Science Science and the and the

Scientific Scientific MethodMethod

Long Ago

• Until 1859 the common belief was that life could appear from non-living things.

• This was called spontaneous generation.

• The Slow Death of Spontaneous Generation occurred from 1668 to 1859.

• ?What is spontaneous generation?

OBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat.

HYPOTHESIS: Flies produce maggots.PROCEDURE

Controlled Variables:jars, type of meat,location, temperature,time

Independent Variables:gauze covering thatkeeps flies away from meat

Uncovered jars Covered jars

Several days pass

Maggots appear No maggots appearDependent Variable: whether maggots appear

CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous generation of maggots did not occur.

Section 1-2

Redi’s Experiment on Spontaneous Generation (1668)

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John Needham (1745)• Everyone knew that boiling killed microorganisms (common

knowledge)• John Needham proposed to test whether or not microorganisms

appeared spontaneously after boiling.• He tried to disprove Redi’s conclusion– He boiled chicken broth, – put it into a flask, – sealed it, – and waited • sure enough, microorganisms grew. Needham claimed victory for

spontaneous generation. • ?Do you see a problem with this experiment?

Spallanzani

• “You missed a variable, for life to be generated you need contact with the air”

• Is this true?

Gravy is boiled. Flask isopen.

Gravy is teeming with microorganisms.

Gravy is boiled. Flask issealed.

Gravy is free of microorganisms.

Section 1-2

Figure 1-10 Spallanzani’s Experiment

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?What is the difference between Needham’s Experiment and Spallanzani’s Experiment?

Broth is boiled. Broth is free ofmicroorganismsfor a year.

Curved neckis removed.

Broth is teeming with microorganisms.

Section 1-2

Figure 1-11 Pasteur’s Experiment

Go to Section:

?How is Pasteur’s experiment different from Spallanzani’s?

?When did the microorganisms begin to grow in Pasteur’s experiment?

Scientific Theory• Science Theory- an explanation of a natural phenomenon that is

supported by a large body of scientific evidence obtained by many different investigations and observations.

• A theory remains valid only if every new piece of information supports it.

• If available information does not support a theory, then the theory is disproved. 

• New discoveries in science occasionally change a theory.• ?Can a theory change and, if it does, how?

• Scientific Law- facts of nature that are generally known to be true. Stronger than a theoryHypothesisHypothesis Theory Theory Law Law

Nature of Science

• Science never reaches “Fact”

• Constantly, new technologies and ideas arise that disprove current theories.

• Science gets as close to “Fact” as possible as people fail to disprove a concept.

• ?Why does science never reach “fact”?

Recipe for Bees About 2000 years ago, a Roman poet wrote these directions for producing bees.

Is this science and is this an experiment?

Yes!At the time with the current knowledge this could be repeated and have a similar result

What IsThe Goal of Science• To investigate and

understand nature

• To explain events in nature

• To use those explanations to make useful predictions

Scientific Method1. Problem2. Research3. Hypothesis4. Experiment5. Analysis6. Conclusion

• Independent Variable is the amount of sugar.

• Dependent variable was density we wanted to see if water would float.

• Control the water• Constant: The amount of water, dye,

spoons, cups, test tubes, temp,• Procedure:Mixed measured water, sugar

with water, dye then we put it in a test tube.

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• Then put food coloring in the other water then, tilted test tube poured in the water inside the tube and tested it to see if it would float.

• Results Water can float on a sugar solution.

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Scientific Method

• Identify the Problem – predict outcome?

• Form a Hypothesis

• Set Up a Controlled Experiment

• Record and Analyze Results

• Draw a Conclusion

• Repeat and Retest – magic # is 3 of same! 

Vocabulary

• Hypothesis – A prediction about a possible answer to a scientific question.

• What will happen to the independent variable and the dependent variable during the expermiment.

• The plant is dying because it needs to be watered. It is a statement which is

an educated guess and it is testable

Vocabulary

• Independent variable – The variable you the scientist change in an experimental group.

• Cause• Often graphed on the X-

Axis

Vocabulary

• Dependent variable – Part of the experiment that a scientist wants to observe and measure.

• You do not have direct control over the results of this variable.

• Effect• Graphed on the Y-Axis• Example:How low did the blood sugar

drop?19

Vocabulary

• Experimental group – In an experiment this is the group that the independent variable IS given to. It is compared to the control group.

