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## Introduction to Science

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**Introduction to Science**Science = the study of the world around us. Knowledge of the physical or material world gained through observation and experimentation.**The Nature of Science**• Scientific law versus theory: • Scientific law: a summary of an observed natural event. • Scientific theory: a well tested, possible explanation of a natural event.**The Way Science Works…**• Science involves critical thinking, or applying logic and reason to observations and conclusions. • Observation vs. Inference • Observation: descriptive of what you see, hear, taste, feel, smell • Inference: an assumption made as a result of an observation (not always correct!!)**Variables and Controls**• A variable is anything that can change in an experiment. • Independent variable: The variable being changed or controlled by the scientist. • Dependent variable: The variable being measured or observed by the scientist. • A controlled experiment tests only one variable at a time.**The Scientific Method:A series of logical steps to follow in**order to solve problems. • OBSERVE • FORMULATE A QUESTION • FORM A HYPOTHESIS • DESIGN AND CONDUCT AN EXPERIMENT • MAKE OBSERVATIONS • RECORD AND ANALYZE DATA • DRAW CONCLUSIONS • FORMULATE NEW QUESTIONS and CONTINUE CYCLE**Making Measurements**• Measurements are made in this class using SI units. • LENGTH (m): distance between 2 points • VOLUME (L): space occupied. • MASS (kg): the amount of matter in an object. • WEIGHT (N): the force with which gravity pulls on a quantity of matter.**Precision vs. Accuracy**• Accuracy: the extent to which a measurement approaches the true value. • Precision: the degree of exactness of a measurement. • A scale may be precise to the nearest 100th of a gram, or +/-0.01g**Precision vs. Accuracy**increasing precision increasing accuracy**Density = mass/volume**• Example 1: • What is the density of water if a 5 mL sample of water has a mass of 5 g? M D V**Example 2**• What is the mass of 10 mL of a liquid that has a density of 3.76 g/mL? d = m / v m = dv m = (3.76 g/mL)(10 mL) m = 37.6 g**Coke vs. Diet Coke**• Which is less dense? Meaning which will float in water? • Coke or Diet Coke?**Calculations**• Calculate the density of each: • A can of Coke has a volume of 355 mL and a mass of 394 g (assuming that the weight of the aluminum can is constant) • A can of Diet Coke has a volume of 355 mL and a mass of 355.1 g (assuming that the weight of the aluminum can is constant)**WHY is Diet Coke less dense?**• There is less mass in the same volume (355 mL) • Coke has 39 grams of sugar in it to sweeten it (355 + 39 = 394 g) • Diet Coke only needs 0.1 g of Nutra Sweet to make is just as sweet as Coke (355 + 0.1 = 355.2 g)**Temperature Conversions**• Temperature is a measure of the average kinetic energy in a system. • K = Kelvin • oF = degree Fahrenheit • oC = degree Celsius**Temperature Conversions**• K = oC + 273 • oF = (1.8 x oC) + 32 • oC = (oF – 32) / 1.8**Percentage Error**• Calculate this value in labs where the accepted value is given.**Organizing DataData is organized and presented in tables,**charts, and graphs. GRAPHING... Graph - visual representation of data 1) title 2) x and y axis labeled 3) units for both the x and y axis 4) scale is evenly and correctly spaced for data 5) legend when appropriate**LINE**GRAPH LINE GRAPH: best for displaying data that change. • Independent Variable: x-axis • Dependent variable: y-axis**BAR GRAPHS**BAR GRAPH: useful when you want to compare data for several individual items**PIE CHARTS**PIE CHART: ideal for displaying data that are parts of a whole.**Scientific Notation/Powers of 10**Significant Figures Dimensional Analysis (Factor Label Method)**MATH IS THE**LANGUAGE OF CHEMISTRY!!!