INTRODUCTION and MEASUREMENT Life Science: Biology – study of living organisms Physical Science: Chemistry – study of matter Physics – study of energy

Natural Law A description of phenomenon that is repeatedly and uniformly observed in nature. Observations. Also called a principle. Ex: an eclipse

Scientific Theory An explanation of why nature behaves the way described in the natural law. Comprised of well-tested and verified hypotheses.

Scientific Method The systematic approach to a question (6 steps) a. State a problem b. Collect background information andpast data c. Form a hypothesis d. Experiment e. Gather data and analyze results f. Draw a conclusion

Valid Experiment 2 requirements: One variable A control

Models A miniature representation or analogy used to help visualize something that cannot be easily visualized.

Units of Measurement International System of Units (SI units) metric units defined for scientific work. 2 advantages to the metric system: 1. portions of whole numbers are expressed as decimals. (eliminates repeating units) 2. easy conversion between different units because it is based on units of tens.

The Unit The arbitrary name given to a standard of quantity. Base units – 7 units that describe a single dimension –mass (kg)- length (m) –time (s)- temp (K) –quantity (mole) –electric current (A) –luminous intensity (cd)

Derived Units The combination of two or more base units. 9 common derived units: –area (m 2 )- volume (m 3 ) –force (N)- pressure (Pa) –energy (J)- power (W ) –voltage (V)- frequency (Hz) –electric charge (C) (see back cover of book for base units found in the above derived SI units)

Measurement (cont.) non-SI units liter (m 3 ) Celsius (vs. kelvin) Metric prefixes – (see p.12 table 1-3) 10 -9, 10 -6, 10 -3, 10 -2, 10 3 Writing large numbers in metric system spaces used in place of commas

Dimensional Analysis Conversion between units Unit equalities – equations to show how 2 units are related (1 m = 1000 mm) Conversion factors – equations using unit equalities that always equals one. ( 1m ) 1000 mm

Measurement (cont.) Scientific Notation A number expressed as a digit from 1-9 plus a power of ten. Uncertainty in Measurement: Precision – reproducibility of measurement by an instrument Accuracy – measured result compared to an accepted standard

Significant Figures All digits that are known to be true plus one uncertain digit. 5 Rules:a. all digits (1-9) are significant.b. zeros between non-zero digits are significantc. final zeros to the right of a decimal point are significant.

Significant Figures (cont.) d. Rules for numbers less than one (decimals) : Zeros to the left or right of the decimal points are not significant. Any zero after a digit (1-9) are significant. e. Any final zero in a whole number is not significant (according to this book)

Atlantic – Pacific Rule use a map of the United States. If a decimal is present, start with the first nonzero number on the Pacific side and count significant digits left to right. If a decimal is absent, start with the first nonzero number on the Atlantic side and count significant digits right to left.

Significant Digits (cont.) Addition & subtraction – the answer must have the same number of decimal places as the least accurate value used. Multiplication & division – the answer must have the same number of significant digits as the least accurate value used.

Percent Error % error = observed value – true value x 100 true value Compares the accuracy of a measurement to an accepted standard

Graphing x – axis: independent variable y – axis: dependent variable Required labels on each graph: –title of the graph –x-axis label –y-axis label Delta sign (  ) represents “change in” (final - initial).

Graphing (cont.) Equation of a line: y = mx + b Slope of the line: m =  y  x Line intercept: b value

Graphical Slopes indicate x and y relationships Positive slope: x increases as y increases Negative slope: x increases as y decreases Zero slope: y is not dependent on x nonlinear curves:y = x 2 (parabola) y = _1_ x(hyperbola)

Sample Problem 1 Which SI Unit would you use for the following measurements? –the length of a swimming pool –the mass of the water in the pool –the time it takes a swimmer to swim a lap

Sample Problem 2 Convert the following measurements as indicated: –6.20 mg in kg –3 x s in ms –88.0 km in m

Sample Problem 3 The following students measure the density of a piece of lead three times. The density of lead is actually g/cm 3. Considering all of the results, which person’s results were accurate? Which were precise? Were any both accurate and precise?

Sample Problem 3 (cont.) Rachel –11.32 g/cm 3, g/cm 3, g/cm 3 Daniel –11.43 g/cm 3, g/cm 3, g/cm 3 Leah –11.55 g/cm 3, g/cm 3, g/cm 3

Sample Problem 4 Perform these calculations, following the rules for significant figures. –26 x = ______ –15.3 / 1.1 = _____ – = ______ – = _______