Scientific Method A logical sequence of tasks scientists use to solve a problem or answer a question

Step 1: Ask a Question This may begin as an inquiry based on another scientist’s research, an observation of your surroundings, or just plain curiosity! For example: Why does my mom add salt to water when she is waiting for it to boil? The important thing is not to stop questioning. Curiosity has its own reason for existing. – Albert Einstein

Step 2: Do Background Research Research experiments that have already been done, gather all knowledge on the subject, consult with others who have done similar research. For example: Look up the properties of water and the properties of salt, ask mom, “Does adding salt make the water boil faster?, etc…

Step 3: Formulate a Hypothesis A well developed hypothesis –is written as an “if…, then…” statement –is a measurable statement –is an educated guess –Is testable For example: If I add varying amounts of salt to water, then it will raise the water’s boiling point.

Step 4: Design and Carry out an Experiment A valid experimental design must have the following … –Independent variable –Dependent variable –Constant variables –A control –Yield same repeated results

Independent Variable The variable manipulated/ changed by the experimenter What is the independent variable in the following? The more salt I add to water, the raise the boiling point.

the AMOUNT of salt

Dependent Variable The variable that “depends” on the independent variable. What is the dependent variable in the following? The more salt I add to water, the raise the boiling point. Hint: What depends on the amount of salt?

the boiling point

Constant Variables The variables that are held constant. They do not change throughout the experiment. Necessary for the experiment to yield valid results. What variables should be held constant so that we know the change in boiling point of water is only a result of the amount of salt added, and not a result of any other factor?

Keep the same… amount of water source of water heat source thermometer type of salt thermometer reader

A Control Used as a standard for comparison. Does not receive the independent variable. What is the control for our Salt and Boiling Point Lab?

The boiling point of water WITHOUT any salt in it. Standard B.P. of H 2 O = 100 o C (212 o F)

Repeated Results The more times you can carry out your experiment (following your step by step procedure) and yield the same results, the more valid your experimental design. Experiment Results

Step 5: Collect and Analyze Data Data can be… –Quantitative A quantity Numerical Measurements –Qualitative Words Descriptions Observations Interviews Explanations Data can be organized to easily view trends. Line graph (plotted over time) Bar graph Pictography Pie graph Chart, Diagram or table Rules for Graphing Data Independent Variable is on X-axis Dependent Variable is on Y-axis

Example Bar Graph X-axis - Independent Variable - Amount of Salt Added (g) What should be written down this side? 10 g20 g30 g40 g

Step 6: Draw a Conclusion Conclusions should… –include references to your observations and data collected. –Refer back to formulated hypothesis –be unbiased: Do not try to make your data prove your hypothesis if it does not. –state what you learned, whether or not you will redesign or repeat the experiment and why.

Step 7: Publish Results Results can be published in a scientific journal for other scientists to view. Publishing experiments allows for scientists to share and build knowledge. Repeated experiments yielding the same results may lead to a Scientific Theory or a Scientific Law.

THEORY supported by many experiments explains why experiments give certain results modified as necessary

SCIENTIFIC LAW a concise statement that summarizes the results of many observations and experiments No exceptions to it Examples: Newton’s 3 Laws of Motion Law of Conservation of Mass