# scientific method starting on p. 29 scientific method – scientific method – system – system...

Embed Size (px)

TRANSCRIPT

Scientific Method Scientific Method starting on p. 29starting on p. 29

Scientific method –Scientific method – System –System – Hypothesis-Hypothesis- Testing hypothesis-Testing hypothesis- Model –Model – Theory-Theory- Stages in the Scientific MethodStages in the Scientific Method

Look at page 31

Stages in scientific method

Whoosh!

SYSTEM

SURROUNDINGS

Energy Released

C3H7OH + O2

CO2 + H2O

Po

ten

tial

En

erg

y

Analyze this graph and formulate a Hypothesis p. 30

Section 1 Scientific MethodChapter 2

Homework

Chapter 2 Section 1: P. 31 ( 1-5)

Qualitative Qualitative and and QuantitativeQuantitative

Qualitative – describes qualities, Qualitative – describes qualities, characteristics, textures, etc. Descriptions characteristics, textures, etc. Descriptions without numberswithout numbers

Quantitative – Describes quantities, mass, Quantitative – Describes quantities, mass, volume, length (numbers)volume, length (numbers)

Units of MeasurementUnits of Measurement

Quantity – what is being measured.Quantity – what is being measured.

example: volume, length, massexample: volume, length, mass

Unit – a standard of measurementUnit – a standard of measurement

example: liter, meter, kilogramexample: liter, meter, kilogram

Lesson 1: Lesson 1: LengthLength

T. Trimpe 2008 http://sciencespot.net/

English vs. Metric Units

Left Image: http://webapps.lsa.umich.edu/physics/demolab/controls/imagedemosm.aspx?picid=1167Right Image: http://share.lancealan.com/N800%20ruler.jpg

Which is longer?

A. 1 mile or 1 kilometer

B. 1 yard or 1 meter

C. 1 inch or 1 centimeter

1.6 kilometers

1 mile

1 yard = 0.9444 meters

1 inch = 2.54 centimeters

Metric Units

The basic unit of length in the metric system in the meter and is represented by a lowercase m.

Metric Units

1 Kilometer (km) = 1000 meters 1 Hectometer (hm) = 100 meters

1 Meter = 100 Centimeters (cm) 1 Dekameter (dam) =10 meters

1 Meter = 1000 Millimeters (mm) 1 Meter = 10 Decimeters (dm)

Which is larger?

A. 1 meter or 105 centimeters

B. 4 kilometers or 4400 meters

C. 12 centimeters or 102 millimeters

D. 1200 millimeters or 1 meter

Measuring Length

Ruler: http://www.k12math.com/math-concepts/measurement/ruler-cm.jpg

How many millimeters are in 1 centimeter?

What is the length of the line in centimeters? _______cm

What is the length of the line in millimeters? _______mm

What is the length of the line to the nearest centimeter? ________cm

HINT: Round to the nearest centimeter – no decimals.

1 centimeter = 10 millimeters

Lesson 2: Lesson 2: MassMass

T. Trimpe 2008 http://sciencespot.net/

English vs. Metric Units

Which is larger?

1. 1 Pound or 100 Grams

2. 1 Kilogram or 1 Pound

3. 1 Ounce or 1000 Milligrams

1 pound = 453.6 grams

100 kg = 220 pounds

1 ounce of gold = 28,349.5 milligrams

Metric Units

Mass refers to the amount of matter in an object.

The base unit of mass in the metric system is the kilogram and is represented by kg.

Metric Units

1 Kilogram (kg) = 1000 Grams (g) 1 Hectogram (hg) = 100 grams

1 Gram (g) = 1000 Milligrams (mg) 1 Dekagram (dag) =10 grams

1 Gram (g) = 100 Centigrams (cg) 1 Gram = 10 Decigrams (dg)

Which is larger?

A. 1 kilogram or 1500 grams

B. 1200 milligrams or 1 gram

C. 12 milligrams or 12 kilograms

D. 4 kilograms or 4500 grams

Kilogram Prototype Image - http://en.wikipedia.org/wiki/Kilogram

Measuring Mass

Top Image: http://www.southwestscales.com/Ohaus_Triple_Beam_750-SO.jpgBottom Image: http://www.regentsprep.org/Regents/biology/units/laboratory/graphics/triplebeambalance.jpg

We will be using triple-beam balances to find the mass of various objects.

