Chapter 1: What is Science? PDF

Chapter 1 What is Science? © 2022 McGraw Hill. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw Hill. Overview...

Chapter 1 What is Science? © 2022 McGraw Hill. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw Hill. Overview Quantitative The nature of science: descriptions: The Scientific Method. Objects and properties. Explanations and Quantifying properties. investigations. Measurement systems. Scientific laws. Standard metric units. Models and theories. Metric prefixes. Understanding from measurement. Objects and properties Objects - things that can be seen or touched. Properties - qualities or attributes characteristic of an object. Referents - comparative properties in other, more familiar objects (Examples: “sky blue,” “lemon yellow”). Problem - language can be subjective, ambiguous and ultimately circular! Quantifying properties Measurement: uses quantitative referents - “units.” Three steps: Comparing the referent unit to the property being described. Following a procedure specifying how the comparison is done. Counting how many standard units describe the property under consideration. Essential - a number and name for the referent unit. Measuring a book with a paper clip Procedure: Make mark at bottom of book. Place aligned clip above mark and make second mark. Continue to top. Record number and units: “7 clip lengths.” Measurement systems (based upon standardized units) English system: Metric (SI) system: Many units based Established in 1791. upon parts of the 7 base units: human body. Meter (m). Different units are not Kilogram (kg). systematically related. Second (s). Ampere (A). Kelvin (K). Mole (mol). Candela (cd). All other units derive from these. The same distance can be described using different units 50 leagues 130 nautical miles 150 miles 158 Roman miles 1,200 furlongs 12,000 chains 48,000 rods 452,571 cubits 792,000 feet Standard metric units for the fundamental properties Property Unit Symbol Length meter m Mass kilogram kg Time second s Electric current ampere A Temperature kelvin K Amount of substance mole mol Luminous intensity candela cd Metric prefixes 1 Prefix Symbol Meaning tera- T 1012 (1,000,000,000,000 times the unit ) giga- G 109 (1,000,000,000 times the unit ) mega- M 106 (1,000,000 times the unit ) kilo- k 103 (1,000 times the unit ) hecto- h 102 (100 times the unit ) deka- da 101 (10 times the unit ) Unit deci- d 10−1 ( 0.1 of the unit ) centi- c 10−2 ( 0.01 of the unit ) milli- m 10−3 ( 0.001 of the unit ) micro- μ 10−6 ( 0.000001 of the unit ) nano- n 10−9 ( 0.000000001 of the unit ) pico- p 10−12 ( 0.000000000001 of the unit ) Metric prefixes 2 Understanding from measurement Data. Ratios and generalizations. The density ratio. Symbols and equations. Problem solving made easy. Data Measurement information used to describe: Objects. Conditions. Events. Changes. The density ratio Ratio of mass and volume. Intrinsic property (independent of quantity). Characteristic of a given material. “Weight density” = weight per unit volume. Symbols and equations Symbols: Represent quantities, measured properties. Equations: Mathematical relationships between properties. Describe properties; define concepts; specify relationships. Relationships and Constants Direct proportionality. Inverse proportionality. Numerical constants. Proportionality constants. Numbers play a major role in chemistry. 3.6 L V6 454 in3 V8 6.2 L V8 Many topics are quantitative (have a numerical value). These include units of measurement, quantities, significant figures, dimensional analysis. T (in °F) = 1.8T (in °C) + 32 T (in K) = T (in °C) + 273.15 Example: Mustard gas has a boiling point of 422.6 oF or 217 oC.  Converting Units of Temperature Example: A child suspected of consuming rat poison has a body temperature of 38.7°C, and normal body temperature is 98.6°F. Does the child have a fever? What is the child’s temperature in kelvins? Solution: We have to convert °C to °F to find out if the child has a fever. We can then use the °C to Kelvin relationship to find the temperature in Kelvin. SOLUTION: T (in °F) = 1.8T (in °C) + 32 Converting from °C to °F 1.8 (38.7 °C) + 32 = 69.7 + 32 = 101.7 °F Yes, the child has a fever. Converting from °C to K 38.7 °C + 273.15 = 311.8 K Problem Solving: Unit Conversions Many activities in the laboratory require converting a quantity from one unit to another. Learning Objective: Use the factor-label method (conversion factors) to solve a problem and check the result to ensure that it makes sense chemically and physically. Equations are set up so that unwanted units cancel and only the desired units remain. Starting Quantity × Conversion Factor = Equivalent Quantity  Example: 26.22 miles is equivalent to how many kilometers?  The conversion factor is an expression of the numerical relationship between two units. Equations are set up so that unwanted units cancel and only the desired units remain. Starting Quantity × Conversion Factor = Equivalent Quantity Problem Solving: Unit Conversions Units are treated like numbers and can thus be multiplied and divided. Set up an equation so that all unwanted units cancel. Problem Solving: Unit Conversions and Estimating Answers STEP 1: Identify the information given, including units. STEP 2: Identify the information needed in the answer, including units. STEP 3: Find the relationship(s) between the known information and unknown answer, and plan a series of steps for getting from one to the other. STEP 4: Solve the problem.  The Nature of Science Beginnings approximately 300 years ago: Associated with Galileo and Newton. Ancient natural philosophers - “thinking only.” Additional component here - understanding based upon experimental evidence. © 2022 McGraw Hill.  The Scientific Method Observe some aspect of nature. Propose an explanation for something observed. Use the explanation to make predictions. Test the predictions with experiments or more observations. Modify explanation as needed. Return to step 3. © 2022 McGraw Hill.  The Scientific Method - Example What are atoms made of? Negative electrons orbiting positive nuclei. Colliding two atoms will produce free electrons and nuclei. Colliding two atoms yielded electrons, protons and neutrons. Atoms are made of electrons orbiting nuclei made of protons and neutrons. Collide two atoms at higher energy. © 2022 McGraw Hill.  General scientific activities Collecting observations. Developing explanations. Testing explanations. © 2022 McGraw Hill.  Explanations and investigations Hypothesis - a tentative explanation for some observation. Experiment - recreation of an event or occurrence to test a hypothesis. Controlled experiment - comparing two situations with all factors alike except one. Control group - fixed set for comparison. Experimental group - differs from control group by one influencing factor. Patterns and experiment results are shared through scientific communication, including informal communication and published articles, which are checked and confirmed by other scientists. © 2022 McGraw Hill.  Laws, Models and Theories Laws: Important relationship observed to occur time after time. Descriptive in nature: Example: Charles’s Law - relationship between temperature and pressure in gases. Models: Description of a theory or idea that accounts for all known properties. o Can be physical, mathematical, based on a sketch or an analogy. o Useful for regimes too small or too vast for direct observation. Theories: o Broadly based set of working hypotheses. o Based upon considerable experimental support. o Form the framework of thought and experiment. © 2022 McGraw Hill.  Model of a rainbow A beautiful double rainbow! The result of the reflection and refraction of sunlight within individual raindrops. © 2022 McGraw Hill.  Pseudoscience Misleading and often absurd claims of scientific results. Tests: Academic and scientific background of claimant. History of review by scientific peers. Participation in scientific institutions and organizations. Claim published in peer-reviewed journal and independently validated by others. Does the claimant have something to gain. © 2022 McGraw Hill.