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Chapter 1

Chemical Foundations

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Theory or Law

Evolution?

Atomic system?

The germ theory of illness?

The heliocentric solar system?

Gravity?

Heat transfer?

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Theory or Law

1. Studying more hours will ensure you will get an A+ in Chem101.

2. Solving large number of old exams would increase your grades in Chem101.

3. Drinking a lot of water is better for your health.4. Doing sport will keep you healthy.5. Basketball will always move downward.6. A hot body will cool with time.7. Conservation of mass

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Steps in the Scientific Method

1.1. ObservationsObservations

quantitativequantitative

qualitativequalitative

2.2. Formulating hypothesesFormulating hypotheses

possible explanation for the observationpossible explanation for the observation

3.3. Performing experimentsPerforming experiments

gathering new information to decidegathering new information to decide

whether the hypothesis is validwhether the hypothesis is valid

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Outcomes Over the Long-Term

Theory (Model)Theory (Model)

A set of tested hypotheses that give anA set of tested hypotheses that give an overall explanation of some overall explanation of some

natural natural phenomenon.phenomenon.

Natural LawNatural Law

The same observation applies to manyThe same observation applies to many different systemsdifferent systems

Example - Law of Conservation of Example - Law of Conservation of MassMass

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Law and Theory

A A lawlaw summarizes what happens; summarizes what happens;

A A theorytheory (model) is an attempt to (model) is an attempt to explain explain whywhy it happens. it happens.

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Figure 1.4: The fundamental steps of the scientific method.

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Figure 1.5: The various parts of the scientific method.

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Hypothesis

A hypothesis is an educated guess, based on observation. Usually, a hypothesis can be supported or refuted through experimentation or more observation. A hypothesis can be disproven, but not proven to be true.

Example: If you see no difference in the cleaning ability of various laundry detergents, you might hypothesize that cleaning effectiveness is not affected by which detergent you use. You can see this hypothesis can be disproven if a stain is removed by one detergent and not another. On the other hand, you cannot prove the hypothesis. Even if you never see a difference in the cleanliness of your clothes after trying a thousand detergents, there might be one you haven't tried that could be different.

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Theory

A scientific theory summarizes a hypothesis or group of hypotheses that have been supported with repeated testing. A theory is valid as long as there is no evidence to dispute it. Therefore, theories can be disproven. Basically, if evidence accumulates to support a hypothesis, then the hypothesis can become accepted as a good explanation of a phenomenon. One definition of a theory is to say it's an accepted hypothesis.

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Example of a Theory

Example: It is known that on June 30, 1908 in Tunguska, Siberia, there was an explosion equivalent to the detonation of about 15 million tons of TNT. Many hypotheses have been proposed for what caused the explosion. It is theorized that the explosion was caused by a natural extraterrestrial phenomenon, and was not caused by man. Is this theory a fact?

No.

The event is a recorded fact. Is this theory generally accepted to be true, based on evidence to-date?

Yes.

Can this theory be shown to be false and be discarded?

Yes.

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Example of a LawA law generalizes a body of observations. At the time it is made, no

exceptions have been found to a law. Scientific laws explain things, but they do not describe them. One way to tell a law and a theory apart is to ask if the description gives you a means to explain 'why'.

Example: Consider Newton's Law of Gravity. Newton could use this law to predict the behavior of a dropped object, but he couldn't explain why it happened.

As you can see, there is no 'proof' or absolute 'truth' in science. The closest we get are facts, which are indisputable observations. Note, however, if you define proof as arriving at a logical conclusion, based on the evidence, then there is 'proof' in science. I work under the definition that to prove something implies it can never be wrong, which is different. If you're asked to define hypothesis, theory, and law, keep in mind the definitions of proof and of these words can vary slightly depending on the scientific discipline. What is important is to realize they don't all mean the same thing and cannot be used interchangeably.

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Nature of Measurement

Measurement - quantitative observation consisting of Measurement - quantitative observation consisting of 2 parts2 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

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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.

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The Fundamental SI Units

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Figure 1.6: Measurement of volume

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Figure 1.7: Common types of laboratory equipment used to measure liquid volume.

