Figure 01.091. Bell work: On your bell work page, please give

me a few sentences describing the differences

between mixtures and pure substances

2. Turn in Safety Poster, Matter Packet, and the PT scavenger hunt into

the box.

1. Solutions may be:

a) liquids or gases.b) liquids only.c) solids, liquids, or gases.d) none of the above.

2. Properties that describe the way a substance will react to form other substances are known as:

a) homogeneous properties.b) heterogeneous properties.c) chemical properties.d) physical properties.

3. When nitric acid is added to a test tube containing copper, nitrogen dioxide gas is formed. This is the result of:

a) an accident.b) an extensive property.c) a chemical reaction.d) a physical change.

1. Solutions may be:

solids, liquids, or gases.

2. Properties that describe the way a substance will react to form other substances are known as:

chemical properties.

3. When nitric acid is added to a test tube containing copper, nitrogen dioxide gas is formed. This is the result of:

a chemical reaction.

Method, Measurement, etc.

Modern Chemistry Chapter 2

Scientific Method

• Scientific Method- logical approach to solving problems by observing and collecting data, formulating hypotheses, testing them, and formulating theories based on data.

• System- specific portion of matter in a given region of space that has been selected for study (container holding experiment and all of its contents).

Scientific Method

1. Observing and collecting dataa) Using sensesb) Taking measurements

2. Formulating Hypothesesa) Hypothesis- testable statement based on

observations and datab) If, then statements

Scientific Method3. Testing Hypotheses

a) Experiments that include controls (constants) and variables (changes).

4. Theorizinga) Model- an explanation of how phenomena occur

and how data or events are related. i. Atomic Model

b) Theory- broad generalization that explains a body of facts

i. KMT; Collision theory

SI Unit Prefixes - Part I

Name Symbol Factor

tera- T 1012

giga- G 109

mega- M 106

kilo- k 103

hecto- h 102

deka- da 101

SI Unit Prefixes- Part II

Name Symbol Factor

deci- d 10-1

centi- c 10-2

milli- m 10-3

micro- μ 10-6

nano- n 10-9

pico- p 10-12

femto- f 10-15

The Seven Base SI UnitsQuantity Unit Symbol

Length meter m

Mass kilogram kg

Temperature kelvin K

Time second s

Amount of Substance

mole mol

Luminous Intensity candela cd

Electric Current ampere a

Derived SI Units (examples)Quantity unit Symbol

Volume cubic meter m3

Density kilograms per cubic meter

kg/m3

Speed meter per second m/s

Newton kg m/ s2 N

Energy Joule (kg m2/s2) J

Pressure Pascal (kg/(ms2) Pa

SI Unit Prefixes for LengthName Symbol

gigameter Gm 109

megameter Mm 106

kilometer km 103

decimeter dm 10-1

centimeter cm 10-2

millimeter mm 10-3

micrometer μm 10-6

nanometer nm 10-9

picometer pm 10-12

Measurement

• Measurement: a type of observation• Qualitative measurements: descriptive words

– Ex: hot, cold, heavy, light, big, blue, furry• Quantitative measurement: observation

made with a measuring instrument and includes both a number and a unit– Ex: ruler, balance, thermometer,

graduated cylinder, 13.5°C, 25kg, 17L

• Accuracy: How close a measurement is to the true or accepted value–Ex: Weighing a 50g mass50.00g – accurate32.18g – not accurate49.99g – accurate

• Precision: How close multiple measurements are to each other– Ex: Take the weight of a 50g mass

Accurate, precise: Accurate, precise:50.00g 50.00g50.00g 49.99g50.00g 50.00g

Not accurate, precise:32.18g32.18g32.18g

Example: Evaluate whether the following are precise, accurate or

both.

Example: Evaluate whether the following are precise, accurate or

both.

Accurate

Not Precise

Not Accurate

Precise

Accurate

Precise

An easy way to remember…

ACcurate = CorrectPRecision = Reproducibility

A student measured the concentration of a solution three times, obtaining values of 0.010 M, 0.060 M, and 0.030 M. The average concentration was thus 0.033 M. The accepted value was 0.034 M. The student’s data has:

a. good accuracy and good precision.b. poor accuracy but good precision.c. poor accuracy and poor precision.d. good accuracy but poor precision.

A student measured the concentration of a solution three times, obtaining values of 0.010 M, 0.060 M, and 0.030 M. The average concentration was thus 0.033 M. The accepted value was 0.034 M. The student’s data has:

a. good accuracy and good precision.b. poor accuracy but good precision.c. poor accuracy and poor precision.d. good accuracy but poor precision.

