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Exploring Scientific Procedures

Exploring Scientific Procedures. What is a Variable?. Simply, something that varies, or changes. Specifically, variables represent objects or conditions that can be changed, controlled or measured in an experiment. What is a constant?

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Exploring Scientific Procedures

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  1. Exploring Scientific Procedures

  2. What is a Variable? • Simply, something that varies, or changes. • Specifically, variables represent objects or conditions that can be changed, controlled or measured in an experiment. What is a constant? • Constant: does not vary, or change. A variable that does not change is a constant.

  3. Independent Variables • These variables are ones that are more or less controlled. • These are the ones that YOU choose to set up before the experiment. • Scientists manipulate these variables as they see fit. • They can be thought of as the “cause” in the experiment.

  4. Dependent Variables • Dependent variables are not controlled or manipulated in any way, but instead are responses to the independent variables. They are simply measured or recorded. • These vary in relation to the independent variables, and while results can be predicted, the data is always measured. • There can be any number of dependent variables, but usually there is one to isolate reason for variation.

  5. Chosen intentionally (“I” changed it) Controlled (I.M. Independent = manipulated) Vary at known rate Cause Intentionally left alone (“D”ata taken). Measured Vary at unknown rate Effect Independent V. Dependent The DEPENDENT variable depends on the INDEPENDENT variable… it is measured later.

  6. Example: How does temperature affect the evaporation rate of water ? Variables: • Temperature • Evaporation rate Can you indentify the dependent and independent variables? Are there any controls?

  7. Graphing Dependent v. Independent Variables • The dependent variable is placed on the y-axis, while the independent variable is placed on the x-axis. • Example: temperature effect on evaporation rate of water. Evaporation rate (mm/hour) Temperature (Celsius)

  8. The INDEPENDENT VARIABLE and the DEPENDENT VARIABLE can be found throughout the following steps of scientific inquiry:QUESTIONSHYPOTHESISDATA TABLESand GRAPHS

  9. Problem Statement: Does the _________________________ (Independent Variable) affect the ________________________?(Dependent Variable) All scientific experiments begin with simple questions….

  10. A Hypothesis is an educated guess about what you think the relationship is: • If the_____________is_____________, • (Independent Variable)(increased/decreased) • then the_____________will___________. • (Dependent Variable) (increase/decrease)

  11. All data that is collected within an experiment must be in an easy format for future study... The following DATA TABLE is an example of a well-organized table.

  12. Data Table Dependent Variable Independent Variable Trial One TrialTwo Trial Three Average

  13. While analyzing the data in an experiment, you are typically looking for patterns and relationships between what you are changing (the INDEPENDENT VARIABLE)and your data(the DEPENDENT VARIABLE). A GRAPH can help visualize the data in a way that is easier to see any of these possible relationships.

  14. GRAPHS: Graph Title Dependent Variable Independent Variable

  15. The TITLE of any GRAPH should include both VARIABLES of the experiment…. ….this helps the person who is reading your graph to easily identify what the data is all about!!!

  16. GRAPH TITLES The effect of the________________ (Independent Variable) on the_________________. (Dependent Variable)

  17. Remember.. You must see the INDEPENDENT VARIABLE and the DEPENDENT VARIABLE in theQUESTIONSHYPOTHESISDATA TABLESand GRAPHS!!!

  18. Let’s try an example... Question: Does the distance a rubber band is pulled back affect the distance a rubber band can travel?

  19. Does the distance a rubber band is pulled back affect the distance a rubber band can travel? Can you identify the IV and DV? IV = Distance a rubber band is pulled back DV = Distance a rubber band can travel

  20. WHAT WOULD BE YOUR HYPOTHESIS FOR THIS QUESTION?

  21. If the distance a rubber band is pulled back is increased, then the distance the rubber band can travel will increase. Hypothesis

  22. HOW WOULD YOU FILL OUT A DATA TABLE?

  23. Data Table Distance a rubber band is pulled back (IV) Distance the rubber band can travel (DV) Trial One Trial Two Trial Three Average 1 cm 2 cm 3 cm

  24. HOWABOUT A GRAPH ?

  25. The effect of the distance a rubber band is pulled back on the distance the rubber band can travel Distance the rubber band can travel(cm) (DV) Distance a rubber band is pulled back (cm) (IV)

  26. The variables “distance a rubber band is pulled back” and “distance a rubber band can travel” can be seen throughout the entire experiment!!!

  27. Remember: All other variables in an experiment must remain CONSTANT . Any possible changes in materials or procedure are sources of error (SOE) that could alter the results of an experiment. Constants are very important because you only want to change ONE variable in your experiment!!!

  28. Why do you only want to change ONE thing in your experiment? So that you can identify what variable is altering the results in your experiment….. ….if you changed two variables, how would you know which one is affecting the results???

  29. CONSTANTS share their importance with another factor in many experiments... The CONTROL The CONTROL is the normal expectation of what is to happen and is used for comparison. It is used to identify possible sources of error in the experiment. For example...

  30. If you wish to see the effects of salt water on the growth rate of plants, the CONTROL in this experiment would be to use ordinary water with their plants to gauge the normal growth rate. Along with this CONTROL, the student will grow other plants with varying levels of salt water...

  31. If all the plants die, with the exception of the CONTROL, you may assume that the salt is the culprit!!! If even the CONTROL perishes, you may have an unknown SOE in the water that needs to be identified.

  32. The End

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