2The Nature of Science Scientists try to answer questions about the natural world by:Exploring the unknownExplaining the knownExperimenting to test theories or confirmfacts
33 Main Branches of Science Biological- Botany, Ecology, Zoology, etc.Physical- Physics (motion), Chemistry (matter)Earth- Geology, Astronomy, Meteorology
4The Way Science Works: Scientific Method Used to learn about the natural world; includes thefollowing steps:Making observationsAsking questionsForming a hypothesis; making a predictionTesting the hypothesis through experimentationCollecting and analyzing data from experimentDrawing conclusion(s) from dataCommunicating data to peers or public
5Scientific Method (cont’d) Only 1 question investigated at a time.Controlled experiments- compare experimental group (variable) to control group (lacks variable).*independent variable= variable/factor tested*dependent variable= variable measured quantitatively (numbers)Experiments can only disprove an hypothesis.
6Scientific ThinkingInference= conclusion drawn from previous data, not on direct observation.Theory= explains why something happens.Law= describes how something works.
7Units of Measurement- System International (SI) Units QuantityBase UnitAbbreviationLengthmetermMasskilogramkgTimesecondsTemperatureKelvinKAmountmolemol
8Metric System (based on 10) based on powers of 10 PrefixSymbolMeaningMultiply base unit by...giga-Gbillion1,000,000,000mega-Mmillion1,000,000kilo-kthousand1000BASEUNITdeci-dtenth0.1centi-chundredth0.01milli-mthousandth0.001pico-umillionth(5 zeros!)nano-nbillionth(8 zeros!)BIGGERSMALLER
9Metric Conversions (Only SI units are used to express scientific data) To convert from 1 unit to another:1. Identify given unit; unknown unit.2. Use dimensional analysis to compareknown to unknown unit (factor-labelmethod) Ex. How many pounds are in 1000 grams?
11An object’s mass is 250 kg. What is its mass in grams?
12Organizing Data: Graphs Line Graph: for continuous dataBar Graph: compare similar data for several thingsPie Graph: compare parts of a wholeFavorite StoresCar SpeedOur Ages
13Graphing Data Independent Variable: changed by scientist; x-axis Dependent Variable: “depends” on independent variable; y-axisDistance (m)Time
14How to Make a Line Graph Label x-axis with dependent variable Label y-axis with independent variableChoose increments to represent data on each axis.Plot points.Connect points.Name graph.Distance (m)Time (s)
16Scientific Notation Reduces # of 0’s in very large or small numbers. Expresses simple #’s x power of 10.(simple #- 1 < number < 10)
17Writing Scientific Notation 1. Identify first number between 1 and Place decimal after that number. 3. Count number of places the decimal had to move- this is the exponent of 10. ex. 210,000,000,000,000,000,000,000 m 2.10,000,000,000,000,000,000,000 m (decimal was moved 23 places to the left) sci notation= 2.1 x 1023
18Writing Scientific Notation (cont’d) If decimal moves to right, exponent is negative (original number is less than 1)If decimal moves to left, exponent is positive(original number is 1 or greater)ex cm0x cm(decimal was moved 8 places to the right)sci notation = x 10-8 cm
19Write 28750.9 in scientific notation. x 10-5x 10-4x 104x 105
20Write 2.87509 x 104 in standard notation 287,509.
21Calculating Scientific Notation (Follow math rules for powers of 10)*multiplication= add powers of 10**division= subtract powers of 10ex x x 1027.2 x x 102sci notation = 6 x
22Significant Figures Number of meaningful digits in a quantity. Significant figures are:1. Any # that is not a zero.ex (4 SF)2. Zeros between nonzeros.ex (4 SF)3. Zeros to right of decimalex (4 SF)
23Significant Figures (cont’d) Significant figures are not:1. Zeroes after nonzeros unless a decimal ispresent.ex. 80,000 (1 SF)ex. 83,000 (2 SN)ex (5 SN)ex (5 SN)
24Putting It All Together: Chewing Gum I’ve noticed that when I chew gum, the size changes.How does the amount of time gum is chewed affect the mass?Looking through the literature on gum, I see that others have noticed what I’ve noticed, but no one has done an experiment on this.
25My hypothesis: I think the gum will get smaller as it gets chewed because the sugar will dissolve. I create an experiment where I time chewing gum and weighing it at different intervals.I perform the experiment and collect dataYOU will do this in the lab!