Chapter 1 Chemical Foundations DE Chemistry Dr. Walker

Scientific Method You should be familiar with the top by now… …maybe not so much with the bottom section. A law summarizes what happens; a theory (model) is an attempt to explain why it happens.

Why Units Are Important

Units Of Measurement SI system, based on metric Based on fundamental units, prefixes used to change size

Common Prefixes Be familiar with the units shown in blue above

Uncertainties In Measurement Notice in the measurements above that you may estimate one digit beyond the reading of the instrument.

Uncertainty Precision (left) – reproducibility of measurement Accuracy (right) – Proximity to known value

Uncertainty Errors Random Errors (indeterminate errors) Measurements may be high or low Causes: Interpretation of the uncertain digit Procedural ineptness Systematic Errors Always occur in the same direction Caused by poor measurement calibration gun sight set too high/low balance improperly zeroed thermometer improperly marked

Sig Figs – The Return… Involve measurements The Rules… Exact Numbers Nonzero digits….always count Captive zeros….always count Trailing zeros…..only count with a decimal Leading zeros….don’t count Exact Numbers Not involved in measurements

Rules For Operations All calculations in this course should use proper sig figs.

Dimensional Analysis…The Real Way! Similar to the t-square method we used last year. Notice the placement of the numbers and the cancelling units are exactly the same. There just isn’t a “T”

Dimensional Analysis…The Real Way! Multi-step example Three steps 1 2 3

Temperature Scales In science, typically Celsius or Kelvin is used Celsius + 273 = Kelvin Celsius = (Farenheit – 32) x 5/9 Farenheit = (Celsius x 9/5) + 32

Density D = m/v Could be in g/mL or g/cm3 for liquids (these are equivalent) Usually in g/L for gases (molar mass/22.4 at STP)

Classification Of Matter Anything that occupies space and has mass States of Matter Solids - rigid, fixed volume and shape Liquids - definite volume, no specific shape Gases - no fixed volume or shape, highly compressible Plasma – High temperature, ionized phase of matter; found in stars

Mixtures Mixtures - Matter of variable composition Heterogeneous mixtures Having visibly distinguishable parts Homogeneous mixtures (solutions) Having visibly indistinguishable parts Components of mixtures can be separated by physical means Distillation (boiling point) Filtration (particle size) Chromatography (affinity for solid phase)

Properties Of Matter Intensive Physical Properties Not quantity dependent Density Phase changes (bp, mp) Hardness Color Extensive Physical Properties Quantity Dependent Mass Volume Length

Organization Of Matter

Separating Mixtures Chromatography Distillation

Separating Compounds Compounds can be decomposed to elements only through chemical changes. 2 H2O  2 H2 + O2 H2O2  H2 + O2 2 P2O5  4 P + 5 O2

Problem Set Zumdahl – Chapter 1 # 28, 30, 32, 38, 48, 52, 60, 64, 70, 76