Experimental Group: Plant A

(watered)

Control Group: Plant B is left the same (not watered)

Vocabulary

• Control group • the group that is used compare your results• this is the group you do NOT give your

independent variable.• Often is give the Placebo (FAKE PILL)

Controls are needed to eliminate other explanations of experimental results. For example, suppose a researcher feeds an experimental artificial sweetener to thirty laboratory rats and observes that eight of them die of dehydration.

Can we determine without doubt that the artificial sweetener killed them?

The underlying cause of death could be the sweetener itself or something unrelated.

Vocabulary

• Independent variable – Part of the experiment that a scientist purposely changes; also known as manipulated variable

• Dependent variable – Part of the experiment that a scientist wants to observe, which may change in response to the manipulated variable; also known as a responding variable. You do not have direct control over this variable.

• Controlled variable- All the variables that are kept the same (held constant during the entire experiment.

DR. S Insulin Pill

Patient Start Blood SugarLevel

Final Blood Sugar Level

Student 1 185 125

Student 2 184 184

Student 3 185 185

Student 4 186 124

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The Effect of Fertilizer on Plant Growth• Question: Will fertilizer increase plant

growth?• Hypothesis:• Materials: Tomato seeds, Water, Flower pots• Miracle Grow fertilizer• Variables: • Independent Variable:• Dependent Variable:• Control:• Constants: 24

Results

Plant Day 11 Day 12 Day13 Day 14

Control 1 0 cm 0 cm .25 cm 1.0 cm

Control 2 O cm 0 cm .75 cm 1.1 cm

Fertilizer 1 .5 cm 1.4 cm 4.9 cm 5.9 cm

Fertilizer 2 1.0 cm 1.8 cm 4.5 cm 5.8 cm

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• Results:

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Vocabulary

• Controlled experiment – a test of the effect of a single variable keeping all other variables the same.

• Change “only one variable” in an controlled experiment

• Variable – anything that you change or changes as a result of what you do

Vocabulary

• Dependent variable – Part of the experiment that a scientist wants to observe, which may change in response to the manipulated variable; also known as a responding variable. You do not have direct control over this variable.

Die

Live

Why is the dependent variable referred to as “The Effect”?

The dependent variable is dependant on the independent variable

• I want to know if more light would cause hens to lay more eggs.

• In this experiment, what would be the only thing (variable) I would want to change?

• Why would I not want to also change the amount of food I give them?

Explaining the evidence

• Hypothesis- a statement that is a possible explanation for a set of observations or answers to a scientific questionA hypothesis must be testable. (not useful if it

can’t be tested)

Vocabulary

• Experiment:• Data collection – collection of evidence;

inform• Data Analysis – Make a graph from the

information gathered from observations

Vocabulary

• Observation - use of one or more of the senses—sight, hearing, touch, smell, and sometimes taste—to gather information

– Qualitative observations involve characteristics that cannot be easily measured or counted. These are descriptions.

– Quantitative observations involve numbers

Vocabulary

• Data analysis - Observing your data, picking out the important results, and making sense of the data.

• Graphs are very useful in analyzing data

• Data is anything collected through observation in an experiment

A few types of graphs

• Line Graph

• Bar Graph

• Pie Chart

There are times where one graph is far better than the others

Vocabulary

• Inference - logical interpretation based on prior knowledge and experience

• For example, researchers might test small quantities, or samples, of water from a reservoir. If samples collected from different parts of the reservoir are all clean enough to drink, the researchers may infer that all the water in the reservoir is safe to drink.

Vocabulary

• Conclusion - Using the evidence of an experiment to determine whether the hypothesis was supported or refuted (wrong).

State the Problem

Scientific M

ethod

It Stinks!

Form a Hypothesis

• The room stinks because a rat died in a cabinet

• The room stinks because someone passed gas

– Pick only one hypothesis to test, you can come back to the others if you conclude the first one is wrong.

– Pick the most likely hypothesis to test first

Scientific M

ethod

Set Up a Controlled Experiment

• Have a control to compare your results to- in this case the room before to odor

• Only Change One Variable– The variable changed must make sense– I will turn on the exhaust and see if it still

smells bad 5 minutes later– If it does not smell bad it was only something

temporary

Scientific M

ethod

Record and Analyze Results

• It still smells bad after 5 minutes

Scientific M

ethod

Draw a Conclusion

• My Hypothesis about the flatulence was incorrect go back to step one and test another hypothesis

Scientific M

ethod

Station 3

• 1. Define abiogeneisis

• 2. What is the control variable of this experiment?

• What is the Independent variable of this experiment?

• Did li 42

Station 2

• What did Louis Pasteur discover?

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