Post on 31-Dec-2015
Scientific method
Method for answering questions• Make an observation • Ask a question (hypothesis)• Obtain facts (experiment)• Explain experiment (conclusion)• Theory or law
Measurements – SI units
Quantity Name Unit
Length Meter M
Mass Kilogram(gram)
Kg(g)
Time Second S (sec)
Temperature Kelvin K
Amount Mole Mole
Metric prefixes
Prefix Abbrev factor
Kilo K 103
Deci d 10-1 (1/10)
Centi c 10-2 (1/100)
Milli m 10-3 (1/1000)
Micro 10-6 (1/1,000,000)
Nano n 10-9 (1/1,000,000,000)
Significant digits The certain and 1 estimated digit of
a measurement
Atlantic-Pacific ruleif a decimal is Absent, count
first non-zero number from Atlantic side
if a decimal is Present, count first non-zero number from the Pacific side
Practice
How many significant figures in each?
1. .00987 2. 987003. 987.004. 987009875. 987.00987
3
3
5
8
8
Calculations
Addition/subtractioncount least places after the
decimal
Multiplication/division
count the least number of significant digit
Practice Calculations
1. 2.3 x 11.0090=2. 15.00 =
3.73. 11 + 2.34 + 900.0560=4. (3.2 x 103)(6.003 x 10-2)=5. 8.90 x 106 = 5.1 x 10 -9
Problem Solving
1. Write known and unknown 2. Write equation 3. Use factor label method (start with
the units of the known) 4. Calculate 5. Circle answer with correct
significant figures
Ratios of equal terms
• 1 m = 10 dm1m 10 dm
10 dm 1m
• 1 min = 60 sec1 min 60 sec60 sec 1 min
For more see agenda p R-10
Factor label=Dimensional AnalysisUsing units to solve problems
Show work using units
1. How many seconds in 14 days? Show work.
2. How many mL in 1.09 kL?3. Convert 3.4 g/ml to dg/cL
Computer Graphing
Excel A- x axis,flask size (ml) B- Y axis, time (sec) Highlight all 2columns Chart Wizard X,Y scatter middle chart, left column Title (include your name), label both axis New sheet Unshade background Print 1 to science dept
Excel
A- x axis (volume), B- Y axis (mass) Highlight all 2columns, Chart Wizard X,Y scatter top chart, left column Title (include your name), label both axis New sheet Chart
add trend line Linear
options tab Check off intercept=0 display equation chart,
Unshade background/format plot area/white box Print to lexchex or sci dept
Slope
Rise = y2-y1 = m2-m1 = mass
Run x2-x1 v2-v1 volume
Pick 2 points on the line. Write the coordinates (x1,y1)(x2,y2)
Calculate the density
Do this on your graph.
Pure Matter
Elementscannot be broken down by chemical processes
CompoundChemical combination of elements(share or transfer of electrons)
MatterAnything that has mass and volume
do not copy in notebook Density Pressure
ContainerSolid High not affected own
shape
Liquid High not affected takes shape
Gas low affected fills
Plasma low affected fills
Changes in Matter
Physical changes Involve no change in composition Physical properties:
Boiling/melting point, density, color, odor, ductile
Chemical changes Involves a change in composition
Heat changeColor changeGas evolvedPrecipitate formed
Chemical properties:
combustion, reactivity
Changes of State
What is happening to the molecules as ice heats up? Change from one state to another takes energy
Is the melting point and freezing point the same? Heat of fusion Is the evaporation and condensation pt the same? Heat of evaporation What is the difference between steamed and
boiled?
Cooling Curve
50
100
150
200
250
Tem
p (
Degre
es C
)
0 50 100 150 200 250 Time (seconds)
Temperature versus Time
Liquid
Solid
GasCondense/evaporate
Freeze/melt
Temperature Scales Fahrenheit was a thermometer maker
• He was a very good thermometer maker• Why do we still use his scale?
Celsius is based on the melting point and boiling point of water• 0o C = Freezing point of Swiss Alps snow• 100o C = Boiling point at sea level
Why does it have to be at sea level?• Why is this better than Fahrenheit?