Chemistry - Unit 2 Part B

Chain Calculations

meaning when you have (multiplication, division, addition, subtraction, exponents), use order of operations to “clean” the calculation up

• “cleaning” means to apply the rounding after doing a set of operations

Scientific Notation

• numbers that are used in the sciences can be extremely small or large

• this is how it can be written

• used as a convenience to represent these extreme numbers

• used as a necessity for showing certain number of sig figs.

Scientific vs Exponential

the decimal must be behind first non-zero number vs. the decimal being anywhere in the number

Calculations with Scientific Notation

multiplication:
multiply the quantities in front of the 10^, then apply rules for sig figs, add exponents, write back into sci notation

division, divide the quantities, apply rules, subtract top power to the bottom power (top - bottom)

addition/subtraction:

make the exponent power the same, by moving values left or right
- final sum/difference must have least number of places, then make back into sci notation.

Evaluating Measurements

to be able to check quantitatively the quality of your work

2 calculations:

1. experimental error

2. percentage error

Experimental Error - the absolute difference between the actual value vs your work

• must contain a unit

Percentage Error - (Experimental Error/Actual Value) x 100

• units cancel out

<25% is considered decent quality

<10% is considered “good” quality
<0% is considered “exceptional” quality
no error