unit 1: foundations of chemistry chapters 1, 2, & 3 chemistry 1l cy-creek high school

Unit 1: Foundations of Chemistry

Chapters 1, 2, & 3

Chemistry 1L

Cy-Creek High School

Scientific Processa.k.a. Scientific Method

Why do we need it?

What is the Scientific Process?

A systematic approach to problem solving Generally Composed of the following parts:

– Observations– Hypothesis– Experiment– Conclusion

Observations

Qualitative (Quality)- characterized as data you use your senses to describe– Ex: color, texture, emotion, taste, smell, etc.

Quantitative (Quantity, #)- something that can be measured– Ex: 212°F, 3 m, 1.0 L

What is an Inference?

How we interpret the observation

Scientific Process

Joe baked a cake for his mother’s birthday. When the cake was taken from the oven Joe noticed that the cake had not risen. Joe guessed that the oven had not heated to the right temperature. He set up this experiment to test his idea.

First, Joe put a thermometer in the oven. He then turned the oven dial to 350°F. He noticed that the preheating light came on when he turned the oven on. He waited until the preheating light went out. The light’s going out indicated that the oven was up to temperature. Joe then read the thermometer within the oven. It read 350°F. Joe concluded that the oven was working correctly.

Inference or Observation?

Joe thought the cake recipe was good. The preheating light came on when the

oven was turned on. The thermometer read 350°F. The cake did not rise.

Now What?

Classification – group similar observations together into categories

Hypothesis - Educated guess

Models – shows information about another object or event

Experiment Time!

Test your hypothesis

How? Controlled experiment – control group

(benchmark or comparison) and one or more changing variables

The Conclusion (not quite yet)

Analyze your data Look back at your hypothesis Calculate error

THEN, make your judgment (conclusion)

Measurement & Significant Figures

Nature of Measurement

MeasurementMeasurement - quantitative observation - quantitative observation consisting of 2 partsconsisting of 2 parts

Part 1 – numberPart 1 – number

Part 2 - scale (unit)Part 2 - scale (unit)

Examples:Examples:20 grams20 grams

6.63 6.63 Joule seconds Joule seconds

International System(le Système International)

Based on metric system and units Based on metric system and units derived from metric system.derived from metric system.

*Called *Called SI unitsSI units**

The Fundamental SI Units

Derived Units

Units obtained by a mathematical operation performed on base units.

Area L x W cm x cm = cm2

Volume L x W x H cm x cm x cm = cm3

Density mass / volume g / mL

Accuracy and Precision

• AccuracyAccuracy refers to the agreement of a refers to the agreement of a particular value with theparticular value with the truetrue value.value.

• Precision Precision refers to the degree of refers to the degree of agreement among several elements of agreement among several elements of the same quantity.the same quantity.

Label each experiment

True Value = 5.000g

Accurate & Precise Precise but not accurate

Trial 1 – 5.003g Trial 1 – 5.500g

Trial 2 – 5.002g Trial 2 – 5.503g

Trial 3 – 5.001g Trial 3 – 5.499g

Neither Accurate or Precise

Trial 1 – 5.400g

Trial 2 – 5.200g

Trial 3 – 5.905g

Uncertainty in Measurement

A digit that must be A digit that must be estimatedestimated is called is called uncertainuncertain. A . A measurementmeasurement always has always has

some degree of uncertainty.some degree of uncertainty.

Reading measuring devices

Try Again

How long is the green line?

Rules for Counting Significant Figures - Overview

1.1. Nonzero integersNonzero integers

2.2. ZerosZeros• leading zerosleading zeros• captive zeroscaptive zeros• trailing zerostrailing zeros

3.3. Exact numbersExact numbers

Rules for Counting Significant Figures - Details

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

3456 3456 has has

4 4 sig figs.sig figs.

Rules for Counting Significant Figures - Details

ZerosZeros• Leading zerosLeading zeros do not count as do not count as

significant figures.significant figures.

0.00.0486486 has has

33 sig figs. sig figs.

Rules for Counting Significant Figures - Details

ZerosZeros• Captive zerosCaptive zeros always count as always count as

significant figures.significant figures.

16.16.007 7 hashas

4 4 sig figs.sig figs.

Rules for Counting Significant Figures - Details

ZerosZeros• Trailing zerosTrailing zeros are significant only are significant only if the if the

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

9.39.30000 has has

44 sig figs. sig figs.

Rules for Counting Significant Figures - Details

ZerosZeros• Trailing zerosTrailing zeros are are notnot significant when significant when

there is there is notnot a decimal point a decimal point

93930000 has has

22 sig figs. sig figs.

Zero’s Chant

Leading zeros never count,

Captive zeros always count,

Trailing zeros only count if there’s a decimal in the number!

Rules for Significant Figures in Mathematical Operations

Multiplication and DivisionMultiplication and Division: : # sig figs in # sig figs in the result equals the number in the least the result equals the number in the least precise measurement used in the precise measurement used in the calculation.calculation.

6.38 6.38 2.0 = 2.0 =

12.76 12.76 13 (2 sig figs)13 (2 sig figs)

Rules for Significant Figures in Mathematical Operations

Addition and SubtractionAddition and Subtraction: : # sig figs in # sig figs in the result equals the number of the result equals the number of decimadecimall placesplaces in the least precise in the least precise measurement.measurement.

