Thinking & Working Like A Scientist

8th Grade

What characterizes science and its methods?

Science- is the investigation and exploration of natural events and of the new information that results from those investigations.

Scientists ask, “What is there? How does it work? How did it come to be this way?

The joy of science is in the freedom to explore and wonder

Science relies on evidence and creativity

Science explanations are evaluated by testing and using evidence. Explanations that don’t fit evidence are rejected or modified and tested again

Science claims are subject to peer review and replication. Scientists attempt to identify alternate explanations to get closest to the truth

There is NO one “Scientific Method”! Scientists continually make observations, question, and form multiple hypotheses.

http://evolution.berkeley.edu/evosite/nature/IIprocess3.shtml

Science never “proves.” Hypotheses are either “supported” or “not supported” by the data collected.

Different fields of science use various methods to develop a scientific explanation.

Physicists

Biologi

st

Volcanologist

Geologists

Chemists

Scientific Inquiry

When scientists conduct scientific investigations, they use scientific inquiry.

Scientific inquiry- a process that uses a variety of skills and tools to answer questions.

Scientists begin scientific inquiry with making observations and inferences

Empirical evidence is the cumulative body of observations of a natural phenomenon on which scientific explanations are based.

Observation Inference

The act of using one or more of your senses to gather information and taking note of what occurs.

Qualitative: Things you use your 5 senses to observe. What you see, feel, smell, taste, hear. Not expressed as a number and open to interpretation.

Quantitative: Measureable observations. Length, width, height, mass, large, heavy, etc.(Expressed as a number)

A logical explanation of an observation that is drawn from prior knowledge or experience

Example: Students who study for tests earn better scores!

Observation vs. Inference

A. THE SOLUTION’S TEMPERATURE IS 27DEGREES CELSIUS

B. THE SOLUTION IS BLUE

C. THE SOLUTION HAS A BAD ODOR

D. THE SOLUTION HAS A SOUR TASTE.

What is an example of a quantitative observation?

Question or Problem

What are you trying to find out?Also called the PurposeStated in the form of a question.

Hypothesis

Hypothesis-a possible explanation for an observation that can be tested by scientific investigations

It is based on research and previous knowledge

Often used to make a prediction which is a statement of what will happen next in a sequence of events. “If______ Then “ statement.

Ex: If the soil is fertilized, then the growth rate of the tomatoes will increase.

Testing a Hypothesis

Scientists test a hypothesis by doing one or more of these steps:

Designing a controlled experiment Make a model Gather and evaluate evidence or research Collecting Data/Record Observations

Designing a Controlled Experiment

To design a controlled experiment, scientists identify factors that might affect the outcome of the experiment.

Any factor that has more than one value is called a variable.

Types of Variables

Independent variable: The thing you are testing. The one and only variable you allow to change.

Dependent Variable: What you measure to compare the results of your test. Should be able to be charted or graphed.

Constant: The variables that you don’t allow to change. What stays the same in each test.

Control: Used for comparison

A. THE THINGS THAT STAY THE SAME FROM TEST A TO TEST B TO TEST C.

B. THE VARIABLE THAT IS CHANGED FROM TEST A TO TEST B TO TEST C.

C. THE THING THAT NEVER CHANGES

D. THE THING THAT YOU MEASURE

Which of these answers best describes a dependent variable?

 

Writing Response

Microwave MiraclePatrick believes that fish that eat food exposed to microwaves will become smarter and would be able to swim through a maze faster. He decides to perform an experiment by placing fish food in a microwave for 20 seconds. He has the fish swim through a maze and records the time it takes for each one to make it to the end. He feeds the special food to 10 fish and gives regular food to 10 others. After 1 week, he has the fish swim through the maze again and records the times foreach.

What was Patrick’s hypothesis? Which fish are in the control group? What is the independent variable? What is the dependent variable? Look at the results in the charts.

What should Patrick’s conclusion be?

Procedures

Step by step instructions for how to conduct the testing.

Should be detailed enough that someone else could follow them and do exactly what you did.(Replication)

The experiment should be repeated at least five times for valid results. (Repetition)

REPLICATION VS. REPETION

Trial Number

Height after 5 Days (cm)

1 30

2 31

3 30

4 30.5

5 31

AVE 30.5

Dr. Square copied Dr. Groovy’s procedure and got similar results! The plants grew an average of 30 cm in 5 days!

If scientific explanations are replicable, they are more valid and reliable.

