1. CHAPTER 3. Density and measuring technique CHEMISTRY 1105

2. Metals ► 90% of the elements on the Periodic Table are metals ► Physical properties define the metal ◦Weight ◦Mass ◦How about volume? ◦How about the phase of the metal? ► Melting Point ► Boiling Point

3. Where are the metals in the P.T?

4. We will determine the density of a metal!

5. Density ◦A physical property ◦How heavy something is compared to its size. ◦Relationship between mass and volume

6. But why? ◦Type of Molecules ◦Crystal structure ◦Interactions

7. Remember

8. Density of liquids If two liquids of different densities are poured together, they form tow layers: Top  Liquid with lowest density Bottom  Liquid with highest density

9. Experiment

10. Materials ? 50 & 100 mL 10 mL

11. Density of a solid How will we do it? Measuring the displacement of H 2 0 2 1 Weigh the metal

12. Procedure 1.Select you metal and record how it looks like. 2.Using the balance, get 3 different mass measurements of the metal ◦Small  medium  large (1 time each) ◦Then repeat two more times! ◦Total= 9 measurements ◦Do it for precision

13. To determine the volume We know that an object will displace its own volume within another volume 3.Use a 10 mL graduated cylinder 4.Fill it with 5 mL of DI H 2 0, and get rid of bubbles. Record the exact initial volume (meniscus). 5.Place metal pieces into graduated cylinder (angle). 6.Get rid of bubbles and record the final volume.

14. Repeat for each of the metal sizes Do it 3 times!

15. Computer calculations The change in volume equals the volume displacement Volume of metal = Final volume – Initial volume 1.Login the computer 2.Open Excel 3.Blank workbook

16. Spreadsh eet 4.Fill the column names ◦Column A: Size ◦Column B: Trial ◦Column C: Mass ◦Column D: Initial volume ◦Column E: Final volume ◦Column F: Displaced volume 5.Fill the first row information ◦1 to 3: Small ◦4 to 6: Medium ◦7 to 9: Large 6.Fill the second row information ◦1, 2, 3 (three times)

17. 7.Fill in the data from your experiment 8.Calculate the volume displaced by your metal. ◦Use an excel formula ◦Pull the box all the way down to copy the formula Analysis & Graph

18. 9.Hide columns D and E Analysis & Graph

20. 10.Select mass and volume values 11.Insert graph ◦Scatter 12.Fill the graph with your information: X axis: Volume (mL) Y axis: Mass (g) Title: Density of (describe) metal Analysis & Graph

21. 13. Select one of the dots ◦Right click ◦Add trendline ◦Linear ◦Display equation on chart Analysis & Graph

23. y = m*x + b m –slope which relates accuracy b –intercept which is the density

24. Find the unknown! ◦Chemistry book ◦Periodic table ◦Write it in your report

25. Print one copy of the Excel sheet per group member

26. Density of a liquid How will we do it? Measuring the mass of the liquid and the volume it occupies 21 Weigh the liquid Record the volume of liquid

27. Procedure 1.Use a 100 mL beaker and get 50 mL of the unknown liquid 2.Rinse the pipette with 5 mL of liquid and discard it 3.Clean and dry a 50 mL beaker and weight it empty. Record this mass waste

28. 4.Pipette 3 to 6 mL of liquid ◦Record the exact volume 5.Pour the liquid in the beaker and record the mass (do not subtract the mass of the beaker) Repeat the process 8 more times, but leaving the previous liquid in the beaker

29. Calculations Repeat the same procedure in Excel Open a second sheet

30. y = m*x + b b –the weight of the beaker m –slope which is the density

31. Find the unknown! ◦Chemistry book ◦Write it in your report

32. Print one copy of each sheet per group member

33. Report ◦Print graph and table ◦Staple graph and report together ◦Don’t forget to describe and name your unknown! ◦Staple all lab reports together ◦Clean everything before leaving and place it back in its place.