1. Ch. 3 Scientific Measurement

2. 3.1 Using & expressing measurements
Scientific notation
Coefficient is greater than 1 but less than 10
Multiplied by a power of 10
Each decimal place change = a power of ten
Handout with more info on my website

3. Into scientific notation
Move decimal to R, (-) power
Move decimal to L, (+) power
Ex: x 104
x 10-7
Out of scientific notation
Do opposite as above
(+) power, move decimal to R
(-) power, move decimal to L

4. Multiplication & division See sample problem Addition & subtraction
Ex: x 105 => 255,000
9.18 x =>
Multiplication & division
See sample problem
Addition & subtraction

5. Accuracy, precision, & error
Accuracy – how close a measurement comes to actual or true value
Precision – how close a series of measurements are to one another
You can be accurate & precise OR not accurate & yet precise OR not accurate & not precise

6. Accepted value: correct value
Experimental value: measured in lab
Error is the difference
Error = Exp. value – Acc. value
%Error = Error X 100%
Acc value

7. Significant figures Determining sig figs in measurements – see p. 67
Sig figs in calculations
Rounding – p. 69
Addition & subtraction – p. 70
Multiplication & division – p. 71
Go thru sample probs

8. 3.2 Units of Measurement Using SI units
Based on multiples of ten (decimals – NO fractions!)
SI base units – p. 74
Derived units – by way of a calc. (cm3)
nonSI units sometimes used for practicality (ex: atm; mmHg)
Prefixes used to indicate size or quantity of “stuff” making up measurement (p. 75)

9. Units of length (p. 75) Units of volume (p. 76) Basic unit: meter (m)
Use unit to best make measurement (length of river: km)
Units of volume (p. 76)
Basic unit: m3
nonSI unit: Liter (L) (1 L = 1 dm3)
Can be measured directly (graduated cylinder) OR calculated (from L x W x H)

10. Units of mass (p. 77)
Basic unit is kilogram (kg) – only base unit with a prefix
Quantity of matter in object – does not change
Measured with a balance
Weight is NOT the same as mass
A measure of gravitational force on object in units of newtons (N); uses a scale
Can change due to amt of gravity on object

11. Temperature scales Units of energy nonSI – calorie (cal)
SI – joule (J)
1 cal = J OR 1 J = cal
1 Cal = 1000 cal (how food calories are measured)
Temperature scales
A measure of hot or cold object is; based on avg kinetic energy of particles within object

12. Celsius (oC)
What is used to make measurements
Kelvin (K)
Used for many calculations
Converted from Celsius
Aka absolute scale (all molecular motion stops at 0 K, or absolute zero)
Conversions
K = oC + 273
oC = K - 273
Water: BP = 100oC & 373 K
FP = 0 oC & 273 K

13. Density Mass per unit volume Derived unit Intensive physical property
Common densities p. 81
Units for solids & liquids: g/cm3
(nonSI for liquids: g/mL)
Units for gases: g/dm3
(nonSI unit: g/L most often used)

14. 3.3 Solving Conversion Problems
Conversion factors
Made of 2 equal values as a fraction equal to 1
Changes numerical value but not quantity
Ex: 1 m = 100 cm - set up to cancel what to get rid of to leave unit you want

15. Dimensional analysis Ex: 1 m OR 100 cm 100 cm 1 m
Using conversion factors to change a units of a quantity
Analyze (list facts & unknown)
Calculate (set up conv factors to solve for unknown )
Evaluate (does result make sense?)
See sample problems

16. Simple unit conversions
In setting up conversion factor, unknown unit is in numerator & known unit is in denominator
See sample problem p. 88
Multistep problems
Uses several conversion factors
Think about sequence of factors from known to unknown
Take it one factor at a time
Cancel units. If last unit is NOT correct for answer, go back & check factor set-ups. Once correct, do math.