The objects are placed on the scale and then you move the weights on the beams until you get the lines on the right-side of the scale to match up.

Once you have balanced the scale, you add up the amounts on each beam to find the total mass.

What would be the mass of the object measured in the picture?

_______ + ______ + _______ = ________ g

Lesson 3: Lesson 3: VolumeVolume

T. Trimpe 2008 http://sciencespot.net/

English vs. Metric Units

Which is larger?

A. 1 liter or 1 gallon

B. 1 liter or 1 quart

C. 1 milliliter or 1 fluid ounce

1 gallon = 3.79 liters

It would take approximately 3 ¾ 1-liter bottles to equal a gallon.

1 fl oz = 29.573 ml

1 12-oz can of soda would equal

approximately 355 ml.

1 quart = 0.946 liters

Metric Units

Volume is the amount of space an object takes up.

The base unit of volume in the metric system is the liter and is represented by L.

Metric Units

1 liter (L) = 1000 milliliters (mL)

1 milliliter (mL) = 1 cm3

1 Kiloliter (kL) = 1000 Liters (L) 1 Hectoliters (hL) = 100 Liters

1 Dekaliter (daL) =10 Liters 1 Liter (L) = 100 Centiliters (cL) 1 Liter (L) = 10 Deciliters (dL)Which is larger?

A. 1 liter or 1500 milliliters

B. 200 milliliters or 1.2 liters

C. 12 cm3 or 1.2 millilitersLiter Image: http://www.dmturner.org/Teacher/Pictures/liter.gif

Measuring Volume

Top Image: http://www.tea.state.tx.us/student.assessment/resources/online/2006/grade8/science/images/20graphicaa.gifBottom Image: http://morrisonlabs.com/meniscus.htm

We will be using graduated cylinders to find the volume of liquids and other objects.

Read the measurement based on the bottom of the meniscus or curve. When using a real cylinder, make sure you are eye-level with the level of the water.

What is the volume of water in the cylinder? _____mL

What causes the meniscus?

A concave meniscus occurs when the molecules of the liquid attract those of the container. The glass attracts the water on the sides.

Measuring Liquid Volume

Imag

es c

reat

ed a

t ht

tp:/

/ww

w.s

tand

ards

.dfe

s.go

v.uk

/prim

aryf

ram

ewor

k/do

wnl

oads

/SW

F/m

easu

ring_

cylin

der.

swfWhat is the volume of water in each cylinder?

Pay attention to the scales for each cylinder.

Measuring Solid Volume

Click here for an online activity about volume. Choose Lessons Volume & Displacement

10 cm

9 cm

8 cm

We can measure the volume of regular object using the formula length x width x height.

_____ X _____ X _____ = _____

http

://re

sour

ces.

edb.

gov.

hk/~

s1sc

i/R_S

1Sci

ence

/sp/

en/s

ylla

bus/

unit1

4/ne

w/te

stin

gmai

n1.h

tm

We can measure the volume of irregular object using water displacement.

Amount of H2O with object = ______

About of H2O without object = ______

Difference = Volume = ______

Converting UnitsConverting Units

Conversion Factor – equal ratio that enables Conversion Factor – equal ratio that enables you to change one unit to anotheryou to change one unit to another

Example:Example:

1kg = 1000 g1kg = 1000 g

1kg1kg 1000g1000g

1000g or 1000g or 1 kg1 kg

Practice

1. ____g = 57.8 mg

2. _____km = 125m

3. ____mL = 0.65L

4. ____cg = 5.7mg

5. ____L = 286 mL

6. ____m = 112 cm

7. ___mg = 9.7 cg

8. ___ kg = 21 mg

9. __ mm = 0.003km

SOLVE

___ g = 125mg + 0.15kg +95cg+2g

2 g .95 g

150 g .125g

153.075g

Solve

1. ___g=125mg + .15kg + 95cg + 2g

2. ___cm=.13km + 29mm + 113cm + 1.5m

3. ___g=2835mg + 245cg + 3g + .23kg

Memorize!

