2. Units of Measurement  Scientists use the International System of Units, or SI system  This allows easier sharing of data and results

3. Units of Measurement  SI Base Units QUANTITYUNITABBREVIATION Lengthmeterm Massgramg Timeseconds TemperaturekelvinK Electric currentampereA Amount of substancemolemol Luminous intensitycandelacd

4. Units of Measurement DDerived units (combinations of base units) are used for measurements like area, volume, pressure, weight, force, speed, etc. TThe SI system uses prefixes to express very small or very large numbers. TThese prefixes are all multiples of 10.

5. Prefixes Used for Large Measurements PREFIXSYMBOLMULTIPLE OF BASE UNIT SCIENTIFIC NOTATION tetra-T1 000 000 000 00010 12 giga-G1 000 000 00010 9 mega-M1 000 00010 6 kilo-k100010 3 hecta-h10010 2 deka-dk1010 1

6. Prefixes Used for Small Measurements PREFIXSYMBOLMULTIPLE OF BASE UNIT SCIENTFIC NOTATION deci-d0.110 -1 centi-c0.0110 -2 milli-m0.00110 -3 micro-µ0.000 00110 -6 nano-n0.000 000 00110 -9 pico-p0.000 000 000 00110 -12

7. Units of Measurement  If you are converting to a smaller unit, multiply the measurement to get a bigger number.  Example: Write 1.85 m as centimeters.

8. Units of Measurement  If you are converting to a larger unit, divide the measurement to get a smaller number.  Example: Write 185 cm as meters.

9. Units of Measurement: Practice 1. Write 550 millimeters as meters. 2. Write 3.5 seconds as milliseconds. 3. Convert 1.6 kilograms to grams. 4. Convert 2500 milligrams to kilograms. 5. Convert 4 centimeters to micrometers. 6. Change 2800 millimoles to moles. 7. Change 6.1 amperes to milliamperes. 8. Write 3 micrograms as nanograms.

10. Units of Measurement  Most often, you will measure things like time, length, mass, and volume.  Length = a measure of the straight-line distance between two points  Mass = a measure of the amount of matter in an object  Volume = a measure of the size of a body or region in three-dimensional space

11. Units of Measurement  Weight and mass are not the same thing.  Weight = a measure of the gravitational force exerted on an object

12. Writing Numbers in Scientific Notation  Scientists sometimes need to express measurements using numbers that are very large or very small.  To reduce the number of zeros, values can be expressed as a simple number multiplied by a power of 10.  This is called scientific notation.

13. Writing Numbers in Scientific Notation Power of 10Decimal Equivalent 10 4 10 000 10 3 1000 10 2 100 10 1 10 10 0 1 10 -1 0.1 10 -2 0.01 10 -3 0.001

14. Writing Numbers in Scientific Notation: Practice  Write the following measurements in scientific notation: 1. 800 000 000 m 2. 0.0015 kg 3. 60 200 L 4. 0.000 95 m 5. 8 002 000 km 6. 0.000 000 000 06 kg

15. Writing Numbers in Scientific Notation: Practice  Write the following measurements in long form: 1. 4.5 x 10 3 g 2. 6.05 x 10 -3 m 3. 3.115 x 10 6 km 4. 1.99 x 10 -8 cm

16. Using Scientific Notation  When using scientific notation in calculations, you follow the math rules for powers of 10.  When you multiply two values, add the powers of 10.  When you divide two values, subtract the powers of 10.

17. Using Scientific Notation  Perform the following calculations: 1. (5.5 x 10 4 cm) x (1.4 x 10 4 cm) 2. (2.77 x 10 -5 m) x (3.29 x 10 -4 m) 3. (4.34 g/mL) x (8.22 x 10 6 mL) 4. (3.8 x 10 -2 cm) x (4.4 x 10 -2 cm) x (7.5 x 10 -2 cm) 5. (3.0 x 10 4 L) / 62 s 6. (6.05 x 10 7 g) / (8.8 x 10 6 cm 3 ) 7. (5.2 x 10 8 cm 3 ) / (9.5 x 10 2 cm) 8. (3.8 x 10 -5 kg) / (4.6 x 10 -5 kg/cm 3 )

18. Using Significant Figures  Precision = the exactness of a measurement  To show the precision of a measured quantity, scientists use significant figures.  Significant figure = a prescribed decimal place that determines the amount of rounding off to be done based on the precision of the measurement

19. Using Significant Figures  Accuracy = a description of how close a measurement is to the true value of the quantity measured  A measured quantity is only as accurate as the tool used to make the measurement.  When you use the measurements in calculations, the answer is only as precise as the least precise measurement used in the calculation – the measurement with the fewest significant figures.

20. Using Significant Figures: Practice  Perform the following calculations, and write the answer with correct number of significant figures. 1. 12.65 m x 42.1 m 2. 3.02 cm x 6.3 cm x 8.225 cm 3. 3.7 g / 1.083 cm 3 4. 3.244 m / 1.4 s

21. Rules for Determining the Number of Significant Figures 1) All nonzero digits are significant. Example: 1246 2) Any zeros between significant digits are also significant. Example: 1206 3) If the value does not contain a decimal point, any zeros to the right a nonzero digit are not significant. Example: 1200

22. Rules for Determining the Number of Significant Figures 4) Any zeros to the right of a significant digit and to the left of a decimal place are significant. Example: 1200. 5) If a value has no significant digits to the left of a decimal point, any zeros to the right of the point, and to the left of a significant digit, are not significant. Example: 0.0012

23. Rules for Determining the Number of Significant Figures 6) If a measurement is reported that ends with zeros to the right of a decimal point, those zeros are significant. Example: 0.1200

25. Presenting Scientific Data  Line graphs are best for displaying data that can change.  The x-axis usually shows the independent variable.  The y-axis usually shows the dependent variable.

26. Presenting Scientific Data  Bar graphs are best for comparing similar data for several individual items or events.  These graphs often clearly show how large or small the differences in individual values are.  Pie charts are best for displaying data that are parts of a whole.

27. Line Graphs  Line graphs show the relationship between an independent and a dependent variable very clearly.  The independent variable is plotted on the x-axis.  The dependent variable is plotted on the y-axis.  You have to be sure to properly label both axes and include the units for the values.

28. Line Graphs

29. Scatter Plots  A scatter plot is very similar to a line graph.  The data points are plotted on the graph using the x- and y-axes.  They are often used to find trends in data by using a best-fit line.  This line represents all of the data points without necessarily going through all of them.  To find a best-fit line, pick a line that is equidistant from as many data points as possible.  This line can show a trend more clearly and points on the line can be used to determine its slope.

30. Scatter Plots Jacket Sales Temperature (°C) Number of Jackets Sold 1100 1001 903 805 7025 6049 5087 40104 30276

31. Bar Graphs  Bar graphs are used to compare data quickly and to identify trends.  The data represented by these graphs are represented accurately, but it isn’t easy to draw conclusions quickly.

32. Bar Graphs

33. Pie Charts  Pie charts provide an easy way to visualize how parts make up a whole.  They are typically made from percentage data.  To make a pie chart, we can estimate the portions of the circle that each percentage would require.  We can also use protractors, which is helpful when the data can’t be converted into simple fractions.

34. Pie Charts Student Grades Letter GradeNumber of Students A4 B12 C10 D2