Units of Measurement SI units (Systeme Internationale d’Unites) were developed so that scientists could duplicate and communicate their work. Base UnitsDerived Units Lengthmeter (m)Volumemeter cubed (m 3 ) Masskilogram (kg)Density grams per cubic centimeter (g/cm 3 ) Time second (s) Temperature kelvin (K) A unit that is defined by a combination of a base units.

Density Ratio of an object’s mass to its volume What happens to density when mass is constant and volume changes?

Mass, Volume and Density Relationships Volume Mass Density Volume DIRECT INDIRECT

Temperature Scales

Reliability of Measurements Accuracyvs.Precision How close a measured value is to an accepted value How close a series of measurements are to one another High AccuracyLow Accuracy High Accuracy High Precision Low Accuracy High Precision

Percent Error Used to evaluate the accuracy of experimental data.

Pre-Class Activity What is the significance of this number? How would you express this number in scientific notation?

Scientific Notation 6.02 x Coefficient Exponent The coefficient must be greater than or equal to one and less than 10. When expressing numbers less than one (ex ) in scientific notation, the decimal point is moved to the right until the coefficient is within range. The number of spaces moved is used to determine the exponent. For numbers less than one, the exponent is negative When expressing numbers greater than 10 (ex. 1000) in scientific notation, the decimal point is moved to the left until the coefficient is within range. The number of spaces moved is used to determine the exponent. For numbers greater than 1, the exponent is positive.

Scientific Notation Calculations Multiplication and Division For multiplication, multiply the coefficients and add the exponents (1.3 x 10 4 ) x (2.0 x 10 6 ) = Remember, your final answer must be in the correct form. Often, multiplication of coefficients will yield a number greater than 10. In this case the result must be changed into the proper form. (5.3 x 10 4 ) x (2.0 x 10 6 ) = = For division, divide the coefficients and subtract the exponents. Often, division of coefficients will result in a value that is less than one. If this occurs, the final result must be changed into the proper form. (2.0 x )  (4.00 x 10 4 ) = = 2.6 x x x x x 10 -8

Scientific Notation Calculations Addition and Subtraction In order to add or subtract numbers in scientific notation, the exponents of each number has to be the same As a rule of thumb, it is best to take the number with the lower exponent and change it match the higher exponent. To increase an exponent, move the decimal point in the coefficient to left, the number of spaces equal to the increase in the exponent. Once the exponents are equal, the coefficients can be added or subtracted 2.1 x x x x x x x x x x 10 -4

Preclass Activity 10/20 How long is this paperclip? To what degree of certainty can it be measured?

Significant Figures in Measurement Scientists determine the precision of instruments by the number of digits they report.

Significant Figures in Measurement Measurements always include all certain digits and one uncertain digit mL

Measurement Challenge What value would you assign to each of these measurements? _________ mL _________ cm

Identifying Significant Figures in Numbers When examining a number, you determine the number of digits that are significant by the following rules: 1.All non-zero numbers are significant 2.All final zeros to the right of a decimal are significant 3.Zeros between significant digits are significant 4.For positive numbers less than one, all zeros directly after the decimal before the first significant figure are not significant. 5.All zeros at the end of a whole number are not significant.

Sig Fig Challenge How many sig figs are there in the following numbers:

Sig Fig Rules for Calculations Multiplication and Division Your answer can not contain more or less sig figs than the operator that contains the least number of sig figs x 0.45= Identify the significant figures, look on place beyond. If that digit is 5 or above, round up. If it is less than 5 drop off.

Sig Fig Rules for Calculations Addition and Subtraction Your answer can not be more precise than the least precise operator. Most of the time this means that your answer must have the same number of decimal places as the least precise operator cm +2.5 cm cm 14.9 cm 1060 cm cm cm 1080 cm If one of the numbers is a whole number that ends in zero(s), then the final answer must be rounded to the lowest place that contains a nonzero number.

Representing Data Graphing  Circle Graphs (based on percents)  Bar Graphs (How quantities vary)

Graphing continued Line Graphs In science, we draw a best fit line between data points. Do not connect the dots. Dependent Variable Independent Variable Which graph shows and indirect relationship between the dependent and independent variable?

Calculating the Slope of a Best Fit Line Select two points on the line that you have drawn. Do not select two of your data points because they might not fall on the line.