1 L = 1000ml = 1000cm3

1mL = 1cm3

And all other conversions on green sheet

Sample Problem A – pg. 14Sample Problem A – pg. 14

Convert 0.851L to mlConvert 0.851L to ml

Sample problemsSample problems

Convert 253 ml to litersConvert 253 ml to liters

Answer:Answer:

Sample ProblemSample Problem

Convert 1258 cm to mConvert 1258 cm to m

Answer: Answer:

Sample ProblemSample Problem

Convert 15 g to kgConvert 15 g to kg

Answer: Answer:

Sample ProblemSample Problem

Convert 5.25 hours to secondsConvert 5.25 hours to seconds

Answer: Answer:

DensityDensity

A physical property.A physical property. Density equals the mass of an object Density equals the mass of an object

divided by its volume.divided by its volume. D =m/VD =m/V Units you will see: Units you will see: kg/m3 or g/ml or g/cmg/ml or g/cm3 3

Density can be used to identify substances.Density can be used to identify substances.

Derived SI Units p. 36

Quantity Quantity Symbol

Unit Unit Abbreviation

Area A Square meter

m2

Volume V Cubic meter

m3

Density D Kilogram per cubic

meter

kg

m3

SI Base Units p. 34

Density Practice

What is the density of a block of marble that occupies 310cm3 and has a mass of 853 grams?

Density Practice

A diamond has a density of 3.26 g/cm3. What is the mass of a diamond that has a volume of 0.35 cm3?

Density Practice

What is the volume of a sample of liquid mercury that has a mass of 76.2g, given that the density of mercury is 13.6 g/ml ?

Now…

Density Worksheet 1 & 2

Homework: Quiz over p. 42 (1-5) – next class

Uncertainty in MeasurementUncertainty in Measurement

A digit that must be A digit that must be estimated is called estimated is called

uncertain. A uncertain. A measurement always has measurement always has

some degree of some degree of uncertaintyuncertainty

Why Is there Uncertainty?Why Is there Uncertainty?

Measurements are performed with Measurements are performed with instruments instruments

No instrument can read to an infinite No instrument can read to an infinite number of decimal placesnumber of decimal places

Which of these balances has the Which of these balances has the greatest uncertainty in greatest uncertainty in

measurement?measurement?

Accuracy vs. PrecisionAccuracy vs. Precision Accuracy Accuracy - how close a measurement is - how close a measurement is

to the accepted valueto the accepted value

PrecisionPrecision - how close a series of - how close a series of measurements are to each othermeasurements are to each other

ACCURATE = CORRECT

PRECISE = CONSISTENT

Experimental DataExperimental Data

Carbon = 12.0107 amuCarbon = 12.0107 amu

During your experiment, you obtained the During your experiment, you obtained the following values: 12.0304, 12.0305, 12.0303following values: 12.0304, 12.0305, 12.0303

Are these Precise or Accurate?Are these Precise or Accurate?

Percent ErrorPercent Error

Indicates accuracy of a measurementIndicates accuracy of a measurement

% error = % error = Accepted – ExperimentalAccepted – Experimental x 100 x 100AcceptedAccepted

Percent ErrorPercent Error A student determines the density of a A student determines the density of a

substance to be 1.40 g/mL. Find the % substance to be 1.40 g/mL. Find the % error if the accepted value of the density error if the accepted value of the density is 1.36 g/mL.is 1.36 g/mL.

% error = % error = 1.36 – 1.401.36 – 1.40 x 100= x 100= 1.36 1.36

% error = - 2.9 %

Significant FiguresSignificant Figures

Indicate precision of a measurement.Indicate precision of a measurement.

Recording Sig FigsRecording Sig Figs– Sig figs in a measurement include the known Sig figs in a measurement include the known

digits plus a final estimated digitdigits plus a final estimated digit

2.35 cm

Rules for Counting Significant Rules for Counting Significant Figures - DetailsFigures - Details

Nonzero integersNonzero integers always count as always count as significant figures. significant figures.

