Thursday, October 31, 2013
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Transcript of Thursday, October 31, 2013
Thursday, October 31, 2013 Happy Halloween! Standard IE1: Scientific progress is made by asking meaningful questions and conducting careful scientific experiments.
Independent Practice: Section 3.3 Reading Packet
Question: Copy the chart into your Journal.
Quantity SI Base Unit
Symbol
Length Meter m
Mass Kilogram kg
Temp Kelvin K
Time Second s
Amount of Substance
Mole mol
Luminous Intensity
Candela cd
Electric Current
Ampere A
Measurements and Calculations
Units of Measurement Measurements involve NUMBER and UNIT
Represent a quantity: has magnitude, size, or amount
Gram = unit of measurement Mass = quantity
Units of Measurement Scientists around the world agree on one system… International System of Units (le Systeme International d’Unites)
SI units Built from seven base units
SI Base Units
Units of Measurement
Units of Measurement Metric Prefixes – make units easier to use
Make the unit smaller or larger Unit = prefix + base unit Table pg. 74
Mass Measures quantity of matter SI unit: kilogram, kg ______ kg = _____ g gram used for smaller masses Weight: measure of gravitational pull
Length SI unit: meter, m Longer distances: kilometer, km _______ km = _______ m Shorter distances: centimeter, cm _______ m = ________ cm
Volume SI unit: m3
A derived unit: combination of base units by multiplying or dividing
SI unit for Area: l x w = m x m = m2
Volume: l x w x h = m x m x m = m3
Also: liters (L), mL, dm3 and cm3
1 L = 1 dm3 = 1000mL = 1000 cm3
Derived Units
Scientific Notation Put the numbers in the form
a x 10n
a has one # to left of decimal If # is bigger than 1 + exponent If # is less than 1 - exponent
Scientific Notation Review: Write in scientific notation or standard notation. a. 32,700b. 0.0003412c. 3.901 x 10-6
d. 4.755 x 108
Let’s PracticeScientific Notation Worksheet
Significant Figures (Sig Figs) How many numbers mean anything? When we measure, we can (and do) always estimate between the smallest marks.
21 3 4 5
Significant Figures (Sig Figs)Better marks better estimate.Last number measured actually an estimate
21 3 4 5
Rules for Significant Figures
1) All nonzero digits are significant.• 457 cm has 3 sig figs• 2.5 g has 2 sig figs
2) Zeros between nonzero digits are significant.• 1007 kg has 4 sig figs• 1.033 g has 4 sig figs
3) Zeros to the left of the first nonzero digit are not significant. They are not actually measured, but are place holders.• 0.0022 g has 2 sig figs• 0.0000022 kg has 2 sig fig
4) Zeros at the end of a number and to the right of a decimal are significant. They are assumed to be measured numbers.• 0.002200 g has 4 sig figs• 0.20 has 2 sig figs• 7.000 has 4 sig figs
5) When a number ends in zero but contains no decimal place, the zeros may or may not be significant. We use scientific (aka exponential) notation to specify.• 7000 kg may have 1, 2, 3 or 4 sig figs!
Sig Figs What is the smallest mark on the ruler that measures 142.15 cm?
142 cm? 140 cm? Does the zero mean anything? (Is it significant?)
They needed a set of rules to decide which zeroes count.
Sig Figs.
405.0 g 4050 g 0.450 g 4050.05 g 0.0500060 g
Sig Figs
Only measurements have sig figs. Counted numbers are exact – infinite sig figs
A dozen is exactly 12 Conversion factors: 100 cm = 1 m
Problems
50 has only 1 significant figure if it really has two, how can I write it?
Scientific notation
5.0 x 101 2 sig figs
Scientific Notation shows ALL sig figs
Rounding Rules
Round 454.62 to four sig figs to three sig figs to two sig figs to one sig fig
Sig Figs
How many sig figs in the following measurements?
458 g4085 g4850 g0.0485 g0.004085 g40.004085 g
Let’s PracticeSignificant Figures Worksheet
Journal - Wednesday, November 6, 2013 Standard IE1: Scientific progress is made by asking meaningful questions and conducting careful scientific experiments.
