Chapter 1 - Introduction & Scientific Measurement

Course Information

  • Course Title: Scientific Measurement

  • Instructor: Prof. Chris Li

  • Institution: University at Buffalo, The State University of New York

  • Class Schedule:

    • Tuesday, Thursday 9:30 – 10:50 am

  • Office Hours:

    • Tuesday, Thursday 12:30 – 1:30 pm or by appointment

Course Materials

  • Main Materials:

    • Achieve for Interactive General Chemistry

    • iClicker for in-class participation

    • Computer for taking exams

  • Assessments:

    • Homework (11 assignments)

    • Quizzes (4 quizzes)

    • Recitations (2 sessions)

    • Midterm and Final exams

Measurement Importance

  • Correct measurement of ingredients is crucial for effective chemistry experimentation, similar to precise baking recipes.

Units of Measurement

Base Units

  • Measurement Conversions:

    • 1 kg = 1000 g

    • 1 m = 100 cm

    • 1 gigabyte = 1000 megabytes

Derived Units

  • Density Calculation:

    • Volume = 2m x 2m x 2m = 8 m³

  • Area Measurement:

    • Area = 3 cm x 3 cm = 9 cm²

Measurement Comparisons

Physical Quantity

English Unit

SI Unit

Length

1 in.

2.540 cm

1 ft

0.3048 m

1 mile

1.609 km

Mass

1 lbm

0.4536 kg

Force

1 lbf

4.448 N

Temperature

TF = 5/9(TF - 32) + 273.15

Pressure

1 lb/in²

6.895 x 10^3 Pa

Power

1 Btu/h

0.2929 W

Magnetic Field

1 gauss

1.000 x 10^-4 tesla

Measurement and Uncertainty

  • Measurement can have uncertainties; estimates should extend one digit beyond the smallest division marked.

  • Exact Numbers include constants like 60 seconds in a minute, which have no uncertainty.

Significant Figures

  • Rules:

    1. Non-zero digits are significant.

    2. Zeros between non-zero digits are significant.

    3. Leading zeros are not significant.

    4. Trailing zeros after a decimal point are significant.

    5. Trailing zeros before a decimal point may be ambiguous (can be significant or not).

  • Example Numbers:

    • 107 (3 sig figs), 4.502 (4 sig figs), 0.11 (2 sig figs)

Performing Calculations with Significant Figures

  • Addition/Subtraction: Result should have the fewest decimal places.

  • Example:

    • 6.52 + 8.1 = 14.62 -> 14.6 (rounded to one decimal place)

  • Multiplication/Division: Result should have the fewest significant figures.

  • Example:

    • 4.6 x 7.64 = 35.144 -> 35 (rounded to two significant figures)

Dimensional Analysis

  • Measurement includes both a number and a unit.

  • Example:

    • Earning from working hours can be calculated: 20 hours x $15/h = $300

    • Spending can also be calculated: $300/$50/game = 6 games

Temperature Conversion

  • Kelvin = Celsius + 273.15

  • Fahrenheit to Celsius: TF = 9/5 TC + 32

  • Example:

    • Room temperature 23 °C = 296.15 K; = 73.4 °F

Summary of Key Concepts

  • Importance of measurement in chemistry: Unit, uncertainty, significant figures, and dimensional analysis for unit conversion.