3456 has 3456 has 4 sig figs.4 sig figs.

Rules for Counting Significant Rules for Counting Significant Figures - Details Figures - Details

Zeros Zeros -Beginning zeros do not count as -Beginning zeros do not count as

significant figures.significant figures. 0.0486 has 0.0486 has 3 sig figs3 sig figs

Rules for Counting Significant Rules for Counting Significant Figures - Details Figures - Details

Zeros Zeros - Middle zeros always count as - Middle zeros always count as

significant figures.significant figures. 16.07 has 16.07 has 4 sig figs.4 sig figs.

Rules for Counting Significant Rules for Counting Significant Figures - Details Figures - Details

Zeros Zeros End zeros are significant only if End zeros are significant only if

the number contains a decimal the number contains a decimal point. point.

9.300 has 9.300 has 4 sig figs.4 sig figs.

4. 0.0804. 0.080

3. 5,2803. 5,280

2. 4022. 402

1. 23.501. 23.50

Significant FiguresSignificant Figures

Counting Sig Fig Examples

1.1. 23.50 23.50

2.2. 402 402

3.3. 5,28 5,2800

4. 0.04. 0.08080

____ sig figs____ sig figs

___ sig figs___ sig figs

____ sig figs____ sig figs

____ sig figs____ sig figs

Sig Fig Practice #1 Sig Fig Practice #1

How many significant figures in each of the following?How many significant figures in each of the following? 1.0070 m 1.0070 m

5 sig figs5 sig figs 17.10 kg 17.10 kg

4 sig figs4 sig figs 100 890 L 100 890 L

5 sig figs5 sig figs 3.29 x 103.29 x 1033 s s

3 sig figs3 sig figs 0.0054 cm 0.0054 cm

2 sig figs2 sig figs 3 200 000 3 200 000

2 sig figs2 sig figs

Significant FiguresSignificant Figures

Calculating with Sig FigsCalculating with Sig Figs– Multiply/DivideMultiply/Divide - The # with the fewest sig figs - The # with the fewest sig figs

determines the # of sig figs in the answer.determines the # of sig figs in the answer.

(13.91g/cm3)(23.3cm3) = 324.103g

324 g

4 SF 3 SF3 SF

Rules for Significant Figures in Rules for Significant Figures in Mathematical Operations Mathematical Operations

6.38 x 2.0 = 6.38 x 2.0 = 12.76 12.76 13 (2 sig figs) 13 (2 sig figs)

Sig Fig Practice #2 Sig Fig Practice #2

Calculation Calculator says: AnswerCalculation Calculator says: Answer 3.24 m x 7.0 m ____ m3.24 m x 7.0 m ____ m22 __ m __ m22

100.0g ÷ 23.7cm100.0g ÷ 23.7cm3 ________3 ________ g/cm g/cm33 ____g/cm ____g/cm33

0.02cm x 2.371cm ______ cm0.02cm x 2.371cm ______ cm22 ____ cm ____ cm22

710 m ÷ 3.0 s ________ m/s ____ m/s710 m ÷ 3.0 s ________ m/s ____ m/s

Significant FiguresSignificant Figures

Calculating with Sig Figs (con’t)Calculating with Sig Figs (con’t)– Add/SubtractAdd/Subtract - The # with the lowest decimal - The # with the lowest decimal

value determines the place of the last sig fig in value determines the place of the last sig fig in the answer.the answer.

3.75 mL

+ 4.1 mL

7.85 mL 7.9 mL

3.75 mL

+ 4.1 mL

7.85 mL

Significant FiguresSignificant Figures Calculating with Sig Figs (con’t)Calculating with Sig Figs (con’t)

– Exact NumbersExact Numbers do not limit the # of sig figs in the do not limit the # of sig figs in the answer.answer. Counting numbers: 12 studentsCounting numbers: 12 students

Exact conversions: 1 m = 100 cmExact conversions: 1 m = 100 cm

““1” in any conversion: 1 in = 2.54 cm1” in any conversion: 1 in = 2.54 cm

Significant FiguresSignificant Figures

5. (15.30 g) ÷ (6.4 mL)5. (15.30 g) ÷ (6.4 mL)

