Scientific Laws & Theories Scientific Knowledge Scientific Laws & Theories

Theory if something is said to be “just a theory,” it usually means that it is a mere guess and unproven. In scientific terms: Scientific theory implies that something has been proven and is generally accepted as being true.

Theory A THEORY: a well-supported EXPLANATION of a set of related observations or events based upon proven hypotheses and verified multiple times by different researchers. One scientist cannot create a theory; he can only create a hypothesis. (Example: Theory of Evolution)

Theory THEORIES MUST: Be supported by data Be verified by other experiments (LOTS OF TESTING) Subject to review by peers (other scientists) May be modified or expanded if additional data is found

LAWS A DESCRIPTION of a specific relationship under given conditions in the natural world. (Why do objects fall toward the earth?)

LAWS DESCRIBES the way the world works. It is generally accepted to be true based upon the fact that they have always been observed to be true. (Example: Law of Gravity)

There Are Different Forms of the Scientific Method! Science defined as a methodical approach to the acquisition of knowledge. There Are Different Forms of the Scientific Method!

use experimental forms of the may use a form of the scientific method. Physical Sciences: (physics and chemistry) use experimental forms of the "scientific method." - do experiments to gather numerical data from which relationships are derived, and conclusions are made. Descriptive sciences: (zoology and anthropology) may use a form of the scientific method. - involves gathering of information by visual observation or interviewing.

considered data, and how data is Common among all sciences is the making of hypothesis: - to explain observations - gathering of data, and based on this data - drawing of conclusions that confirm or deny the original hypothesis. The difference is in what is considered data, and how data is gathered and processed.

Data for a Physical scientist are numbers numbers are often plotted on graphs. - Graphs can be used to derive equations that can be used for making predictions. Data for an Anthropologist could be a recorded interview. - interviews can be compared to other related information.

Steps in the Scientific Method Observation Hypothesis Experiment Data Collection Conclusion Retest 13

Observations Gathered through your senses A scientist notices something in their natural world

Observations An example of an observation might be noticing that many salamanders near a pond have curved, not straight, tails

Hypothesis A suggested solution to the problem. Must be testable Written as an If…Then… statements Predicts an outcome

Hypothesis An example of a hypothesis might be that the salamanders have curved tails due to a pollutant in the moist soil where they live.

A procedure to test the hypothesis. Experiment A procedure to test the hypothesis.

Variable – factor in the experiment that is being tested

A good or “valid” experiment will only have ONE Testable variable!

Controls and Variables Control, Independent & Dependent

Scientific Experiments Follow Rules An experimenter changes one factor and observes or measures what happens.

The Control Variable The experimenter makes a special effort to keep other factors constant so that they will not affect the outcome. Those factors are called constant variables.

What is the Purpose of a Control? Controls are NOT being tested Controls are used for COMPARISON

Other Variables The factor that is changed is known as the Tested (Independent) variable. The factor that is measured or observed is called the Outcome (Dependent) variable.

Example of Controls & Variables For example, suppose you want to figure out the fastest route to walk home from school. You will try several different routes and time how long it takes you to get home by each one. Since you are only interested in finding a route that is fastest for you, you will do the walking yourself.

What are the Variables in Your Experiment? Varying the route is the independent variable The time it takes is the dependent variable Keeping the same walker throughout makes the walker a control variable.

One more thing… it is best to make several trials with each independent variable.

Valid Experiments what constitutes a valid experiment?

To be a Valid Experiment: Two groups are required --- the control & experimental There should be only one variable

Data Results of the experiment May be quantitative (numbers) or qualitative

Data Must be organized Can be organized into charts, tables, or graphs

Displaying Data Tables, charts and graphs are convenient ways to clearly show your data. Be sure to consider how to best show your results with appropriate graph forms. Be sure to give your charts and graphs an appropriate title that explains what the data measures. On line and bar graphs, the x and y axis must be appropriately labeled with correct unit of measure (in metrics where applicable). Displaying Data

Bar Graph relationships between groups. A bar graph is used to show relationships between groups. The two items being compared do not need to affect each other. It's a fast way to show big differences.

A typical chart or table for this graph might look like this: Notice how easy it is to see what was done in the experiment below with bean plant growth and different brands of fertilizer. A typical chart or table for this graph might look like this:

Line Graph A line graph is used to show continuing dependent variable. data; how one thing is affected by another. It's clear to see how things are going by the rises and falls a line graph shows. This kind of graph is needed to show the effect of an independent variable on a dependent variable.

A typical chart or table for this graph might look like this: In the sample below, the pulse rate of a person is shown to change over time. As time continues, the pulse rate changes. A typical chart or table for this graph might look like this:

Pie Chart A circle graph is used to show how a part of something relates to the whole. This kind of graph is needed to show percentages effectively

A typical chart or table for this graph might look like this: In the sample below, the preference of Ice Cream flavors determined by a survey conducted of the people of Twin Groves. A typical chart or table for this graph might look like this:

Conclusion The answer to the hypothesis is based on the data obtained from the experiment

Conclusion Should be written WITHOUT BIAS (the hypothesis may be WRONG so the experimenter must be OBJECTIVE and not try to make the experimental results come out the way they want them to); ETHICAL Should state whether the hypothesis WAS or WAS NOT supported Experiment only VALID (correct) if scientist is honest & unbiased

verify the results, experiments must be retested. In order to verify the results, experiments must be retested.

Replication vs. Repetition

Replication vs. Repetition What is repetition? conducting multiple trials of measurements or observations in a scientific investigation. YOU!!!!!

Replication vs. Repetition What is replication? the reproduction of a scientific investigation by another person or group to ensure the accuracy of an experiment. OTHERS!!!!

Replication vs. Repetition Why should experiments be replicable? All scientific investigations and experiments should be replicable (able to be replicated by other scientists) to ensure the accuracy of the investigation/experiment and the results of the investigation/experiment. Be able to compare methods (procedures) and results obtained in a scientific investigation.

Solving a Problem 1) Identify a Problem 2) State Observations about the problem 3) Form a Hypothesis about the problem (if…then…) 4) Design an Experiment to test the hypothesis 5) Collect Data 6) Form a Conclusion 7) Retest

Scientific Method Reminders: 1. All measuring is to be done accurately and consistently using metrics where applicable. 2. Keep a detailed daily record or log book for measurements, changes and problems. 3. Take photographs, make diagrams or drawings of various phases of your experiment. 4. Observations and measurements should be organized in tables or charts that are clearly labeled. 5. Results should be graphed using one of the three methods described above. 6. Don't become discouraged; work diligently and repeat an experiment, if necessary.