Unit 1 Study Guide

Units of Measurement

• A standard system of measurement is important for communication and dissemination of information because it is universal. All scientists and researchers know and use this system of measurement. Using a standard system of measurement allows people to clearly communicate the data about an object/objects.

• The metric system is the standard system of measurement used by the entire world except for a few select countries (cough, cough, United States). SI measurements, or International System of Units, are used in the metric system.

  • Common units:

    • Mass: grams (g)

    • Length: meters (m)

    • Time: seconds (s)

    • Volume: liters (L)

  • Common SI prefixes:

    • Kilo - (k) - 1000

    • Hecta - (h) - 100

    • Deca - (D) - 10

    • Base - 0

    • Deci - (d) - 0.1

    • Centi - (c) - 0.01

    • Milli - (m) - 0.001

    • Micro - (µ) - 0.0001

• Dimensional Analysis - a way to convert between units. Turn into fractions, then cross-multiply to eliminate and add units that you want to have.

  • Important: remember to write the units when you write the equation

Using Scientific Measurements

• When writing down the value measured from a measuring instrument with lines, be sure to write down one extra place value to indicate accuracy.

• When writing down the value measured by an electronic device, do not round or add places, write what is exactly written on the screen.

• How to use values in scientific notation: use the “E“ button on the calculator

• When writing an answer the significant figures should consist of all the certain digits and one uncertain digit.

  • Certain digits are digits that we know for CERTAIN

  • Uncertain digits are the digits that we eyeball and estimate

  • If a quantity is exact with no uncertain digits, then it has INFINITE significant figures

• Accuracy VS. Precision

  • Accuracy- how close to the target the mark is

  • Precision- how close each mark is to each other

• Rules for Calculations with SigFigs

  • Addition/Subtraction: limit and round answer to the same place as the last sigfig in the least precise measurement

  • Multiplication/Division: limit and round answer to have as many total significant figures as the measurement with the last number of sigfigs

The Chemistry Laboratory

• Lab safety: uhhhh, literally anything dangerous in the chem lab… don’t do it.

• Common Lab equipment: There’s a paper for that…