Practice Problems

= 2.390625 g/mL= 2.390625 g/mL

18.1 g18.1 g

6. 18.9 g

- 0.84 g18.06 g

4 SF 2 SF

2.4 g/mL2.4 g/mL2 SF

Scientific NotationScientific Notation

In science, we deal with some very In science, we deal with some very LARGELARGE numbers: numbers:

1 mole = 6020000000000000000000001 mole = 602000000000000000000000 In science, we deal with some very In science, we deal with some very

SMALLSMALL numbers: numbers: Mass of an electron = Mass of an electron = 0.000000000000000000000000000000091 kg0.000000000000000000000000000000091 kg

Imagine the difficulty of Imagine the difficulty of calculating the mass of 1 mole of calculating the mass of 1 mole of

electrons!electrons!

0.000000000000000000000000000000091 kg 0.000000000000000000000000000000091 kg x 602000000000000000000000x 602000000000000000000000 ????????????????????????????????????????????????????????????????????

Scientific Notation:Scientific Notation:

A method of representing very large or A method of representing very large or very small numbers in the form: very small numbers in the form:

M x 10M x 10nn

M is a number between 1 and 9.9M is a number between 1 and 9.9 n is an integern is an integer

2 500 000 000

Step #1: Insert an understood decimal pointStep #1: Insert an understood decimal point

.

Step #2: Decide where the decimal Step #2: Decide where the decimal must end must end up so that one number is to its up so that one number is to its leftleftStep #3: Count how many places you Step #3: Count how many places you bounce bounce the decimal pointthe decimal point

123456789

Step #4: Re-write in the form M x 10Step #4: Re-write in the form M x 10nn

2.5 x 102.5 x 1099

The exponent is the number of places we moved the decimal.

0.00005790.0000579

Step #2: Decide where the decimal Step #2: Decide where the decimal must end must end up so that one number is to its up so that one number is to its leftleftStep #3: Count how many places you Step #3: Count how many places you bounce bounce the decimal pointthe decimal pointStep #4: Re-write in the form M x 10Step #4: Re-write in the form M x 10nn

1 2 3 4 5

5.79 x 105.79 x 10-5-5

The exponent is negative because the number we started with was less than 1.

PERFORMING PERFORMING CALCULATIONS IN CALCULATIONS IN SCIENTIFIC NOTATIONSCIENTIFIC NOTATION

Scientific NotationScientific Notation

7. 7. 2,400,000 2,400,000 gg

8. 8. 0.00256 kg0.00256 kg

9.9. 7 7 10 10-5-5 km km

10.10. 6.2 6.2 10 1044 mm mm

Practice Problems

________________gg

________ kg________ kg

________ km________ km

_______ mm_______ mm

Scientific NotationScientific Notation

Calculating with Sci. NotationCalculating with Sci. Notation

(5.44 × 10(5.44 × 1077 g) ÷ (8.1 × 10 g) ÷ (8.1 × 1044 mol) = mol) =

5.44EXPEXP

EEEE÷÷

EXPEXP

EEEE ENTERENTER

EXEEXE7 8.1 4

= 671.6049383 = 670 g/mol = 6.7 × 102 g/mol

Type on your calculator:

Direct Proportions Direct Proportions

The The quotientquotient of two variables is a of two variables is a constant constant

As the value of one variable increases, As the value of one variable increases, the other must also increase the other must also increase

As the value of one variable decreases, As the value of one variable decreases, the other must also decrease the other must also decrease

The graph of a direct proportion is a The graph of a direct proportion is a straight linestraight line

Inverse Proportions Inverse Proportions

The The productproduct of two variables is a of two variables is a constant constant

As the value of one variable increases, As the value of one variable increases, the other must decrease the other must decrease

As the value of one variable decreases, As the value of one variable decreases, the other must increase the other must increase

The graph of an inverse proportion is a The graph of an inverse proportion is a hyperbolahyperbola

ProportionsProportions

Direct ProportionDirect Proportion

Inverse ProportionInverse Proportion

xy

xy

1

y

x

y

x