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Figure 1.8: An electronic analytical balance.

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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.

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Figure 1.9: Measurement of volume using a buret. The volume is read at the bottom of the liquid curve (called the meniscus).

20.16ml20.17ml20.15ml20.18ml

±0.01ml

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Precision and Accuracy

Accuracy Accuracy refers to the agreement of a refers to the agreement of a particular value with theparticular value with the true true value.value.

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

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Figure 1.10: The results of several dart throws show the difference between precise and accurate.

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Types of Error

Random Error Random Error (Indeterminate Error) - (Indeterminate Error) - measurement has an equal probability of measurement has an equal probability of being high or low.being high or low.

Systematic Error Systematic Error (Determinate Error) - (Determinate Error) - Occurs in the Occurs in the same directionsame direction each time (high each time (high or low), often resulting from poor technique.or low), often resulting from poor technique.

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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

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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.

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Rules for Counting Significant Figures - Details

ZerosZerosLeading zerosLeading zeros do not count as do not count as

significant figures.significant figures.

0.04860.0486 has has

33 sig figs. sig figs.

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Rules for Counting Significant Figures - Details

ZerosZeros Captive zerosCaptive zeros always count as always count as

significant figures.significant figures.

16.07 16.07 hashas

4 4 sig figs.sig figs.

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Rules for Counting Significant Figures - Details

ZerosZeros Trailing zerosTrailing zeros are significant only are significant only

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

9.3009.300 has has

44 sig figs. sig figs.

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Rules for Counting Significant Figures - Details

Exact numbersExact numbers have an infinite number of significant have an infinite number of significant figures.figures.

Independent of measuring device:Independent of measuring device:1 apple, 10 students, 5 cars….1 apple, 10 students, 5 cars….

22ππr The 2 is exact r The 2 is exact 4/3 4/3 ππ r r22 the 4 and 3 are exact the 4 and 3 are exact

From Definition: 1 inch = 2.54 cm exactlyFrom Definition: 1 inch = 2.54 cm exactlyThe 1 and 2.54 do not limit the significant figuresThe 1 and 2.54 do not limit the significant figures

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100. has 3 sig. fig. = 1.00 x 102

100 has 1 sig. fig. = 1 x 102

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Rules For Rounding

1. In a series of calculations, carry the extra digits through to the final result, then round.

2. If the digit to be removed:A. Is less than 5, then no change e.g. 1.33 rounded to 2

sig. fig = 1.3

B. Is equal or greater than 5, the preceding digit increase by 1 e.g. 1.36 rounded to 2 sig. fig = 1.4

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Rules for Significant Figures in Mathematical Operations

Multiplication and Division: Multiplication 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 calculation.precise measurement used in the calculation.

6.38 6.38 2.0 = 2.0 =

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

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Rules for Significant Figures in Mathematical Operations

Addition and Subtraction: Addition and Subtraction: # decimal places # decimal places in the result equals the number of decimal in the result equals the number of decimal places in the least precise measurement.places in the least precise measurement.

6.8 + 11.934 =6.8 + 11.934 =

18.734 18.734 18.7 (3 sig figs)18.7 (3 sig figs)

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Rules for Counting Significant Figures.

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Dimensional Analysis

Proper use of “unit factors” leads to proper units in Proper use of “unit factors” leads to proper units in your answer: your answer:

2.54 cm = 1 inch2.54 cm = 1 inch

1 inch/2.54 cm = 1 Unit factor1 inch/2.54 cm = 1 Unit factor

What is the length in inch of 2.85 cm pencilWhat is the length in inch of 2.85 cm pencil

2.85 (cm) x 1 (inch)/2.54(cm) = 2.85/2.54 = 1.12 in2.85 (cm) x 1 (inch)/2.54(cm) = 2.85/2.54 = 1.12 in

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Dimensional Analysis

1. Determine which unit conversion factor(s) are needed

2. Carry units through calculation

3. If all units cancel except for the desired unit(s), then the problem was solved correctly.

1 L = 1000 mL

How many mL are in 1.63 L?