Independent Practice: Significant Figures Worksheet (#2)
Question: Copy the chart into your Journal. (next slide)
Prefix Meaning Factor
Mega (M) 1 million times larger than unit
106
Kilo (k) 1,000 times larger than unit
103
Deci (d) 10 times smaller than unit
10-1
Centi (c) 100 times smaller than unit
10-2
Milli (m) 1,000 times smaller than unit
10-3
Micro (μ) 1 million times smaller than unit
10-6
Nano (n) 1,000 million times smaller than unit
10-9
Pico (p) 1 trillion times smaller than unit
10-12
OPEN NOTE Quiz!! When?
Blocks 1 and 3: Wednesday, November 13, 2013
Blocks 2 and 4: Thursday, November 14, 2013
Topics Included: SI Units Scientific Notation
Significant Figures
Significant Figures in Calculations
Density Conversions
Vocabulary Review Calibration: a set of graduations to indicate values or positions.
Precision: Describes the closeness, or reproducibility, of a set of measurements taken under the same conditions.
Convey: To make something known to someone.
Significant: Very important.
Intervals: A period of time between events.
Review:Scientific Notationand Significant Figures Worksheets
Calculations with Significant Figures RulesAnnotate the Reading
Calculations with Sig Figs1. 165.86 g + 4.091g - 140 g +
27.32 g 2. (35.6 L + 2.4 L) / 4.083 = 3. 2.524 x (16.408 m – 3.88 m) =
Answers: 57g 9.31 L 31.62 m
Let’s PracticeSignificant Figures in Calculations WS
DensityDensity = mass D = m
volume VUnits: g/cm3 or g/mL but SI unit is kg/m3
derived unitUsed to identify substancesVaries with temperatureAs temp. increases density…
Density
Density Examples If a metal block has a mass of 65.0 grams and a volume of 22 cubic centimeters, what is the density of the block?
D = m V
D = 65.0 g = 3.0 g/cm3 22 cm3
Density Examples Aluminum has a density of 2.7 g/cm3. What volume of aluminum has a mass of 60 grams?
D = M V
20 cm3
Density Examples Gold has a density of 19.3 g/cm3. A block of metal has a mass of 80 g and a volume of 12 cm3. Could this block be a piece of gold?
No, because this block has a density of 7 g/cm3s
Unit Conversions
Unit Conversions Given information in one unit
need to find the equivalent in another unit
1. Identify what’s given2. Organize plan of attack3. Carry out plan WITH UNITS!!
Conversion factors
“A ratio of equivalent measurements.”
Start with two things that are the same.1 m = 100 cm
Can divide by each side to come up with two ways of writing the number 1.
Conversion factorsConversion factors
=
Conversion factorsConversion factors
11 m =100 cm
Conversion factorsConversion factors
11 m =100 cm
Conversion factorsConversion factors
11 m =100 cm
100 cm=1 m
1
Conversion Factors Unique way of writing the number 1.
Does NOT change the VALUE, it changes the UNITS.
Write the conversion factors for the following kilograms to grams
feet to inches 1 L = 1 dm3 = 1000mL = 1000 cm3
Let’s See How They Work
We can multiply by a conversion factor creatively to change the units .
13 inches is how many yards?
Let’s Try Some! 323 mm = _____ nm 3.2 miles = _____ in 250 gallons = _____ mL 15 days = _______ min
More Unit Conversions
More Involved
Derived Unit Conversions 54.3 cm3 = ______ m3
7.54 ft2 = _______ in2
Derived Unit Conversions 125.3 m/s = ______ mi/hr
625 g/mL = ______ kg/m3
100 km/hr = ______ mi/hr
Let’s PracticeDimensional Analysis
Where do these measurements come from?
Recording Measurements
Making Good Measurements We can do 2 things:1. Repeat measurement many times
- reliable measurements get the same number over and over- this is PRECISE
Making Good Measurements2. Test our measurement against a “standard”, or accepted value- measurement close to accepted value is ACCURATE
Video - 46
Measurements are Uncertain1. Measuring instruments are never
perfect2. Skill of measurer3. Measuring conditions4. Measuring always involves estimation
Flickering # on balance Between marks on instrument
Estimating Measurements
Error Probably not EXACTLY 6.35 cm Within .01 cm of actual value. 6.35 cm ± .01 cm 6.34 cm to 6.36 cm
Calculating Percent Error
Compares your measurement to accepted value
Negative if measurement is small Positive if measurement is big
experimental accepted
accepted
Value -ValuePercentage error = × 100
Value
Calculating Percent Error What is the % error for a mass measurement of 17.7g, given that the correct value is 21.2g?
Let’s PracticePercent Error Worksheet