowing that the glass will filter out the ultraviolet radiation). The experimental group (group 2) will be set up exactly like group 1, except that instead of being covered with glass, it is covered with an acrylic plexiglass, which will not filter out the U.V. radiation. You then place the groups outside for a period of a month, and observe the results.

a. What is the experimental variable and what is the dependent variable? - Experimental Variable = UV Radiation present- Dependent Variable = Ending Number of Tadpoles

a. Does the information from this experiment support the hypothesis? No

b. If no, then what might be causing the decrease in frog populations?- Changes to temperature, oxygen, food availability, mating success

c. Which is the control group, and which is the experimental group?- Control Group = Group 1 = Tadpoles without UV Radiation- Experimental Group = Group 2 = Tadpoles with UV Radiation

d. What is the difference between the 2 groups? Should they be different in any other way?UV Radiation…. No, too many variables makes it hard to conclude!

Results

Group 1 Group 2

Initial Number of Tadpoles 100 100

Ending Number of Tadpoles 96 96

#4) Niko Tinbergen (1907-1988) was a Swedish Ethologist (animal

behaviorist) famous for studying animals in their native habitats. One of his classic experiments involved a bird called the black-headed gull (Larus ridibundus). Black-headed gulls build nests of twigs on the ground and lay light brown eggs that are covered with dark brown spots. However, the inside of the egg is white in color. Tinbergen noticed that adult gulls pick up the eggshells shortly after a chick has hatched, and fly them to a location far from the nest, where they are left. Since this behavior required expending energy and time that could have been spent feeding and protecting the chicks, Tinbergen wanted to know why the birds did this.

Problem: Why do black-headed gulls remove eggshells from the nest? Hypothesis: The white interior of the shell is not camouflaged and attracts predators to the nest. Therefore, the gulls remove the shells to decrease predation. Test: Tinbergen and his co-workers collected gull eggs and painted 69 of them white and left 68 of them with their natural color. (Statistically, these numbers are close enough to be considered equal.) The researchers then scattered the eggs next to a gull breeding area and observed from a nearby blind. Predation rates were recorded for white versus natural colored eggs.

a. Do the results of this experiment support the hypothesis? Why, Why not?- Yes, the results do support his hypothesis.

b. Are you 100% sure (without a doubt) that your hypothesis is correct? - No. There may be other factors playing in, aside from camouflaging. To make sure I would request that this test be completed many more times, in different locations. - Also—His starting number is not the same, and while not a huge difference, still odd.

c. If you were working with Tinbergen, what would you suggest be done next?- I would suggest painting the eggs different colors (white, bright yellow, bright red, etc.) to test the camouflage hypothesis. - I would also suggest that we re-complete the same experiment multiple times and collect data.- I would also suggest starting with the same number of eggs!

d. Identify the experimental and dependent variables. - Experimental Variable = Egg Color - Dependent Variable = Number of Eggs Taken by Predators

Data

Original Number of Eggs

Eggs Taken by Predators

Eggs Not Taken

White Eggs 69 43 26Natural Eggs 68 13 55