1L

1000 mL1.63 L x = 1630 mL

1L1000 mL

1.63 L x = 0.001630L2

mL

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Scientific NotationThe number of atoms in 12 g of carbon:

602,200,000,000,000,000,000,000

6.022 x 1023

The mass of a single carbon atom in grams:

0.0000000000000000000000199

1.99 x 10-23

N x 10n

N is a number between 1 and 10

n is a positive or negative integer

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Scientific Notation568.762

n > 0

568.762 = 5.68762 x 102

move decimal left

0.00000772

n < 0

0.00000772 = 7.72 x 10-6

move decimal right

Addition or Subtraction

1. Write each quantity with the same exponent n

2. Combine N1 and N2 3. The exponent, n, remains

the same

4.31 x 104 + 3.9 x 103 =

4.31 x 104 + 0.39 x 104 =

4.70 x 104

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Temperature

Celsius scale =Celsius scale =CCKelvin scale = KKelvin scale = K

Fahrenheit scale =Fahrenheit scale =FF

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Temperature

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Figure 1.11: The three major temperature scales.

180/100= 9/5

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TFTc

0100

0

32212

32

cF TT

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Figure 1.12: Normal body temperature on the Fahrenheit, Celsius, and Kelvin scales.

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Density

Density Density is the mass of substance per unitis the mass of substance per unit

volume of the substance:volume of the substance:

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Matter:Matter: Anything occupying Anything occupying

space and having mass.space and having mass.

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Classification of Matter

Three States of Matter:Three States of Matter:

Solid: rigid - fixed volume and shapeSolid: rigid - fixed volume and shape

Liquid: definite volume but assumes the Liquid: definite volume but assumes the shape of its containershape of its container

Gas: no fixed volume or shape - assumes Gas: no fixed volume or shape - assumes the shape of its containerthe shape of its container

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Types of Mixtures

Mixtures have variable composition.Mixtures have variable composition.

AA homogeneous mixturehomogeneous mixture is a solution (for is a solution (for example, vinegar)example, vinegar)

AA heterogeneous mixtureheterogeneous mixture is, to the naked is, to the naked eye, clearly not uniform (for example, a eye, clearly not uniform (for example, a bottle of ranch dressing)bottle of ranch dressing)

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Pure Substances

Can be isolated by separation methods:Can be isolated by separation methods:

ChromatographyChromatography

FiltrationFiltration

DistillationDistillation

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Figure 1.15a: Paper chromatography of ink. (a) A line of the mixture to be separated is placed at one end of a sheet of

porous paper.

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Figure 1.15b: Paper chromatography of ink. (b) The paper acts as a wick to draw up the liquid.

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Figure 1.15c: Paper chromatography of ink. (c) The component with the weakest attraction for the paper travels faster than the components that cling to the paper.

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Figure 1.14: Simple laboratory distillation apparatus.

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Element:Element: A substance that cannot be A substance that cannot be decomposed into simpler substances by decomposed into simpler substances by chemical means.chemical means.

Compound:Compound: A substance with a A substance with a constant composition that can be constant composition that can be broken down into elements by broken down into elements by chemical processes.chemical processes.

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Figure 1.16: The organization of matter.

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Q1.Express the result of this calculation to the correct number of significant figures.

A) 188.1B) 188C) 188.12D) 190.E) 200.

4326.0

705.80

623.0

470.0

1.3

526.2

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QUESTIONWhich of the following is an example of a quantitative observation? 1) The piece of metal is longer than the piece

of wood 2) Solution 1 is much darker than solution 2. 3) The liquid in beaker A is blue. 4) The temperature of the liquid is 60°C. 5) At least two of these (1–4) are quantitative

observations.

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ANSWER4) The temperature of the liquid is 60°C. Section 1.2 The Scientific Method (p. 7) A quantitative observation involves a number and a unit of measure. A qualitative observation is a statement of the “qualities” of a system. For example the sky is blue or a chemical reaction produces heat.

