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Chapter 1 – The Nature of Science

Chapter 1 – The Nature of Science. What is Science?. Science is a method for studying the natural world. It is a process that uses observation and investigation to gain knowledge about events in nature. Scientific explanations help you understand the natural world.

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Chapter 1 – The Nature of Science

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  1. Chapter 1 – The Nature of Science Chem-Phys, Chapter 1 Page 1

  2. What is Science? • Science is a method for studying the natural world. It is a process that uses observation and investigation to gain knowledge about events in nature. • Scientific explanations help you understand the natural world. • Example: Heat is the vibration of particles in a substance – not an invisible fluid (as thought in the 18th century). Chem-Phys, Chapter 1 Page 2

  3. Main Categories of Science • Life science (biology) deals with living things • Earth science investigates Earth and space • Physical science (chemistry and physics) deals with matter and energy Chem-Phys, Chapter 1 Page 3

  4. Investigations • Observing something occur (record observations in a journal) • Set up an experiment to test something • Build a model of something that occurs in nature and then test the model to see how it reacts. Chem-Phys, Chapter 1 Page 4

  5. Question • Why do scientific explanations change? Chem-Phys, Chapter 1 Page 5

  6. Scientific Method • The scientific method is an organized set of steps used to study an event in nature. • It consists of six general steps. (Next slide). Chem-Phys, Chapter 1 Page 6

  7. Scientific Method • State the problem • Gather information • Form a hypothesis • Test the hypothesis • Analyze data • Draw Conclusions Chem-Phys, Chapter 1 Page 7 hypothesis supported Hypothesis not supported

  8. Stating a Problem • A statement of a person who wonders “how” or “why” something occurs. • Examples: • Why does a ball fall to earth when released? • How does my i-Pod work? Chem-Phys, Chapter 1 Page 8

  9. Gathering Information • What is already known about the problem? • Library? • Experts? Chem-Phys, Chapter 1 Page 9

  10. Hypothesis and Experiment • A hypothesis is a proposed explanation. • An experiment is a way of testing a hypothesis under controlled conditions. Chem-Phys, Chapter 1 Page 10

  11. Variables • A variable is a measurable quantity that can have more than a single value. • An independent variable is controlled by the scientist to see what the effect will be. • A dependent variable has a value which depends on values of the other variables in the system. Chem-Phys, Chapter 1 Page 11

  12. Variables • Independent variables answer the question "What do I change?" • Dependent variables answer the question "What do I observe?" • Controlled variables answer the question "What do I keep the same?" • Extraneous variables answer the question "What uninteresting variables might mediate the effect of the IV on the DV?" Chem-Phys, Chapter 1 Page 12

  13. Variables • if one were to measure the influence of different quantities of fertilizer on plant growth, the independent variable would be the amount of fertilizer used (the changing factor of the experiment). The dependent variables would be the growth in height and/or mass of the plant (the factors that are influenced in the experiment) and the controlled variables would be the type of plant, the type of fertilizer, the amount of sunlight the plant gets, the size of the pots, etc. (the factors that would otherwise influence the dependent variable if they were not controlled). Chem-Phys, Chapter 1 Page 13

  14. Variables • In a study of how different doses of a drug affect the severity of symptoms, a researcher could compare the frequency and intensity of symptoms (the dependent variables) when different doses (the independent variable) are administered, and attempt to draw a conclusion. Chem-Phys, Chapter 1 Page 14

  15. Constants and Controls • A factor that does not change when other variables change is called a “constant.” • A control is a standard by which other test results can be compared. Question: Why is a control used in an experiment? Chem-Phys, Chapter 1 Page 15

  16. Analyzing Data, Drawing Conclusions • Analyzing Data - All data must be recorded and organized. • Drawing Conclusions - Based on the analysis of the data, you decide whether or not your hypothesis is supported. • If not: Form a new hypothesis • If so: Continue to test the hypothesis Chem-Phys, Chapter 1 Page 16

  17. Being Objective • Scientists must try to record the observations just as they are and not let what they expect affect the recorded data. • Bias occurs when what the scientist expects changes how the results are viewed. • https://www.youtube.com/embed/d6cV6568qjQ • https://www.youtube.com/embed/MV8lSmIo4Ac Chem-Phys, Chapter 1 Page 17

  18. Models • A model represents an idea, event, or object to help people better understand it. • Examples • Globe • House plans • Model airplane • Toy train Chem-Phys, Chapter 1 Page 18

  19. Theories and Laws • A scientific theory is an explanation of things or events based on many observations and investigations. • A scientific law describes what will happen in nature and seems to be true all the time. A law explains what will happen under certain conditions but does not explain why or how it happens. Chem-Phys, Chapter 1 Page 19

  20. Technology • Technology is the application of science to solve problems and help people. • Examples: • Wide screen TV • Antibiotics • Cell phones • Photocopiers Chem-Phys, Chapter 1 Page 20

  21. Chapter 1, Section 1 Review • What are the steps that scientists often use to solve problems? • Why do scientists use variables? • What are the similarities and differences between science and technology? Chem-Phys, Chapter 1 Page 21

  22. Standards • A standard is an exact quantity that people agree to use to compare measurements. • Examples: • Time - Atomic clock • Length - distance light travels in a precise time interval. Chem-Phys, Chapter 1 Page 22

  23. Stating a Measurement In every measurement there is a • Number followed by a • Unit from a measuring device The number should also be as precise as the measurement!

