Name: _______________________________________ Variables – Lab Review Answer the following questions based on yesterday’s lab and your understanding about variables. You should use your notebooks with your notes and lab notes to aid you. 1. What was the Independent Variable being investigated? IV: Temperature (evidenced by hot water, heating test tubes) 2. What was the Dependent Variable being solved? DV: Reaction rate/speed (evidences by “racing” and mixing same time) 3. Identify as many controlled variables as you can from this experiment: 10 drops chem A in both A test tubes 10 drops chem B in both B test tubes 1 set test tubes (A&B) put into hot water same time 1 set test tubes (A&B) placed in test tube rack/room temp Mixed both sets chemicals at same time 4. This experiment is known as a Controlled Experiment. Why is it considered this? Two sets of identical chemicals mixed with same results at same time but only one change made; IV 5. How was the independent variable tested? Explain. One set of test tubes put into hot water to warm temp; other set of test tubes left at room temp; both sets mixed same time and results compared by looking for which set reacted first. 6. There were two sets of chemicals tested. Write the formulas for the two sets (be careful, not two chemicals, two sets): KMnO4 And KI K2S2O8 And H2C2O4 Page 1 of 4 Name: _______________________________________ 7. How did the two different set of chemicals differ? List any observable differences before and after the test. Before – one set both liquid, one colorless, one purple; second set both liquid, both colorless After – both sets turned yellow liquid The following questions are about only the one set of chemicals your group tested: 8. You did two tests. Which test was the “normal” experiment? The chemicals at room temp 9. Why is this set considered the “normal” experiment? No changes were made to vary experiment 10.How did you make sure that there were no other factors that would influence this test? Exact measurements of drops, size and number were placed in each test tube; chemicals were mixed at same time by stating “ready, set, go” with partner; same type droppers/pipets were used 11. What factors could have changed your final results if your group wasn’t careful (error – human error is not an answer)? Too big or small of drops; miss counting drops; water left in test tube; not mixing exactly at same time; holding “normal” set causing them to warm up, etc. 12. How did you know when the experiment was “finished” or reacted? Known color change of yellow was achieved 13. You completed two tests with same chemicals. Did both sets of chemicals react the same way? Yes, because it was the exact same chemical with only a temp change Page 2 of 4 Name: _______________________________________ 14. Why is this important (number #13)? In conducting an experiment, only one variable can be tested at a time which was temp 15. How did the second test differ from the first test? For the second set of chemicals we changed only the temp of the chemicals, everything else was the same 16. What parts of the second test remained the same as the first test? Number of drops of each chemical, time waited to mix, mixing at same time, etc. 17. Why is this important (number #16)? When conducting controlled experiment only one factor can be tested at a time or the results will change/be flawed 18.How did you know if the “changed” variable affected the reaction of the chemicals? By comparing the results of the “normal” set or controlled set of chemicals 19.In the end, the results of this experiment was (evidence of change)… The observation of yellow color change, which occurred in the hot chemicals first, shows that heating the chemicals speeds up the reaction 20. In making the statement in #19, could you say this statement is the same for the other set of chemicals the other group tested? (more than a yes/no answer- explain) For the chemical test by the other group, their results showed also that heating the chemicals speeds up the reaction 21. Make an inference regarding your final results using the data collected from both your group’s experiment and the other groups’ experiments. Heating up chemicals will cause them to react faster when mixed together Page 3 of 4 Name: _______________________________________ 22. Write a Theory for this experiment (look the definition up if you are unsure). (Theory is explaining why something happens) When heating chemicals, this causes the chemicals to react faster because the particles that make them up collide faster (work) 23. Write a Law for this experiment (look the definition up if you are unsure). (Law description of how something happens) When heating any substances/chemical before mixing them, will cause their reactions to occur faster 24. What is the difference in these two statements. A Theory is an explanation of why something happens where a Law describes what is happening Page 4 of 4