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QUESTIONGenerally observed behavior that can be formulated into a statement, sometimes mathematical in nature, is called a(n) 1) observation. 2) measurement. 3) theory. 4) natural law. 5) experiment.

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ANSWER4) natural law. Section 1.2 The Scientific Method (p. 7) A natural law is a theory that applies to many different systems across several disciplines. The Law of Conservation of Mass is an example.

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ANSWER (continued)Its application is necessary to study any chemical reaction and these reactions are not only used in chemistry, but in biology, geology, various fields of engineering and physics.

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QUESTIONWhat is the measure of resistance an object has to a change in its state of motion? 1) Mass 2) Weight 3) Volume 4) Length 5) None of these

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ANSWER1) Mass Section 1.3 Units of Measurement (p. 10) This measure of resistance is called inertia.

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QUESTIONA titration was performed to find the concentration of hydrochloric acid with the following results: Trial Molarity 1 1.25 ± 0.01 2 1.24 ± 0.01 3 1.26 ± 0.01

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QUESTION (continued)

The actual concentration of HCl was determined to be 1.000 M; the results of the titration are: 1) both accurate and precise. 2) accurate but imprecise. 3) precise but inaccurate. 4) both inaccurate and imprecise. 5) accuracy and precision are impossible to

determine with the available information.

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ANSWER3) precise but inaccurate. Section 1.4 Uncertainty in Measurement (p. 13) Accuracy is the agreement of a particular value with the true value. None of the values is close to the true value so they are not accurate measurements. Precision refers to the degree of agreement among several measurements.

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ANSWER (continued)These measurements are relatively close together, so they have a high degree of precision.

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QUESTIONWhich of the following is the least probable concerning five measurements taken in the lab? 1) The measurements are accurate and precise. 2) The measurements are accurate but not

precise. 3) The measurements are precise but not

accurate. 4) The measurements are neither accurate nor

precise. 5) All of these are equally probable.

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ANSWER2) The measurements are accurate but not

precise. Section 1.4 Uncertainty in Measurement (p. 13) If the balances in the lab have been recently standardized, the measurements should be both accurate and precise.

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ANSWER (continued)If the balances are working correctly they will have high precision, but may not be standardized and may thus be inaccurate. If the balance is broken—this can happen by damage from spilled chemicals—it may be both inaccurate and imprecise. It is highly unlikely that a balance will have low precision and still be accurate.

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QUESTIONThe amount of uncertainty in a measured quantity is determined by: 1) both the skill of the observer and the

limitations of the measuring instrument. 2) neither the skill of the observer nor the

limitations of the measuring instrument. 3) the limitations of the measuring instrument

only. 4) the skill of the observer only. 5) none of these

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ANSWER1) both the skill of the observer and the

limitations of the measuring instrument. Section 1.4 Uncertainty in Measurement (p. 11) The limitations of the measuring instrument will of course be very important to the quality of the measurement, but a skilled and attentive

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ANSWER (continued)observer is necessary to operate the measuring device correctly. Mistakes by an observer are very common and are part of experimental error.

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QUESTIONHow many significant figures are there in the number 0.04560700? 1) 4 2) 5 3) 7 4) 8 5) 9

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ANSWER3) 7 Section 1.5 Significant Figures and Calculations (p. 14) Leading zeros are never counted, while trailing zeros, to the right of the decimal point, are always counted.

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QUESTIONOne second contains this many picoseconds. 1) 1 10

12

2) 1 10–12

3) 1 10

–9

4) 1 109

5) 1 1015

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ANSWER

1) 1 1012

Section 1.3 Units of Measurement (p. 8) pico means 10

–12, or one trillionth. A picosecond

is one trillionth of a second. Therefore there are one trillion, 10

12, picoseconds in one second.

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QUESTION100 seconds contain this many nanoseconds. 1) 1 10

7

2) 1 1011

3) 1 10

10

4) 1 1012

5) 1 10

8

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ANSWER

2) 1 1011

Section 1.3 Units of Measurement (p. 8) nano means 10

–9, or one billionth. A

nanosecond is one billionth of a second. Therefore there are one billion, 10

9,

nanoseconds in one second and 100 109 =

1011

nanoseconds in 100 seconds.