**Scientific Notation**Scientist use special notation to expressvery largeorvery smallnumbers. Example I: 300,000,000 m/sec can be written as… 3 x 108 m/sec Ex II: 1,007,000,000 sec can be written as… 1.007 x 109 sec Ex III: 0.000 000 000 004 76 m can be written as… 4.76 x 10-12 m**Converting Metric Measurements(PART 4 of Things to Know and**Love) To convert, move the decimal place the number of stairs you step on in the direction you are traveling OR use dimensional analysis. kilo- 103 hecto- 102 deca- basic unit 101 1 deci- Example: 3.75 km = ? mm 10-1 centi- 10-2 milli- ? = 3,750,000 mm 10-3**Video**• Powers of Ten**SIGNIFICANT FIGURES**• Scientists indicate the precision of measurements by the number of digits they report = sig. figs. • A value of 3.52 g is more precise than a value of 3.5 g • All known digits plus one estimated digit ** the equipment used for a measurement will determine the number of sig. figs.**Significant Figures**Atlantic - Pacific Rule: Decimal Present: Count from the Pacific side Decimal Absent: Count from the Atlantic side Start counting at the first non-zero number and count until you reach the end of the number Ex. I: 3.00700 Decimal Present… Pacific (left)… 6 sig. figs. Ex. II: 300,700 Decimal Absent… Atlantic (right)… 4 sig. figs. (the last 2 zeros are PLACE HOLDERS)**REVIEW**Determine how many significant figures are in each of the following measurements. • 0.0034050 L ___________ • 33.600 m ___________ • 7500.0 g ___________ • 47,900 mm ___________ • 7,000,000,001 miles ___________ • 8.07 Hz ___________ 5 (the first 3 zeros are PLACE HOLDERS) 5 5 3 (the last 2 zeros are PLACE HOLDERS) 10 3**More practice…**Round the following measurements off so that they each contain 3 significant figures. • 366.2 L ___________ • 9,047,022 mg ___________ • 12.76 g ___________ • 999.9 J ___________ 366 L 9,050,000 mg 12.8 g 1.00 x 103 J Notice this one must be in scientific notation to have 3 sig. figs.**Significant Figures in Calculations**When multiplying and dividing, limit and round to the least number of significant figures in any of the factors. Example: 23.0 x 432 x 19 = 188,784 = 190,000 The answer is expressed as 190,000 or 1.9 x 105 since 19 has only two sig. figs.**Significant Figures in Calculations**When adding and subtracting, limit and round your answer to the least number of decimal places in any of the numbers involved in the calculation. Example: 123.25 + 46.0 +86.257 = 255.507 = 255.5 The answer is expressed as 255.5 since 46.0 has only one decimal place.**REVIEW**Perform the prescribed operations. Round your answers to the proper # of sig. figs. • 36.57 m / 3.21 s = ___________ • 41.376g + 13.3g + 42.9g=___________ • 5.67 m x 13.44 m ___________ • (5.83 m/ 2.67 s) /2.1 s ___________ • 9.374 V x 6 ___________ 11.4 m/s 97.6 g 76.2 m2 1.0 m/s2 60 V From now on, we will round all our answers to the correct # of significant figures.**EXTRA REVIEW**• Using a calculator for EXPONONETS (EE, EXP or x10x button) • Example 1: (5.02 x 10-3) x (6.3369 x 105) = 3181.1238 *put in correct sig figs = 3 sig figs = 3180 or 3.18 x 103**Example 2 (use EE button!)**• (2.99 x 106) x (2.334 x 10-3) = = 6978.66 • 3 sig figs • 6980**DIMENSIONAL ANALYSIS**• How old are you in seconds? • Go from number of years to number of seconds. EX: 15 years old _____ seconds old. To do this, you need to use CONVERSION FACTORS (a ratio of equivalent values used to express the same quantity in different units)**Given Information: NOTETAKERS**General Format... given going to = X coming from**GIVEN INFORMATION**1 kildurkin = 18 gallons 2 farkins = 1 kildurkin 1 hogshead = 63 gallons 1 barrel = 3.3 bushels 1 bushel = 8 gallons**Make a UNIT CONVERSION MAP**Draw connections between the units in the conversion factors… (as you draw connections, check that conversion factor off the list) It’s kind of like a road map…**hogshead**kildurkins farkins gallons barrel bushel**Dimensional Analysis**Performing these conversions is a lot like going on a road trip.**ROAD TRIP!!!**Let’s say you want to travel from Oracle Jct to Casa Grande... You must travel through Tucson… a two part trip.**Rule: You need a map. Sometimes the map can be in your**head. But, not at first. (show all work!!)**Let’s calculate**• Convert 14 gallons to kildurkins**Now you try one. How many farkins is**3.00 bushels? End Here hogshead kildurkins farkins gallons Start Here barrel bushel This will require 3 Conversions.**farkins**bushels gallons kildurkins 8.0 gallons 1.0 kildurkin 2.0 farkins 3.00 bushels X X X 1.0 bushel 18 gallons 1.0 kildurkin = 2.67 farkins