Units of Measurement

1. Meter m Liter L Celsius C Units of Measurement

2. Mass is the amount of matter, weight is a measure of the gravitational pull on matter

3. SI Units

4. PracticeIn each pair below, circle the larger

5. Basic SI Units

6. Metric Conversion king henryDied by drinking chocolate milk K h D base d c m 1.) 3.45 cm= Dm 0.00345 2.) 2.435 g= cg • 243.5 3.) 23.8 mL= L • 0.0238 4.) 14.8 km= m • 14800 5.) 23.5 cg= dg 2.35

7. Temperature Use both the Kelvin and Celsius scale, to convert Celsius + 273 = Kelvin Kelvin -273 = Celsius 293 20°C = K 100 373 K =°C

8. Volume: measured in cubic centimeters (cm3) or liters • 1 liter (L) = 1 cubic decimeter (dm3) = 1000 millileters (mL) • 1 mL= 1 cm3

9. Volume can be measure by Length xx or the Water Displacement method width height

10. Volume can be measure by Length x width x height or the Water Displacement method Know the relationship between the following volume units… L = mL = cm3(or cc in medical lingo) 1 1000 1000

11. Density • Is the ratio of mass per unit of volume. How much matter is packed into a given amount of space • Density = mass ÷ volume • D= M V

12. Constant • The Density of a substance stays regardless of the size of the sample. For example: if you cut a block of copper in half, you have decreased both the mass and volume, the ratio of the 2 stays the same. This is called an Intensive Physical Property.

13. g/cm3 • The appropriate units of density are: • for solids • for liquids g/mL

14. Example problems: • A sample of aluminum metal has a mass of 8.4g. The volume of the sample is 3.1 cm3. Calculate the Density of aluminum. D = 8.4 3.1 M= V =2.7 g/cm3 2 sig figs

15. Example problems: • Diamond has a density of 3.26 g/cm3. What is the mass of a diamond that has a volume of 0.350 cm3? D = 3.26 g/cm3 M = ? V = 0.350 cm3 D = M V 3.26g/cm3 x0.350 cm3 = 1.14 g 3 sig figs

16. Example problems: • What is the volume of a sample of liquid mercury that has a mass of 76.2 g, given that the density of mercury is 13.6 g/mL? V = ? M = 76.2 g D = 13.6 g/mL D= 76.2 g 13.3 g/mL = 5.7293 mL = 5.73 mL

17. Reliable Measurements • refers to the closeness of the measure value is to the , or real, value. • refers to how a series of measurements are to one another. Accuracy Actual Precision Close

18. Error accepted Experimental • is calculated by subtracting the value from the value.

19. The is the ratio of an error to an accepted value. percent error

20. % error = error x 100 = accepted value – experimental value x 100 accepted value accepted value

21. Example • An experiment finds the density of lead to be 10.95 g/cm3. The literature value for the density of lead is 13.34 g/cm3.

22. An experiment finds the density of lead to be 10.95 g/cm3. The literature value for the density of lead is 13.34 g/cm3. The error: accepted value – experimental value= • 13.34 – 10.95 = 2.39

23. The error: accepted value – experimental value= • 13.34 – 10.95 = 2.39 The % error: error x 100 % = accepted value 2.39 x 100 % = 13.34 17.9 %

24. Practice • Sara’s lab shows the atomic mass of aluminum to be 28.9. What is her percent error if the accepted value is 27.0? 28.9 – 27.0 = 1.90 1.90/27.0 x 100% = 7.04%

25. Practice • What is the percent error in a measurement of the boiling point of bromine if the textbook value is 60.8 °C and the lab value is 40.6 °C? 60.8 °C – 40.6 °C = 20.2 °C 20.2 °C / 60.8 °C x 100% = 33.2%