Chem 200 week 1 lecture 2

Physical Properties & Changes: Characteristics and alterations that do not change the underlying chemical or electrical structure of a substance (e.g., cutting, dissolving, melting, hardness, density, color).
Chemical Properties & Changes: Characteristics and alterations that involve changing the molecular structure of a substance (e.g., combustion, reaction with acids).
Extensive Properties: Quantities that depend directly on the amount of material present (e.g., mass, volume).
Intensive Properties: Quantities that do not depend on the amount of material present (e.g., density, concentration). Calculated by taking ratios of extensive properties.
Conservation of Mass: Principle stating that mass is conserved across all physical and chemical processes in Chem 200.

Components of a Reported Quantity: Every measured value requires a numerical value, a unit (scale), and a designated level of uncertainty.
Five Primary Base SI Units:
- Mass: kilogram ( $\text{kg}$ )
- Distance: meter ( $\text{m}$ )
- Time: second ( $\text{s}$ )
- Amount of Material: mole ( $\text{mol}$ ) ( $6 \times 10^{23}$ particles per mole)
- Temperature: Kelvin ( $\text{K}$ )
Additional Base SI Units: Ampere ( $\text{A} = 1\,\text{C/s}$ ) for electric current; Candela for radiant intensity.
Derived SI Units:
- Acceleration: $\text{m/s}^2$
- Force: Newton ( $\text{N} = \text{kg}\,\text{m/s}^2$ )
- Energy: Joule ( $\text{J} = \text{N}\,\text{m} = \text{kg}\,\text{m}^2/\text{s}^2$ )

Scientific Notation: standard representation where a single non-zero leading digit is written to the left of the decimal point multiplied by a power of $10$ . Used for numbers outside the range of $0.01$ to $1000$ (e.g., $5224.9$ written as $5.2249 \times 10^3$ ).
Non-SI Units in Chemistry:
- Angstrom ( $\text{\AA}$ ): $10^{-10}\,\text{m}$ , useful for atomic and chemical bond lengths.
- Degree Celsius ( $^\circ\text{C}$ ): Non-SI unit of temperature. Absolute zero corresponds to $0\,\text{K}$ . Conversion: $T(\text{K}) = T(^\circ\text{C}) + 273.15$ . Absolute temperature in Kelvin must be used whenever temperature is multiplied in an equation.
Volume Relations:
- $1\,\text{L} = 1\,\text{dm}^3 = 0.001\,\text{m}^3$
- $1\,\text{mL} = 1\,\text{cm}^3 = 10^{-3}\,\text{L}$

Types of Measurement Uncertainty:
- Random Error: Fundamental variations present in measurements; minimized by repeating trials and finding the average. Defines precision (reproducibility).
- Systematic Error: Flaws in experimental design or equipment leading to consistent bias. Defines accuracy (closeness to the true value).
Significant Figure Rules:
- All non-zero digits are significant.
- Zeros between non-zero digits are significant.
- Leading zeros are never significant.
- Trailing zeros are significant only if an explicit decimal point is present (e.g., $1200$ has 2 significant figures; $1.200 \times 10^3$ has 4 significant figures).
Calculations with Significant Figures:
- Addition / Subtraction: The answer is limited by the term with the least precise decimal place (furthest to the left).
- Multiplication / Division: The answer is limited by the term with the fewest total significant figures.

Density Formula: $\text{Density} = \frac{\text{Mass}}{\text{Volume}}$
Volume Example (Methane vs. Octane):
- Methane ( $\text{density} = 0.6470\,\text{g/L}$ ) volume for $105\,\text{g}$ : $\text{Volume} = \frac{105\,\text{g}}{0.6470\,\text{g/L}} = 162\,\text{L}$
- Octane ( $\text{density} = 0.686\,\text{g/cm}^3$ ) volume for $105\,\text{g}$ : $\text{Volume} = \frac{105\,\text{g}}{0.686\,\text{g/cm}^3 \times 1000\,\text{cm}^3/\text{L}} = 0.150\,\text{L}$
Density Determination Example (Chloroform):
- Given $50\,\text{mL}$ chloroform, flask mass = $137.3\,\text{g}$ , total mass = $211.9\,\text{g}$ : $\text{Mass of Chloroform} = 211.9\,\text{g} - 137.3\,\text{g} = 74.6\,\text{g}$ $\text{Density} = \frac{74.6\,\text{g}}{50\,\text{mL}} = 1.5\,\text{g/mL}$