1. CHEM 10171-04 Dr. Nicole Brinkmann [email_address] 415 Jordan Hall of Science 1-1302

3. Why study chemistry?

4. Pose an explanation Try Something Observation Ask Questions Pose an Explanation Combustible materials contain phlogiston Some more (charcoal), some less (metal) Burn charcoal in closed container Fire goes out Why does phlogiston need air? Air gets saturated with phlogiston Some things burn more than others Observation Why? Ask Questions Burn metal Try Something Forms calx which weighs more than metal Observation How can the loss of phlogiston increase the mass? Ask Questions Phlogiston has negative mass Pose an Explanation

5. Observation Ask questions Pose an explanation Try something If new observation Ask more questions Pose additional explanations

6. Heated Hg calx and got Hg and gas Total mass of Hg & gas = mass Hg calx Heated Hg with gas and got Hg calx Mass Hg calx = total mass of Hg & gass Observation Why? Ask Questions Heating Hg with gas caused the two to combine into the calx; heating the calx caused it to break into Hg and the gas Pose an explanation Burn Hg in closed container then light candle in container Try Something Candle goes out Observation Ask Questions Is this consistent with previous observations & explanations? Yes Propose a theory No Revise

7. Observation (Ask questions) Hypothesis Experiment Observation Ask more questions Propose a theory Revise hypothesis as needed Further experiments Revise theory as needed MODERN SCIENTIFIC METHOD

9. Properties & Changes If you combine A&B and get C, is this a chemical change or physical change? Chemical change because the Substances have changed composition.

10. Properties & Changes If you combine A&B and get D, is this a chemical change or physical change? Chemical change because the Substances have changed composition.

11. Properties & Changes If you change the conditions C and get D, is this a chemical change or physical change? Physical change because the Substances have changed composition.

12. Properties & Changes If you change the conditions C and get D, does D have different properties than C? Same chemical properties b/c it’s the same substance. Different physical properties b/c it’s in a different form.

13. Properties & Changes Are there chemical or physical changes between A and B? CC: 3Y 2 + 3R -> RY 2 (new composition) CC: 3R + 3B -> 3RB (new composition) PC: 3B(s) -> 3B(g)

16. Energy (b) Two states of the same system are shown as (a) and (b). Where does each state belong in the PE diagram? Where does the PE go when it is lost from the state with higher PE?

17. Energy

18. Measuring What is the length of the metal strip? (a) 7.5 cm (b) 7.25 cm (c) 7.4 cm (d) 7.45 cm In science, we use significant figures – all the digits you can read plus the first digit that you can estimate.

19. Density D W = 1.0 g/mL, D C = 0.88 g/mL, D A = 1.4 g/mL Which is a possible density for B? (a) 0.79 g/mL (b) 0.86 g/mL (c) 0.94 g/mL (d)1.2 g/mL

20. Density = M/V units: g/mL D W = 1.0 g/mL, D C = 0.88 g/mL, D A = 1.4 g/mL Which is a possible density for B? (a) 0.79 g/mL (b) 0.86 g/mL (c) 0.94 g/mL (d)1.2 g/mL D C < D B D B < D W D W < D A

21. You have 3 pieces of metal each having the same mass. You drop each into one of three graduated cylinders each of which started with 25.0 mL of water. Which metal is the most dense? V = 3.2 mL V = 2.9 mL V = 3.5 mL D = M/V division by the smallest V will give the biggest D

22. If the mass of B is 25.0 g, what is the density of B? (a) 8.6 g/mL (b) 8.62 g/mL (c) 8.621 g/mL (d) 8.6207 g/mL

23. A 25.0 g sample of water was measured four times by four different students. Which student(s) was(were)precise in his/her measurements? Which was (were) accurate? A B D C