2.  A quantity that contains both a unit and a number.  In chemistry you can make very large and very small measurements.  A single gram of hydrogen: 602,000,000,000,000,000,000,000 atoms  An atom of gold: 0.000000000000000000000327g Do you make measurements everyday?

3.  To make calculating easier you can write these numbers in scientific notation.  When a number is written as the product of two numbers.  A single gram of hydrogen: 6.02x10 23 atoms  An atom of gold: 3.27x10 -22

4.  84,000  0.00736  6,300,000  0.000008  94,700  0.00025

5.  5.32x10 -11  7.56x10 4  1.22x10 -9  4.33x10 10  8.1x10 -8  9.8x10 2

6. Accepted Value: the correct value based on reliable references Experimental Value: the value measured in the lab Error = Experimental Value – Accepted Value

7. Let’s Practice! A measurement of the boiling point of water was taken in a lab and found to be 99.1°C. The accepted value is 100°C. What is the percent error?

8. Why are significant figures significant?  Significant figures are important because they tell us how good the data we are using is. 200 grams 200. grams 200.00 grams  The first number has only one significant figure (the 2 in the beginning). Because this digit is in the hundreds place, this measurement is only accurate to the nearest 100 grams.  The second number has three significant figures. Because the last significant figure is in the ones place, the measurement is accurate to the nearest gram.  The third number has five significant figures. Because the last significant figure is in the hundredths place, the measurement can be considered to be accurate to the nearest 0.01 grams.

9. There are 5 main rules for significant figures. Rule # 1: Every NON-ZERO digit in a measurement is assumed to be significant!

10. Rule #2: Zeros that appear between NON-ZERO digits are significant. 7003 40.79 1.503

11. Rule #3: Zeros that appear to the left of NON-ZERO digits/the beginning of a number are NOT significant. **They act as placeholders** 0.0071 0.42 0.00099

12. Rule #4: Zeros at the end of a number and to the right of a decimal point are ALWAYS significant. 43.00 1.010 9.000

13. Rule #5: Zeros that are to the right of a number and to the left of a decimal point are NOT significant. 300 7000 27,210

14.  Results from the specificity of the measuring device.  Estimating the last digit in a measurement. How are beakers different from graduated cylinders? Which is more specific?

17. 30.0°C

18. 5.72 mL 3.0 mL0.35 mL

19. A sample of liquid has a measured volume of 23.01 mL. 1. How many significant figures does this measurement have?

20.  300.0  650  412.07  1320  102.0005

22.  When adding/subtracting, the answer should be rounded to the same number of decimal places as the number with the least number of decimal places. 234.56 + 123 + 43.0 = ? 401

23.  When multiplying/dividing, the answer should be rounded to the same number of decimal places as the number with the least number of decimal places. 7.55m x 0.34m = ? 2.6m 2

24.  This is a revised version of the metric system.  6 commonly used SI base units:  Length - Meter (m)  Mass - Kilogram (kg)  Temperature - Kelvin(K)  Time - Seconds (s)  Amount of Substance - Mole (m)  Energy – Joule (J)

25. PrefixFactor Mega (M)10 6 Kilo (k)10 3 Deci (d)10 -1 Centi (c)10 -2 Milli (m)10 -3 Micro (µ)10 -6 Nano (n)10 -9 Pico (p)10 -12

26.  How do the metric prefixes relate to the SI base unit?  Measurements are not always taken in the base unit and need to be converted using the metric relationships.

27.  Mass:1 kg = 1x10 3 grams  Length: 1 m = 1x10 -3 km  Volume: 1 L = 1x10 3 mL  Energy: 1 J = 1x10 -3 kJ

28.  Kelvin and Celsius are the two equivalent units of temperature.  Celsius sets the freezing point of water at 0 ˚C.  Kelvin sets the freezing point of water at 273.15 K. K = ˚C + 273.15 ˚C = K – 273.15