6.8 + 11.934 =6.8 + 11.934 =

18.734 18.734 18.718.7

Scientific Notation and Dimensional Analysis

How to use these tools

Scientific Notation - Overview

Used to make really large or small numbers manageable.

Consists of 2 parts:– A number with only 1 number to the left of the

decimal place (base number)– 10 to a power, either + or –

5.234 x 103 8 x 10-5 106 = 1 x 106

Scientific Notation - Overview

If the 10 has a + power the decimal moves to the right

Ex. 1.5 x 103 = 1500 If the 10 has a - power the decimal moves to

the left

Ex. 3.5 x 10-6 = 0.0000035 All BASE numbers are significant digits!

Scientific Notation – With Calculator

Use the “2nd” then “,” to enter the “EE” which stands for the x10

Use the “(-)” to change to negative exponent if negative

Enter the number of the exponent

Scientific Notation – With Calculator

Examples:

1. (5.4 x 103) + (6.00 x 102) =

5.4 “EE” 3 + 6 “EE” 2 =

2. (3.42 x 10-5) – (2.5 x 10-6) =

3.42 “EE” “(-)” 5 – 2.5 “EE” “(-)” 6 =

Scientific Notation – With Calculator

3. (6.5 x 10-5)(3.5 x 106) =

6.5 “EE” “(-)” 5 x 3.5 “EE” 6 =

4. 10-8 / 103 =

1 “EE” “(-)” 8 ÷ 1 “EE” 3 =

Dimensional Analysis

Organized approach to problem solving Uses conversion factors to find your desired

outcome– Conversion factors: any two quantities that

are equal– Ex. 1 in = 2.54 cm; 1 lb = 454 g; 1 qt = 946

mL

Dimensional Analysis

It is basically multiplying fractions! Units cancel diagonally until you are left with

your desired unit Solve by multipling the numbers above the

line & dividing the numbers below the line

Dimensional Analysis

1. Write down the units you are looking for.2. Write down the number & unit given in the

problem.3. Decide what conversion factor(s) you need

to use.4. Cancel Units which are diagonal5. Multiply everything above and below the

line.6. Divide the number above the line by the

number below the line.

Dimensional Analysis

1. ? Seconds has a 16 year old lived.

2. ? Lbs is a 200,000 g sumo wrestler.

3. ? L in a 6 pack (ea. 12 oz) of soda.

Dimensional Analysis – Metric Units

1. Base Units (pg 26) - mass: grams - length: meters - volume: liters - time: sec - temp: °C, K - amt: mole

2. Based on powers of 10- Common Prefixes and powers

kilo k 103

centi c 10-2

milli m 10-3

micro μ 10-6

nano n 10-9

Dimensional Analysis – Metric Units

1. Go from beginning unit to stem (meter, liter, gram, second)

2. Go from stem to unit that you want

3. Always use a whole (+) positive exponent number

4. Put the + number as the exponent of the smaller unit

Matter: Properties & Changes

Subtopics: Density & Graphing

States of Matter

Solid– Molecules or atoms in a rigid pattern

(crystal lattice)– High intermolecular attractions– Definite shape and volume

Liquid– Particles not in definite pattern– Relatively high intermolecular

attraction– Definite volume = shape of container

States of Matter

Gas– Particles have no pattern– Low intermolecular attraction– No definite shape or volume

Properties of Matter

What is a Property?– Characteristics that describe matter or how it behaves

Physical – determined without a chemical change

– Extensive – vary with amount of matter (Ex. Mass, volume, length, area)

– Intensive – does not vary with amount (Ex. Density, color, odor, melting point, solubility)

Chemical – can only be determined by a chemical change

Ex. Flammability, reactivity with acid, stability of a compound (how easily it decomposes)

Changes of Matter

Physical Changes – does not involve a change in chemical identity– Ex: boiling, freezing, melting, dissolving,

evaporating, and crystallizing

Changes of Matter

Chemical Changes – new substances are formed in the reaction– Ex: iron rusting,

copper oxidizing, wood burning, silver tarnishing

Evidence for Changes of Matter

Color Change Gas produced without

heating Precipitate formed New odor develops Large amount of heat

or light produced

Energy in Chemical Reactions

All chemical changes also involve some sort of energy change.

Energy is either taken in or given off as the chemical change takes place.

– Exothermic: heat energy is released– Endothermic: heat energy is

absorbed Photosynthesis is probably the most

important endothermic process on earth.

Density

Mass per unit volume (mass/volume)

Units:– Liquids - g/mL or g/cm3

– Gases - g/L

Density

Density remains constant (same ratio) for a material unless temperature changes.

A gold bar is cut in half. What happened to its density?

What happened to its value?

Graphing

1. Use graph paper.2. Use a ruler to draw axes.3. Choose a descriptive title.

• Relate info on the 2 axes.• Ex: Relationship of Mass to Volume

4. Label axes & give units of measurement. Ex. Temperature (°C)

5. Choose a scale that will fill entire page.• You do not have to start with zero in the corner!• Subtract lowest from highest value ÷ by # lines.

Graphing

6. Plot data points & circle each point (point protector)

7. Draw a Best Fit Line (smooth line) or curve to indicate a general trend of data points.

DO NOT CONNECT DOT TO DOT!

8. Extrapolate data beyond data points using dotted lines.

End of Unit 1 Notes!

Prepare for the Unit 1 Test on 9/11/2008