Chapter 1. Introduction: Matter and Measurement

Transcription

1 Chapter 1 Introduction: Matter and Measurement

2 Steps in the Scientific Method 1. Observations - quantitative - qualitative 2. Formulating hypotheses - possible explanation for the observation 3. Performing experiments - gathering new information to decide whether the hypothesis is valid

3 Outcomes Over the Long-Term Theory (Model) -!A set of tested hypotheses that give an overall explanation of some natural phenomenon. Natural Law - The same observation applies to many different systems - Example - Law of Conservation of Mass

4 The Scientific Method

5 01_03 Observation Hypothesis Experiment Theory (model) Law Theory modified as needed Prediction Experiment

6 Law v. Theory A law summarizes what happens; a theory (model) is an attempt to explain why it happens.

7 Nature of Measurement Measurement - quantitative observation consisting of 2 parts Part 1 - number Part 2 - scale (unit) Examples: 20 grams Joule seconds

8 International System (le Système International) Based on metric system and units derived from metric system.

9 The Fundamental SI Units Physical Quantity Name Abbreviation Mass kilogram kg Length meter m Time second s Temperature Kelvin K Electric Current Ampere A Amount of Substance mole mol Luminous Intensity candela cd

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11 Uncertainty in Measurement A digit that must be estimated is called uncertain. A measurement always has some degree of uncertainty.

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13 01_08 Buret ml ml

14 Precision and Accuracy Accuracy refers to the agreement of a particular value with the true value. Precision refers to the degree of agreement among several elements of the same quantity.

15 Figure 01.24a

16 Figure 01.24ab

17 Figure 01.24

18 Types of Error Random Error (Indeterminate Error) - measurement has an equal probability of being high or low. Systematic Error (Determinate Error) - Occurs in the same direction each time (high or low), often resulting from poor technique.

19 Rules for Counting Significant Figures - Overview 1. Nonzero integers 2. Zeros!!- leading zeros!!- captive zeros!!- trailing zeros 3. Exact numbers

20 Rules for Counting Significant Figures - Details Nonzero integers always count as significant figures has 4 sig figs.

21 Rules for Counting Significant Figures - Details Zeros -!Leading zeros do not count as significant figures has 3 sig figs.

22 Rules for Counting Significant Figures - Details Zeros - Captive zeros always count as significant figures has 4 sig figs.

23 Rules for Counting Significant Figures - Details Zeros -! Trailing zeros are significant only if the number contains a decimal point has 4 sig figs.

24 Rules for Counting Significant Figures - Details Exact numbers have an infinite number of significant figures. 1 inch = 2.54 cm, exactly

25 Rules for Significant Figures in Mathematical Operations Multiplication and Division: # sig figs in the result equals the number in the least precise measurement used in the calculation = (2 sig figs)

26 Rules for Significant Figures in Mathematical Operations Addition and Subtraction: # decimal places in the result equals the number of decimal places in the least precise measurement = (3 sig figs)

27 Dimensional Analysis Proper use of unit factors leads to proper units in your answer. 1 in = 2.54 cm 1 pound = g 1 gallon = L

28 Figure UNEOC

29 Figure UN

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31 Dimensional Analysis 1.49 (b) The recommended adult dose of Elixophyllin, a drug used to treat asthma, is 6 mg/kg of body mass. Calculate the dose in milligrams for a 150-lb person. (1 lb= g)

32 Temperature Celsius scale = C Kelvin scale = K Fahrenheit scale = F

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34 Temperature T K = T + C T F 9 F = T C 5 C + 32 F

35 Figure 01.17

36 Density Density is the mass of substance per unit volume of the substance: density = mass volume

37 Table 01.06

38 Dimensional Analysis Proper use of unit factors leads to proper units in your answer. 1 in = 2.54 cm 1 pound = g 1 gallon = L

39 Using Density Determine the thickness of a sheet of platinum, in millimeters, that is a square 1.25 in. per side. The piece of platinum weighs grams. (The density of Pt is g cm -3 )

40 Matter: Anything occupying space and having mass.

41 The Big Bang

42 Classification of Matter Three States of Matter: Solid: rigid - fixed volume and shape Liquid: definite volume but assumes the shape of its container Gas: no fixed volume or shape - assumes the shape of its container

43 Figure 01.04

44 Types of Mixtures Mixtures have variable composition. A homogeneous mixture is a solution (for example, vinegar) A heterogeneous mixture is, to the naked eye, clearly not uniform (for example, a bottle of ranch dressing)

45 Mixtures and Compounds

46 Pure Substances Can be isolated by separation methods: - Chromatography - Filtration - Distillation

47 Figure 01.14

48 Figure 01.12

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50 Electrolysis of Water

51 Figure 01.07

52 Compound or Element Compound: A substance with a constant composition that can be broken down into elements by chemical processes. Element: A substance that cannot be decomposed into simpler substances by chemical means.

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54 01_15 Matter Heterogeneous mixtures Physical methods Homogeneous mixtures (solutions) Physical methods Pure substances Compounds Chemical methods Elements Atoms Nucleus Electrons Protons Neutrons Quarks Quarks

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56 Elemental Composition

57 End