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Chemistry (CP)

Module 1 · Text Lab Safety
Module 2 · Text The Scientific Method
Module 3 · Media Law Vs. Theory
Module 4 · Media Accuracy Vs. Precision
Module 5 · Text Sig-Figs and Scientific Notation You are here
Module 6 · Text Matter
Module 7 · Text Displacement
Module 8 · Text Density
Module 9 · Text SI Units
Module 10 · Media Dimensional Analysis
Module 11 · Media The Periodic Table
Module 12 · Text Isotopes
Module 13 · Text Nuclear Reactions
Module 14 · Text Nuclear Fission and Fusion
Module 15 · Text Chemical Vs. Nuclear Reaction
Module 16 · Text Electron Shells
Module 17 · Text Ions
Module 18 · Text Solubility and Conductivity
Module 19 · Media Types of Bonding
Module 20 · Text Chemical Formulas
Module 21 · Text Functional Groups
Module 22 · Text Electron Domains
Module 23 · Text Polarity
Module 24 · Text Chemical Equations
Module 25 · Text Physical Vs. Chemical Change
Module 26 · Text Types of Reactions
Module 27 · Text Moles
Module 28 · Text Solubility and Molarity
Module 29 · Media Miracle Moles
Module 30 · Text Acids and Bases
Module 31 · Media pH and pOH
Module 32 · Text Dilutions
Module 33 · Text Neutralization Reactions and Titrations
Module 34 · Text Mol Ratios
Module 35 · Media Stoichiometry
Module 36 · Text Endothermic and Exothermic Energy Transfer
Module 37 · Text Specific Heat
Module 38 · Media Heating and Cooling Curves and Phase Change
Module 39 · Text Gas Laws and Kinetic Molecular Frequency.

Close the course

Module 5 of 39 · Text

Sig-Figs and Scientific Notation

Enyx Jiang

Significant Figures

The significant figures in a measurement include all the digits that can be known precisely plus a last digit that must be estimated

Rules:

Every non-zero digit in a recorded measurement is significant
Zero Rules:
- Leading Zeros- zeros that precede all the non-zero digits; NEVER count as sig-figs
  - eg. 0.00832-- 3 sig-figs
  - eg. 0.23-- 2 sig-figs
- Captive Zeros- zeros between non-zero digits; are counted as sig-figs
  - eg. 7003-- 4 sig-figs
  - eg. 409.076-- 6 sig-figs
- Trailing Zeros- zeros at the right end of a number; only count as sig-figs when there is a decimal point
  - eg. 456200-- 4 sig-figs
  - eg. 50938.00-- 7 sig-figs
Exact Numbers
- Obtained by counting, not by measuring devices
- Can be assumed to have an unlimited amount of sig-figs
- Can come from definitions
  - eg. 1 in.=2.54 cm
Multiplying and Dividing sig-figs
- The answer must contain no more sig-figs than the measurement with the least sig=figs
- The position of the decimal point is irrelevant
  - eg. 5.89 x 4.5 = 27
Adding and Subtracting sig-figs
- The answer must contain the same number of sig-figs to the right of the decimal point as the measurement with the fewest sig-figs to the right of the decimal point
  - eg. 61.2 = 9.621 = 70.2

Scientific Notation

Chemists use scientific notation is used for very large or small numbers

eg. the mass of a hydrogen atom is 0.00000000000000000000000167 grams
eg. 2.0 grams of hydrogen is composed of 602000000000000000000000 hydrogen molecules

Numbers are written as the product of two numbers:

A coefficient
A power of 10 with an exponent
- The exponent tells you how many times you multiply a number by 10
- Numbers greater than 1 have a positive exponent (# of places the decimal moves left)
- Numbers less than 1 have a negative exponent (# of places the decimal moves right)
  - eg. The number 23000 is written in exponential form as 2.3 x 10^4
  - eg. 0.000051 is written in exponential form as 5.1 x 10^-5
- Numbers between 1 and 10 do not need scientific notation
  - eg. 9 = 9 x 10⁰
  - 1.2 = 1.2 x 10⁰
  - 7.562580 = 7.562580 x 10⁰
    - All have an exponent of zero (10⁰ = 1)