Percent Error

Percent Error

2. % Error= 1.60 – 1.00 X 100 = 60.0%1.00

Rules for Significant Figures

• Sig Figs are all of the digits known in measurement and one final which is estimated.

• All digits 1-9 are significant– Example: 129 – 3 sig figs

• Zeros between significant digits are always significant– Example: 5007 has 4 sig figs

Rules for Significant Figures

• Trailing zeros in a number are significant only if the number contains a decimal point– Example: 100.0 has 4 sig figs, 100 has 1 sig fig

• Zeros in the beginning of a number whose only function is to place the decimal point are not significant– Example: 0.0025 has 2 sig figs

• PACIFIC ATLANTIC RULE!

Calculations Using Sig Figs

• When multiplying and dividing, limit and round to the least number of sig figs in any of the factors.

– Example: 23.0cm X 432cm X 19cm = 190,000cm3

Calculations Using Sig Figs

• When adding and subtracting, limit and round your answer to the least number of decimal places in any of the numbers that make up your answer

– Example: 123.25cm + 46.0cm + 86.257cm = 255.5cm

How many significant figures are in the measured number 0.082060?

a. 3b. 4c. 5d. 6

How many significant figures are in the measured number 0.082060?

a. 3b. 4c. 5d. 6

6.03 grams + 7.1 grams = ?

a. 13 gramsb. 13.1 gramsc. 13.13 gramsd. 13.130 grams

6.03 grams + 7.1 grams = ?

a. 13 gramsb. 13.1 gramsc. 13.13 gramsd. 13.130 grams

6.03 grams / 7.1 milliliters = ?

a. 0.8 grams/milliliterb. 0.85 grams/milliliterc. 0.849 grams/milliliterd. 0.8492957 grams/milliliter

6.03 grams / 7.1 milliliters = ?

a. 0.8 grams/milliliterb. 0.85 grams/milliliterc. 0.849 grams/milliliterd. 0.8492957 grams/milliliter

Scientific Notation

• Short hand for writing very large or small numbers

• Two parts: Coefficient and Power of 10

A number between 1 and 10 (can include 1 but not 10).

Exponent: +

exponent - exponent

Scientific Notation Examples:

Write the following numbers in scientific notation:1. 41,0002. 0.00293. 60,007,0004. 0.000 000 1325. 123,000,000

4.1x1042.9x10-

3 6.0007x107

1.32x10-7

1.23x108

Calculator time!!

Try plugging these into your calculator. Put all answers in scientific notation.

*Instead of typing “x 10^,” use the “EE” or “EXP” button!*

37,000 x 7,0000.0008 x 0.0009(7x106) x (8x105)

2.59x108

7.2x1075.6x10

12

LecturePLUS Timberlake 40

Dimensional Analysis

1. A person has a height of 2.0 meters. What is

that height in inches?

Initial unit = m Final unit = _______

2) Blood has a density of 0.05 g/mL. If a person

lost 0.30 pints of blood at 18°C, how many ounces

of blood would that be?

Initial = pints Final unit = _______

LecturePLUS Timberlake 41

How many minutes are in 2.5 hours?

Initial unit 2.5 hr Conversion Final factor unit2.5 hr x 60 min = 150 min 1 hr

cancel Answer (2 SF)

LecturePLUS Timberlake 42

Your Turn

A rattlesnake is 2.44 m long. How long is the snake in cm?

1) 2440 cm2) 244 cm3) 24.4 cm

LecturePLUS Timberlake 43

Solution

A rattlesnake is 2.44 m long. How long is the snake in cm?

2.44 m x 100 cm = 244 cm 1 m

LecturePLUS Timberlake 44

One more…

How many seconds are in 1.4 days?

Unit plan: days hr min seconds

1.4 days x 24 hr x ?? 1 day

LecturePLUS Timberlake 45

Solution

Unit plan: days hr min seconds

2 SF Exact1.4 day x 24 hr x 60 min x 60 sec

1 day 1 hr 1 min

= 1.2 x 105 sec

LecturePLUS Timberlake 46

Unit Check

What is wrong with the following setup?

1.4 day x 1 day x 60 min x 60 sec 24 hr 1 hr 1 min

LecturePLUS Timberlake 47

Unit Check

1.4 day x 1 day x 60 min x 60 sec 24 hr 1 hr 1 min

Units = day2/hr2 Not the final unit needed

LecturePLUS Timberlake 48

Steps to Problem Solving

Read problem Identify data Write down a unit plan from the initial unit

to the desired unit Select conversion factors Change initial unit to desired unit Cancel units and check Do math on calculator Give an answer using significant figures