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Understanding the Scientific Method: A Logical Approach to Problem Solving

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This chapter explores the scientific method as a logical approach to solving problems through observation and data collection. It outlines how to formulate and test hypotheses, and how to establish theories based on empirical evidence. Key concepts include the distinction between qualitative and quantitative data, the importance of controlling variables, and the role of models and theories in science. The chapter also introduces the metric system, derived SI units, and emphasizes accuracy, precision, and significant figures in scientific measurements.

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Understanding the Scientific Method: A Logical Approach to Problem Solving

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Presentation Transcript

  1. Chapter 2 Scientific Method

  2. Scientific Method • Scientific method- logical approach to solving problems by observing & collecting data, formulating hypotheses, testing hypotheses, formulating theories supported by data • Examples of problems… • Observable data • Qualitative = descriptive (turn pink) • Quantitative = numerical (1 gram)

  3. Data • We cannot observe everything all at once, so we focus on a system • System- specific portion of matter chosen for study (ex. Reaction in a test tube) • Once we obtain data, we can establish patterns • Patterns can be made into scatter plots, bar graphs, pie charts, etc.

  4. Hypothesis • Once we have looked for patterns, we form a hypothesis • Hypothesis- testable statement in the form of “if…then…” • Then we have to test the hypothesis • Control(s)- stay constant (placebo) • Variable(s)- change, only changed one at a time • If wrong, change or drop hypothesis (might start over)

  5. Hypothesis (con.) • If correct, explain through models • Model- explains how events occur or are related in a visual, verbal, or mathematical way • Theory- broad generalization that explains group of facts or events • Publish results (letters, scholarly journals, blog, word of mouth)

  6. Metric System • SI, or SystèmeInternationaled’Unités (French) • Base units • Length (lowercase L) = meter (m) • Mass (m) = kg (kilogram) • Time (t) = second (s) • Temperature (T) = Kelvin (K) • Amount of substance (n) = mole (mol) • Electric current (I) = ampere (A) • Luminous intensity (Iv) = candela (cd)

  7. Metric prefixes • Mega (M) = 10 6 • Kilo (k) = 10 3 • Hecto (h) = 10 2 • Deka (da) = 10 1 • Deci (d) = 10 -1 • Centi (c) = 10 -2 • Milli (m) = 10 -3 • Micro (µ) = 10 -6 • Practice problems on board

  8. Mass vs. Weight • Mass = amount of matter • Weight = amount of gravity pull • On moon, gravity 1/6 that of Earth • Didn’t lose mass, lost weight

  9. Derived SI units • Combinations of base units • Area (A) = lxw = m2 or cm2 • Volume (V) = lxwxh = m3 or cm3 • Density (D) = kg/m3 or g/cm3 or g/mL • Molar Mass (MM) = kg/mol • Energy (E) = Joule (J)

  10. Accuracy vs. Precision • Accuracy- close to accepted value • Precision- close to measurements made in same way • Drawings on board

  11. Percent Error • Goal = 0 • (Experimental – Accepted)/(Accepted) x 100 • Problems on board

  12. Significant figures • All digits but last one certain • Rules • Nonzero = significant • Zero in between nonzero (2002) = significant • Zero in front of nonzero = not significant • Zero at end of number and to right of decimal = significant • Ex. 2000 = 1 sig, 25.00 = 4 sig, .0001 = 1 sig • Examples on board

  13. Rounding • 1->4, round down • 6->9, round up • 3.5->4 • 4.5->4 • Sig + or – Sig= same # of decimals • Sig x or / Sig = same # of sig digits • Examples on board

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