1. Identifying Variables & Designing Investigations in the Scientific Method. Physical Science

2. 3 Kinds of Variables in Physical Science  Independent Variable – something that is changed by the scientist  What is tested  What is manipulated  What is controlled  Example: Ohm’s law : U = I x R  Something else?

3. 3 Kinds of Variables in Physical science  Dependent Variable – something that might be affected by the change in the independent variable  What is observed  What is measured  The data collected during the investigation

4. 3 Kinds of Variables in Physical science  Controlled Variable – a variable that is not changed  Also called constants  Allow for a “fair test”  Any example we know in Physical Science?  What about Newton’ laws?

5. Let’s look for several exa- mples for Physical Science First Example we have is in Physical science:

6. Wires of different resistances R were given the same voltage V in a closed circuit. So what is changing? The current I? Remember the formula! V = I x R.

7. Now remember the very important step in our investigation! Let’s identify the variables in this investigation.

8. What was the independent variable?  resistances of the wires  Different resistances were tested by the scientist  Remember that voltage was fixed and thus constant!  So what is changing then?  Of course, the current!

9. What was the dependent variable?  The current!  The current was observed and measured by the scientist  Again the formula of the Ohm’s law is V = I x R  V is voltage, I is current, R is resistance

10. What was a controlled variable?  Devices we used to measure:  Ampermeter  Voltmeter  Ohmmeter  Multimeter  Something else?

11. Are you getting the idea? Or not!?! Another example in the Physical Science:

12. An investigation was done with an electromagnetic system made from a battery and wire wrapped around a nail. Different sizes of nails were used. The number of paper clips the electromagnet could pick up was measured.

13. What are the variables in this investigation? Just be careful! But give your opinions!? Go! Please! Can we do it!?

14. Independent variable in Physical Science:  Sizes of nails. Why?  Just because -  These were changed by the scientist. He can pick up anything he likes!  Can he?!

15. Dependent variable:  Number of paper clips picked up (by what?) - magnet  The number of paper clips observed and counted (by whom? (measured) (by whom?)  What is your answer?

16. Controlled variables:  Battery, wire, type of nail  None of these items were changed  REMEMBER WHAT IS UNDER CONTROL?  WHAT ELSE IS NOT CHANGING?

17. Let’s go to one more example in Physical science!

18. The higher the temperature of water, the faster an egg will boil?! ARE YOU SURE ABOUT THAT? SHALL WE CHECK?

19.  WHAT WE HAVE IN THIS INVESTIGATION?  Let’s see:  Independent variable – temperature of water  Dependent variable – time to cook an egg  Controlled variable – type of egg

20. Last example for today in Physical Science: Remember the previous examples?! What did you get from those examples?! Any idea?!

21. The temperature of water was measured at different depths of a pond.

22.  LET’S SUMMARIZE OUR RESULTS:  Independent variable – depth of the water  Dependent variable – temperature  Controlled variable – thermometer

23. THIS IS A VERY IMPORTANT We are designing Investigations Basically we plan and do the steps of work to accomplish our final goal! Which was what?! Now do you see how all is connected and important?!

24. The greater the amount of soap in a soap and water mixture, the bigger a soap bubble can be blown.  Design an investigation to test this hypothesis.  Identify the variables  What exactly will be changed? How will it be changed?  What exactly will be measured? How will it be measured?  WRITE IT AS A HOMEWORK!

25. The farther a ball drops, the higher it will bounce.  Design an investigation to test this hypothesis.  Identify the variables  What exactly will be changed? How will it be changed?  What exactly will be measured? How will it be measured?  WRITE IT AS A HOMEWORK !