chapter2_ksjk


 * Section 2-1**

__The Scientific Method:__ //A logical approach to solving problems by…//
 * 1) Observing Facts
 * Qualitative properties
 * Nature, descriptive qualites: sky is blue
 * Quantitative properties
 * Measurements, numbers: S.I. System, Scientific Notation, Uncertainty, Dimensional Analysis
 * 1) Hypothesizing: //an educated guess//
 * 2) Experimenting
 * 3) Theororizing
 * The Big Bang Theory, Natural Selection
 * Model: //an// //explanation of how things occur//


 * Section 2-2**

__SI (system international) base units:__

Mass is NOT the same as weight
 * Mass – Kilogram (kg)
 * Length – Meter (m)
 * Time – Second (s)
 * Count – Mole (mol)
 * Temperature – Kelvin (K)

__SI derived units (combinations of base units):__


 * Area – square meter (m2)
 * Volume – cubic meter (m3)
 * Density – kg/m3
 * Force – Newton (N)
 * Pressure – Pascal (Pa)
 * Energy – Joule (J)
 * Power – Watt (W)
 * Voltage (V)
 * Frequency – Hertz (Hz)

__Conversions to know:__
 * 1 mol = 6.022 * 1023
 * 1 calorie = 4.184 Joules

Metric Prefixes:


 * Prefix || Abbreviation || Conversion || Sci Not ||
 * mega- || M || X 1,000,000 || 10^6 ||
 * kilo- || k || X 1,000 || 10^3 ||
 * deci- || d || X .1 || 10^(-1) ||
 * centi- || c || X .01 || 10^(-2) ||
 * milli- || m || X .001 || 10^(-3) ||
 * micro- || µ || X .000001 || 10^(-6) ||
 * nano- || n || X .000000001 || 10^(-9) ||

__Density:__ //the ratio of mass to volume//

__mass__ volume = density

Density Practice Problems:

1. The density of ethanol is .78 g/mL. Calculate the volume of 94.4 g of ethanol.

A. we have 94.4 g of ethanol B. we want its volume C. __94.4 g .__ .78 g/mL = 121 mL

2. Determine the density of a 21.232 g cylinder whose radius is 1.42 cm and whose height is 10 cm.

A. we have 21.232 g B. we want to first find the cylinder’s volume in order to find its density C. volume pi(1.42)2(10) = 63 cm D. density=__21.232 g__ 63 cm^3 = 0.34 g/cm^3

The Rules of __DIMENSIONAL ANALYSIS:__

1. Determine what you have. 2. Determine what you want. 3. Put what you have on top and what you want on bottom. 4. Always put the starting unit on the bottom of the next conversion. 5. ALWAYS use units.

Dimensional Analysis Conversion Practice Problems:

1. Convert 345 cm to miles.

A. we have 345 cm B. we want our answer in meters C. __345 cm__ __1 in__ __.__ __1 ft__ __1 mi .__ = .0020 mi 1 2.54 cm 12 in 5,280 ft

2. Convert 2 yrs to weeks.

A. we have 2 yrs B. we want our answer in wks C. __2 yrs__ __12 months__ __4 wks__ __7 days__ = 672 wks 1 1 yr 1 mnth 1 wk

3. Convert 54 mi/h into m/s (given: 1 km = 0.621 mi).

A. we have 54 mi/h B. we want our answer in m/s C. __54 mi__ __1 km__ __1000 m__ __1 hr__ __1 min__ 1 hr .621 mi 1 km 60 min 60 sec = 24 m/s (after determining # sig figs)


 * Section 2-3**

__Accuracy vs. Precision__

Accuracy - closeness of measurements to the //correct value// of quantity measured. Precision - repeated trials give the same answer; consistent; //in the same range// multiple times.

__Calculating Percentage Error

Experimental Value - Actual Value__ % error = Actual Value X 100

__SIGNFIANT FIGURE__: //a measurement that consists of all the digits you know with certainty plus 1 final digit, which is somewhat uncertain or is estimated.//

The rules of "Sig Figs":

1. All non-zero digits are significant (457.3 = 4) 2. Zeros appearing between nonzero digits are significant (707 =3) 3. Leading zeroes are NEVER sig figs (005=1) 4. Trailing zeroes are significant if a decimal is present (200=1, but 200. = 3) 5. Exact numbers have infinite sig figs 1 dozen = 12: //not open to interpretation// Any measurement: //open to interpretation//

Remember that...

When adding or subtracting decimals, the answer must have the same # of digits to the right of the decimal point as there are in the measurement having the fewest digits to the right of the decimal point.

For multiplication or division, the answer can have no more sig figs than there are in the measurement with the fewest number of sig figs.

__SCIENTIFIC NOTATION__

M x 10^n

M = A number __>__1<10 n = whole # found by counting the number of places to the decimal point

__Proportions__

Direct proportion: dividing one by the other gives a constant value y = kx

Inverse proportion: multiplying one by the other gives a constant value xy = k