Measurement and the Metric System

1. Measurement and the Metric System Experiment 2

2. Measurement • All measurements in the chemistry lab will be taken using metric units. • Always read a measuring device to the maximum number of digits possible. • Uncertainty – last digit of a measurement is estimated. • Always include the units with a measurement.

3. Metric Units

4. Metric Prefixes

5. Measuring Temperature • Will measure temperature in units of Celsius or Centigrade oC • Will use units of Celsius or Kelvin for temperature • To convert Celsius to Kelvin add 273.16 K • 35.5 oC + 273.2 K = 308.7 K • 533.4 K – 273.2 K = 260.2 oC

6. This thermometer should be read to the nearest 0.1 oC

7. This thermometer should be read to the nearest 0.01 oC

8. Measuring Mass • Mass will generally be measured in units of grams(g), or kilograms (kg). • If using an electronic balance, always record all digits showing on the balance.

9. This electronic balance should be read to the nearest 0.001 g.

10. Quad Beam Balance This quad beam balance should be read to the nearest 0.001 g.

11. This is a balance like we use at Grossmont. Note that the scale is calibrated to the nearest 0.01 g so you should be able to read it to the nearest 0.001 g.

12. Measuring Volume • Volume will be measured in liters (L) or milliliters (mL). • Sometimes measured in cm3. 1 cm3 = 1 mL • When measuring volumes in a graduated cylinder always measure the volume at the bottom of the meniscus.

13. This graduated cylinder should be read to the nearest 1 mL.

14. This graduated cylinder should be read to the nearest 0.1 mL. This graduated cylinder contains 27.4 or 27.5 mL of liquid.

15. This graduated cylinder should be read to the nearest 0.01 mL.

16. No writeovers 375.788g No obliterations 639.824g No Erasing Cross out once and rewrite. 4.932g 5.382g Be sure to write all data in your lab book in black or blue ink when you take the data. Any data recorded on stray pieces of paper will be confiscated! Rules for recording data 636

17. Today’s Experiment • Part 1 – Measuring temperature and mass • Measure temperature of room temperature water, boiling water, ice water, and salted ice • Use the quad beam balances to measure mass of beaker and salt. • When measuring out salt, do not try to get exactly 6 g of salt. Anything between 5.5 and 6.5 grams is fine

18. Use of Bunsen Burner Not enough oxygen Better

19. Today’s Experiment • Part 2 – Volume measurements • Remember to read measurements at bottom of meniscus • Read 50 or 100 mL graduated cylinder to nearest 0.1 mL • Read 10 mL graduated cylinder to nearest 0.01 mL.

20. Today’s Experiment • Part 3 – Calibrating your eye-dropper • Add drops to the 10 mL graduated cylinder to increase the volume by 1 mL. • Determine the number of drops of water in 1 mL. • Calculate the volume of one drop of water.

21. Today’s Experiment • When you have finished gathering data you need to answer the questions at the end of the lab report. • After completing the lab report complete worksheet #1 • If you finish both of these before the end of the period, turn them in. Otherwise they are due next week in lab.

22. What is due today? • Experiment 1 from last week. • Worksheet #1 and Experiment 2 from this week if you plan to leave more than 15 minutes before the end of class.