Table 1: Plant Growth with TurboGro by Trial

Replication (by others) Repetition (multiple trials)

Recording Data

Very careful record keeping is essential for valid results.

Use charts or tables to organize data.Records measurements as well as

observations and things you want to remember about what happened.

Analyze the Results

What are your results? What does the data show?

Create charts, tables, and graphs to represent all of your data.

Perform any calculations that will help you determine what the results mean. (i.e. averages, percentages, totals)

What are the possible sources of error? (i.e. inaccurate measurements, contamination, etc.)

Draw Conclusions

Scientists draw conclusions based on relationships among their data; a conclusion is a summary of the information gained from testing a hypothesis.

What is the answer to your Question based on your results?

Was your hypothesis supported by your experimental results? Why or why not?

If you could do this experiment over again what would you do differently next time?

What other experiments could you do to further test this?

Your results are not valid if . . .

They are based on opinions rather than data.You draw conclusions that don’t logically

follow the evidence.Your sample size is too small or is biased.

Recheck and Repeat! Then . . . .

Check all the calculations and instruments used to measure.

Repeat experiment at least 5 times.

Start questioning again . . . . Why??

Revise your hypothesis and start experimenting again!

What do I do if my hypothesis is not supported by my experimental results?

RESULTS OF SCIENCE

A scientific investigation can result in: New technology-practical use of scientific knowledge,

especially for industrial or commercial use. New materials, such as those developed New explanations as to why or how something occurs

Models

A Model is a representation of an object, process, system, or event that is similar to the original object or idea.

They scientists better understand objects/ideas; allow hands-on contact with matter that is too small, too large, too far away, too dangerous, or too expensive to build

Models can be: Physical/visual Conceptual Mathematical

MODEL BENEFITS & LIMITATIONS

Benefits•Used to study matter that is too large, too small, too far away, too dangerous, or too expensive to study directly•Models can be physical, mathematical, computer simulations, or conceptual•Can be used to make predictions

Limitations•May lack details•May not be composed of the original material (model of the Sun)•May not be able to demonstrate every aspect of the system

Not all scientific knowledge is derived from experimentationExperiment – involves identification and control of variables Independent variable/test variable/manipulated

variable Dependent variable/outcome variable/responding

variable Controlled variables

Field Study – observe a natural habitat without manipulating variables

Simulation – imitating a real situation or process

EXPERIMENT VS. OTHER FORMS OF SCIENTIFIC INVESTIGATION

Theories and Laws

SCIENTIFIC THEORY vs. SCIENTIFIC LAWS

THEORY• Evidence-based

explanation based on observations of events

• Tested and supported with multiple lines of evidence

• Widely accepted and strongly supported by the scientific community

• Can be used to make predictions

• Can be modified if new evidence becomes available

LAW• Patterns in nature derived from

scientific fact

• Describe how the natural world behaves under certain conditions

• Describes an event but it does NOT explain it!

• Can be expressed as a mathematical equation

Theories explain WHY

something happens

Laws describe WHAT happens

EXAMPLES OF SCIENTIFIC THEORIES

Theory of Evolution-All life on Earth shares a common ancestor. There is “decent with modification.”

Evidence – Fossil Record, Genetic Studies, Radiometric Dating, Stratigraphy

Theory of Plate TectonicsEvidence – Sea Floor Spreading, distribution of earthquakes and volcanoes, Fossils

EXAMPLES OF SCIENTIFIC LAWS

Newton’s Laws of Motion

Universal Law of Gravity

Law of Conservation of Energy

Law of Conservation of Mass

A. SCIENTIFIC THEORIES EXPLAIN WHY SOMETHING HAPPENS, AND SCIENTIFIC LAWS DESCRIBE WHAT HAPPENS.

B. SCIENTIFIC THEORIES REQUIRE SCIENTIFIC EVIDENCE AND SCIENTIFIC LAWS DO NOT.

C. SCIENTIFIC THEORIES ARE BASED ON OBSERVATION, AND SCIENTIFIC LAWS ARE BASED ON OPINIONS.

D. SCIENTIFIC LAWS ARE FREQUENTLY MODIFIED, BUT SCIENTIFIC THEORIES ARE RARELY CHANGED AS NEW INFORMATION BECOMES AVAILABLE.

What is the difference between a scientific theory and a scientific law?

Remember…Scientific knowledge can change as new evidence or interpretations arise

Theories may be modified, but are rarely discarded

It was a widely held belief that the Earth was the center of the Universe until the 1500s