  24. SI Base Units Chem-Phys, Chapter 1 Page 24

  25. Common SI Prefixes Chem-Phys, Chapter 1 Page 25

  26. UNITS OF MEASUREMENT Use SI units — based on the metric system Length Mass Volume Time Temperature Meter, m Kilogram, kg Liter, L Seconds, s Celsius degrees, ˚C kelvins, K

  27. English and Metric Conversions • If you know ONE conversion for each type of measurement, you can convert anything! • You must memorize and use these conversions: • Mass: 454 grams = 1 pound • Length: 2.54 cm = 1 inch • Volume: 0.946 L = 1 quart

  28. Learning Check An adult human has 4.65 L of blood. How many gallons of blood is that? Unit plan: L qt gallon Equalities: 1 quart = 0.946 L 1 gallon = 4 quarts Your Setup:

  29. Equalities State the same measurement in two different units length 10.0 in. 25.4 cm

  30. Mass vs. Weight • Mass: Amount of Matter (grams, measured with a BALANCE) • Weight: Force exerted by the mass, only present with gravity (pounds, measured with a SCALE) Can you hear me now?

  31. Some Tools for Measurement Which tool(s) would you use to measure: A. temperature B. volume C. time D. weight

  32. Learning Check Match L) length M) mass V) volume ____ A. A bag of tomatoes is 4.6 kg. ____ B. A person is 2.0 m tall. ____ C. A medication contains 0.50 g Aspirin. ____ D. A bottle contains 1.5 L of water. M L M V

  33. Learning Check What are some U.S. units that are used to measure each of the following? A. length B. volume C. weight D. temperature

  34. Metric Prefixes • Kilo- means 1000 of that unit • 1 kilometer (km) = 1000 meters (m) • Centi- means 1/100 of that unit • 1 meter (m) = 100 centimeters (cm) • 1 dollar = 100 cents • Milli- means 1/1000 of that unit • 1 Liter (L) = 1000 milliliters (mL)

  35. Metric Prefixes

  36. Metric Prefixes

  37. Learning Check 1. 1000 m = 1 ___ a) mm b) km c) dm 2. 0.001 g = 1 ___ a) mg b) kg c) dg 3. 0.1 L = 1 ___ a) mL b) cL c) dL 4. 0.01 m = 1 ___ a) mm b) cm c) dm

  38. O—H distance = 9.4 x 10-11 m 9.4 x 10-9 cm 0.094 nm Units of Length • ? kilometer (km) = 500 meters (m) • 2.5 meter (m) = ? centimeters (cm) • 1 centimeter (cm) = ? millimeter (mm) • 1 nanometer (nm) = 1.0 x 10-9 meter

  39. Learning Check Select the unit you would use to measure 1. Your height a) millimeters b) meters c) kilometers 2. Your mass a) milligrams b) grams c) kilograms 3. The distance between two cities a) millimeters b) meters c) kilometers 4. The width of an artery a) millimeters b) meters c) kilometers

  40. Conversion Factors Fractions in which the numerator and denominator are EQUAL quantities expressed in different units Example: 1 in. = 2.54 cm Factors: 1 in. and 2.54 cm 2.54 cm 1 in.

  41. Question • How many meters in a kilometer? Chem-Phys, Chapter 1 Page 41

  42. Factor Label Method • Express 4.5 kg as grams • Begin by Expressing as a Fraction: 4.5 kg 1 • Identify Conversion Factor: 1 kg = 1000 grams • Express as a Fraction: Chem-Phys, Chapter 1 Page 42 1 kg 1000 g 1 = --------------- or -------------- 1000 g 1 kg

  43. Factor LabelContinued • Write Equation Including Proper Factor • Cancel Units • Multiply Numbers to Get Final Result Chem-Phys, Chapter 1 Page 43 4.5 kg 1000 g --------- x -------------- = 4500 g 1 1 kg

  44. Factor Label Steps • Express as a Fraction • Identify Conversion Factor • Express Conversion Factor as Two Fractions • Select Proper Factor (units in denom.) • Write Equation Including Proper Factor • Cancel Units • Multiply Numbers to Get Final Result Chem-Phys, Chapter 1 Page 44

  45. Volume • The amount of space occupied by an object is call its volume. • Volume – length x width x height • Units – length cubed • cm3 • M3 • 1 cm3 = 1 mL (1 milliliter) Chem-Phys, Chapter 1 Page 45

  46. Density • Mass is the quantity of matter in an object (SI unit: kg). • Density is the mass of an object divided by the volume of the object. (g/cm3) • Density is an example of derived units obtained by combining different SI units. Chem-Phys, Chapter 1 Page 46

  47. Solution 2) Placing the mass and volume of the osmium metal into the density setup, we obtain D = mass = 50.00 g = volume 2.22 cm3 = 22.522522 g/cm3 =22.5 g/cm3

  48. Volume Displacement A solid displaces a matching volume of water when the solid is placed in water. 33 mL 25 mL

  49. Learning Check What is the density (g/cm3) of 48 g of a metal if the metal raises the level of water in a graduated cylinder from 25 mL to 33 mL? 1) 0.2 g/ cm3 2) 6 g/m3 3) 252 g/cm3 33 mL 25 mL

  50. Learning Check Which diagram represents the liquid layers in the cylinder? (K) Karo syrup (1.4 g/mL), (V) vegetable oil (0.91 g/mL,) (W) water (1.0 g/mL) 1) 2) 3) K W V V K W W V K

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