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QUESTIONHow many significant figures are there in the number 0.0006042? 1) 7 2) 3 3) 8 4) 4 5) 0

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ANSWER4) 4 Section 1.5 Significant Figures and Calculations (p. 15) The four leading zeros are placeholders and are not counted toward the number of significant figures.

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QUESTIONConvert 6.0 kg to lb. (1 kg = 2.205 lb). 1) 13 lbs 2) 1.3 lbs 3) 2.7 lbs 4) 10. lbs 5) 13.23 lbs

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ANSWER1) 13 lbs Section 1.6 Dimensional Analysis (p. 18) 6.0 kg is a measurement with two significant figures. The conversion factor has four significant figures. According to the rules of significant figures the answer will have two significant figures.

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QUESTION423 Kelvin equals: 1) 150. F 2) 273. F 3) 696. F 4) 150. C 5) 696. C

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ANSWER

4) 150. C Section 1.7 Temperature (p. 22) The measurement of temperature in Kelvins is the measurement in Celsius + 273.

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QUESTIONThe state of matter for an object that has a definite volume but not a definite shape is 1) solid state. 2) liquid state. 3) gaseous state. 4) elemental state. 5) mixed state.

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ANSWER2) liquid state. Section 1.9 Classification of Matter (p. 27) The indefinite shape of a liquid allows it to form to the shape of any container it is placed in. It will settle to the bottom of the container and form a surface, unlike a gas, which will fill the entire volume of the container.

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QUESTIONThe density of gasoline is 0.7025 g/mL at 20°C. When gasoline is added to water 1) it will float on top. 2) it will sink to the bottom. 3) it will mix so you can’t see it. 4) the mixture will improve the running of the

motor. 5) none of these things will happen.

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ANSWER1) it will float on top. Section 1.8 Density (p. 25) The particles (atoms, molecules) of the denser material feel a stronger pull of gravity per volume than the less dense material and are pulled closer to the center of the Earth.

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QUESTIONA solution is also called a 1) homogeneous mixture. 2) heterogeneous mixture. 3) pure mixture. 4) compound. 5) distilled mixture.

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ANSWER1) homogeneous mixture. Section 1.9 Classification of Matter (p. 27) A solution is mixed to the molecular level. There are no “clumps” of salt in a solution of saltwater; the ions are evenly distributed throughout the water.

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QUESTIONAn example of a pure substance is 1) elements. 2) compounds. 3) pure water. 4) carbon dioxide. 5) all of these

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ANSWER5) all of these Section 1.9 Classification of Matter (p. 28) A pure substance can be either an element or a compound. Water is a compound as is carbon dioxide. Saltwater and air are examples of mixtures.

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QUESTIONAs warm water sits in a cool room, you measure the temperature change. Which of the following is true?

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QUESTION (continued)

1) The temperature change is bigger if you are measuring in °F.

2) The temperature change is bigger if you are measuring in °C.

3) The temperature change will be the same regardless of the scale you use.

4) Answer 1 or 2 is correct, depending on the difference in temperature between the water and the room.

5) none of these

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ANSWER1) The temperature change is bigger if you are

measuring in °F. Section 1.7 Temperature (p. 24) For every 1 degree change on the Celsius scale, there is a change of 1.8 degrees on the Fahrenheit scale.

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QUESTIONColor changes always indicate a chemical change.

1) True 2) False

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ANSWER2) False Section 1.7 Temperature (p. 29) Combining a red dye and a green dye will produce a blue mixture, but this does not alter the chemical structure of the two dyes.

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QUESTIONA chemical theory that has been known for a long time becomes a law.

1) True 2) False

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ANSWER2) False Section 1.2 The Scientific Method (p. 7) A theory concerning a very specific chemical or physical phenomenon, will not be general enough to be considered law.

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ANSWER (continued)The discovery of a theory to model the amount of mail one gets each day, may have significance to that person and possibly to the Post Office, but could not be considered a law due to its specificity.