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