The Nature of Science  Scientific Method  Experimental Design

Vocabulary  Hypothesis - testable prediction  Theory - explanation of “why”  based on many observations & experimental results (example: Theory of Plate Tectoics)  Scientific Law - prediction of “what”  describes a pattern in nature (example: Gravity)

Scientific Method Theories and laws are well-accepted by scientists, but... They are revised when new information is discovered. THEY ARE NOT SET IN STONE!

Scientific Method 1. Determine the problem (question). 2. Make a hypothesis. (Usually an If/Then statement) 3. Test your hypothesis. 4. Analyze the results. 5. Draw conclusions. 6. Share your findings.

Experimental Design  Experiment - organized procedure for testing a hypothesis  Key Components:  Control - standard for comparison (background conditions) / there isn’t always a control  Single variable - keep other factors constant  Repeated trials - for reliability (sample size)

Types of Variables  Independent Variable  adjusted by the experimenter  what “ I the scientist change”  Dependent Variable  changes in response to the independent variable  what you measure

Normally plants are watered with tap water, but a student wanted to see if plants would grow better with well water. She gave 5 plants tap water every day for 2 weeks and she gave a second set of 5 plants well water for 2 weeks. At the end of the experiment, the plants that were given well water grew twice as much as the plants given tap water. The independent variable? The dependent variable? What is the control (background) group? What is the sample size?

Experimental Design I normally keep my popcorn kernels in the cupboard, but I heard on Rachel Ray that if I store them in the freezer, they will pop better…..  Hypothesis: If……, Then…….  Design your experiment: 1.What is the independent variable? 2.What is the dependent variable? 3.Which is your control group? 4.Which is your experimental group? 5.What things should be kept constant in order to only test one variable?

Presenting Scientific Data  Scientists need a way to organize their data to make it easier to observe patterns or trends. 2 common ways:  Graphs (charts)  Data Tables Must always use same unit of measure within chart or graph or data is meaningless.

Summary & Guiding Questions  Time to write your 3-5 sentence summary of your notes….  Don’t forget to write and answer your 3 guiding questions.