Measurement & Sig Figs!

1. Measurement &Sig Figs!

2. MASS Mass: The amount of matter in an object. What do we use to measure mass? Electronic balance UNITS: grams

3. VOLUME Volume: The amount of space occupied by an object

4. VOLUME OF A LIQUID: UNITS: mL What is this curved line called? Meniscus Do you measure the amount of liquid at the highest part of the meniscus or the lowest part? LOWEST (Bottom) How much water is in this graduated cylinder to the correct number of DECIMALS? 43.0

5. VOLUME OF A REGULAR SOLID UNITS: cm3 Length x Height x Width

6. VOLUME OF AN IRREGULAR OBJECT UNITS: mL 2 2 2.40 mL - 1.65 mL = 0.75 mL + 1 1

7. DENSITY OF AN OBJECT UNITS: g/mL OR g/cm3 Density:The amount of mass per unit volume (AKA how closely the particles are packed). I zoomed in on the particles of 2 blocks of metals. Which metal would have a higher density? Metal A Metal B

8. m I DENSITY V mass divided by volume

9. m v D

10. What is the density of an object that has a mass of 2.00 grams and a volume of 1.0 mL? m v D

11. What is the volume of an object that has a mass of 8.00 grams and a density of 2 g/mL? m v D

12. What is the mass of an object that has a density of 3.0 grams/mLand a volume of 10.0 mL? m v D http://www.explorelearning.com/index.cfm?method=cResource.dspView&ResourceID=362

13. 0008008399990432879.00000004000000 Which digits are significant?

14. Measurement ** Always read as many places as possible from the instrument and then estimate one additional place. • The last number that you record is the one • you are uncertain about Practice: Which digit is uncertain? 43.29 23 184.2 43.29 23 184.2

15. Example: An instrument reads to the nearest tenth. You should estimate to the nearest _________________. hundredth Example: A scientist records a measurement as 23.4 mL. The instrument must have ______________ increments. 1 mL

16. How long is the yellow cylinder? 1.25cm (but you could say any # for the 5 and still be correct! The 5 is the estimated digit since the instrument measures to the tenths place)

17. Estimate one spot past the line you can see • If markings are given every 10 ml… • Estimate to the 1’s place (ex: 15 ml) • If markings are given every 1 ml… Estimate to the tenths place (ex: 15.0) • If markings are given every 0.1 ml… • Estimate to the hundreths place (ex: 15.00)

18. The odd cases • If markings are given for 0.2 ml… • Still estimate to the 100th place (ex: 15.00) • If markings are given every 25 or 50 ml… • Don’t use as a measuring device!! • If you DO use it to measure, measurements should be something like “90ml”, not “90.0 ml”

19. Density LAB!! • If your “beginning volume of water” is always exactly 50.0 ml, this tells me you are either… • Making stuff up =) • Spending way too much time fiddling with your water levels • When measuring: Place the graduated cylinder on a flat surface, get down to eye level, and think about significant figures!

20. Working as a group… • Each table of 4 people will have 1 bag that contains 7 pieces of metal (erase row #8 on your data table) • Each person should makes at least one volume and one mass measurement. • Use your materials wisely: one person can use the graduated cylinder while the other weighs, and then switch! • Discuss significant figures as a group. If you can’t agree on how many you should record- please ask me for help!

21. Showing work! • See rubric: include units in both your work and your answers! • You will ALWAYS do this in labs and on tests in this class!