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Honors Chemistry. Chapter 1 The Study of Change. 1.1 – 1.2 Chemistry. The study of matter and the changes it undergoes Structure and properties of matter Macroscopic vs Microscopic Structure (microscopic) determines properties (macroscopic). 1.3 Scientific Method.
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Honors Chemistry Chapter 1 The Study of Change
1.1 – 1.2 Chemistry • The study of matter and the changes it undergoes • Structure and properties of matter • Macroscopic vs Microscopic • Structure (microscopic) determines properties (macroscopic)
1.3 Scientific Method • Systematic approach to research • Based on data gathered by observation • Qualitative – general observations • Quantitative – numeric data • Evolution of ideas • Hypothesis – tentative explanation; testable • Theory – unifying principle that explains observations • Scientific Law – mathematical relationship
1.4 Classification of Matter • Matter – anything with mass and volume • Substance – matter with definite composition and distinct properties • Element – cannot be separated into simpler substances (ie, only one type of atom present) • Examples: aluminum, gold, sulfur, oxygen, neon • Compound – two or more elements chemically combined in fixed proportions • Examples: water, sulfuric acid, rust, baking soda
1.4 Classification of Matter • Mixture – combination of two or more substances which retain their identities • Homogeneous mixture – composition of mixture is uniform throughout • Examples: saltwater, air, metal alloys • Heterogeneous mixture – composition is not uniform; phase boundaries • Examples: salt and pepper, oil and water, salad dressing
1.5 States of Matter sublimation vaporizing melting solid liquid gas condensing freezing deposition
1.6 Properties of Matter • Physical property • can be observed without changing the identity of the substance • Physical change • remains the same substance • Extensive property • Depends only on the amount of matter present • Intensive property • Depends on the type of matter present
1.6 Properties of Matter • Chemical property • Property involving reactions with other substances • Chemical change • New substance is produced • Classify the following properties: • Color, mass, flammability, solubility, density • Classify the following changes: • Rusting, cutting, melting, burning, dissolving
1.7 SI Units • Système Internationale d’Unites • International System of Units
1.7 SI Conversions m T G M unit d c m n p k h da 3 decimal places 3 decimal places 1 decimal place Multiply number of decimal places by the dimensionality of the unit Some Practice: 0.173 25 000 17.3 cm = ______ m 0.025 kg = ______ mg 986 0.000 058 7 0.986 dm3 = ______ cm3 587 nm = __________ cm
1.7 Derived Units • Mathematical combinations of base units • Area A=lw m·m = m2 • Volume V = lwh m · m · m = m3 • dm3 = Liter cm3 = mL • Density r = m/V kg/m3, g/cm3, g/mL • Mass vs. Weight • Mass = amount of matter = kg • Weight = force of gravity = N
1.7 Temperature Scales Fahrenheit Celsius Kelvin Boiling Point 212oF 100oC 373.15 K Human bodytemp = 100oF Freezing Point 32oF 0oC 273.15 K Coldest temp in lab = 0oF Absolute Zero -460oF -273.15oC 0 K
1.7 Temperature Conversions • Celsius-Kelvin: offset by 273.15o • K = oC + 273.15 • oC = K – 273.15 • Celsius-Fahrenheit • Offset by 32oF • Different sized degrees: 9Fo = 5Co • oC = 5/9 (oF - 32) • oF = 9/5oC + 32 • Convert 98.6oF to oC and to K
1.8 Scientific Notation • m x 10n • 1 ≤ m < 10 • Exponentiation multiply exponents • Multiplication Add exponents • Division Subtract exponents • Addition/Subtraction must have same exponent
1.8 Significant Digits Digits which were actually measured, as opposed to placeholder zeroes Consider...how long is the blue rectangle? 1 2 3 4 5 cm Estimate the next digit Read 2 cm 2.4 cm ± 0.1 cm Let’s use a better ruler uncertainty in measurement dx measurement x Now how long is the rectangle? 2.43 cm ± 0.01 cm Implied ±1 on last digit of all measurements unless told otherwise
1.8 Significant Digits • Rules of thumb to deal with calculations involving significant digits • Addition/Subtraction • Round to the decimal place of the least precise value • Multiplication/Division • Round to the number of digits of the least precise value • Answers must be rounded properly!
1.8 Relative Error • Compare uncertainty to measurement • dx RE = ------ x • Often expressed as a percent • With laboratory data, dx is found by comparing experimental result to theoretical expectations • | xth – xexp | RE = --------------- xth
1.8 Accuracy and Precision • Accuracy • how close a measurement is to the correct value • How close were you to the bull’s eye? • Precision • how closely a set of values agree with each other • Were your shots clustered or scattered? • Let’s measure the bp of water 3 times • Accurate but not precise: 96oC, 101oC, 104oC • Precise but not accurate: 57.2oC, 56.8oC, 57.1oC
1.9 Dimensional Analysis • Technique for solving problems by treating units of measure as algebraic quantities • Set up conversion factors • 18 in = __________ ft • We know 1 ft = 12 in • 18 in 1 ft------- x -------- = 1 12 in 1.5 ft
1.9 Dimensional Analysis • Convert the speed of light (3.00 x 108 m/s) to miles / hour. • 3.00 x 108 m 1 km 1 mile 3600 s------------------ x ---------- x ---------- x -------- 1 s 1000 m 1.6 km 1 hr • = 6.8 x 108 mi/hr • 2 sig dig because of km – mile conversion • That wasn’t so bad, was it?
