Chapter 1 - Measurements

Ch. 1: Intro: Matter and MeasurementLearning GoalsKnow the components of the scientific methodKnow how matter can be classified into subgroupsKnow and use SI system of units and prefixesIdentify and use significant figures Perform conversions among the temperature scalesPerform calculations involving density

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ChemistryScience that studies the composition and structure of matter, changes in matter and changes in energy Matter - anything that volume (occupies space) and has mass [can be perceived by our senses]Mass - quantity of matter does not vary with locationWeight - force of gravity on mattervaries with locationEnergy ability to do work *

2009, Prentice-Hall, Inc.Scientific MethodThe scientific method is simply a systematic approach to solving problems.

Goal: Understand the Components of the Scientific Method1.1.The Scientific MethodHow do we distinguish between a hypothesis and a theory?Hypothesis: Educated guess to explain observation.Theory: tries to explain why nature behaves the way it does.How do we distinguish between a law and a theory?Law: Simply says what happens; does not explain whyHow do we setup a valid experiment?Compare and contrast dataQualitative: does not rely on a number, i.e.: crystalline sulfur is yellowQuantitative: measurements a # and unit

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Exercise : Classify 1. Ice always floats on liquid water

LawTheoryExperimentHypothesisQualitative observationQuantitative observation

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2. Hot air is less dense than cold air because the components of hot air are moving more rapidlyLawTheoryExperimentHypothesisQualitative observationQuantitative observation*

3. When 10 g of ice was added to 100 mL of water at 25C, the temperature of the water decreased to 15.5 C after the ice meltedLawTheoryExperimentHypothesisQualitative observationQuantitative observation*

1.2 Classification Based on Composition: Pure SubstancesConstant or fixed composition throughoutChanges of state occur at a constant temperature Components are inseparable using physical methodsExamples: aluminum, molcular oxygen, water

*Goal: Classify Matter as Pure Substance or Mixture

1.2 Classification Based on Composition: Pure SubstancesSubclassification: Element Pure substance that cannot be decomposed into simpler substances by chemical or physical meansSmallest unit of an element - atom Learn names & symbols for: 1-38, 46-56, 74, 78-80, 82, 86*

1.2. Classification Based on Composition: Pure SubstancesAB CExercise: Consider the physical and chemical characteristics of these three samples. Based on these, why are they classified as pure substances? Take 1 minute to write your thoughts. Take another to discuss with your neighbor.*

Classification Based on Composition: Pure SubstancesSubclassification: CompoundPure substances composed of two or more elements chemically combined in constant or fixed proportions (law of definite proportion)Compounds can be broken down into elements by chemical processes

The chemical formula of a substance is a notation using atomic symbols with subscripts to convey the relative proportions of atoms of the different elements in a substance*

Learning Check The composition of a sample was determined in triplicate. Results: pure substance (law of conservation of mass)pure substance (law of definite proportions)mixture (law of conservation of mass) mixture (law of definite proportions)*# mass sple. mass Cu mass C mass O 1103 g 53 g10. g40 g275 g 28 g14 g33 g3145 g 79 g38 g 28 g

Classification Based on Composition: MixturesCombination of 2 or more pure substances in which the substances retain their distinct identitiesComposition variableComponents may be separated by physical methodsChange of state occurs over a range of temperaturesSubclassificationHomogeneous (a.k.a. solutions) uniform in its properties throughoutHeterogeneous has physically distinct parts, each with different properties*

Classification Based on Composition: MixturesExercise: Consider the physical and chemical characteristics of these three samples. Based on these, why are they classified as mixtures? Take 1 minute to write your thoughts. Take another to discuss with your neighbor.*

Classification of Matter Based On Composition *("Chemistry, Ebbing & Gammon, 2007)

Classify & Sub-classify Based on Chemical ConstitutionQuiz*

Goal: Classify Properties and Changes as Physical or ChemicalPhysical Property: can be observed w/o changing the identity and composition of the substance.Chemical Property: Describes the way a substance may change or react.Physical Change: Substance changes appearance, but not composition.Chemical Change: Substance transforms into a chemically different substance.*

*PhysicalChemicalProperties

*Change: Physical or Chemical?

PropertyWater boils at 100oC _______Diamonds are capable of cutting glass. __________Water can be separated by electrolysis into hydrogen and oxygen. _________Sugar is capable of dissolving in water. _________Wood is flammable. _________ChangeSand and water are separated when passed through a filter. ____Yeast acts on sugar to form carbon dioxide and ethanol. _______Dry ice forms a vapor cloud upon heating__________Iron rusts in a damp environment. ___________Gasoline burns in the presence of oxygen. Burning a candle ______________Physical or Chemical?*

Separation of Mixtures 2009, Prentice-Hall, Inc.

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2009, Prentice-Hall, Inc.DistillationDistillation uses differences in the boiling points of substances to separate a homogeneous mixture into its components.

2009, Prentice-Hall, Inc.FiltrationIn filtration solid substances are separated from liquids and solutions.

2009, Prentice-Hall, Inc.ChromatographyThis technique separates substances on the basis of differences in solubility in a solvent.

Goal: Understand limitation in measurements, and how to properly report calculations*

1.4 Measurement of Matter: SI UnitsInternational System of Units, SILength Mass Volume Temperature Time

*meter, m 1 m = 3.281 ft = 39 incheskilogram, kg 1 kg = 2.205 lb

liter, L (1dm3), mL (cm3) 1 tsp = 5 mL 2 tbs = 1 oz .946 L = 1 qt

Kelvin, K

Seconds, s

2009, Prentice-Hall, Inc.VolumeThe most commonly used metric units for volume are the liter (L) and the milliliter (mL).A liter is a cube 1 dm long on each side.A milliliter is a cube 1 cm long on each side.

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Prefixes Used in the Metric System

Review the SelectedSI Prefixes You Need toMemorize

2009, Prentice-Hall, Inc.Metric SystemPrefixes convert the base units into units that are appropriate for the item being measured. (Table 1.5, p. 14)

Sample Exercise 1.2 Using Metric PrefixesWhat is the name given to the unit that equals (a) 10-9 gram, (b) 10-6 second, (c) 10-3 meter?Answer: (a) 10-12 second, (b) 6.0 km, (c) 3.76 103 g

1.5. MeasurementsComparison of a known quantity with an unknown quantityConsists of a number and a unitSubject to errorSignificant FiguresLimited by the measuring toolConsist of all digits known with certainty, plus one of uncertain value

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Rules for Significant FiguresAll non-zero numbers are significant.Leading zeros are NEVER significant. 0.6 only has 1 s.f.0.06 only has 1 s.f.Captive zeros are ALWAYS significant. 208 has 3 s.f.20008 has 5 s.f.*

Trailing zeros are significant ONLY when a decimal is present.50 has 1 s.f.50. has 2 s.f.50.0 has 3 s.f.*

Learning Check Counting Sig. Figs. I. Which answers contain 3 significant figures?(1) 0.060 (2) 410 (3) 1.00

1231 and 21 and 32 and 3All

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Learning Check Counting Sig. Figs. II. All zeros are significant in (1) 9.0030 (2) 2500 (3) 0.08001231 and 21 and 32 and 3All*

* Reviewrules regarding calculationsand rounding

Significant Figures and RoundingWhen addition or subtraction is performed, answers are rounded to the least significant decimal place.When multiplication or division is performed, answers are rounded to the number of digits that corresponds to the least number of significant figures in any of the numbers used in the calculation.

Sample Exercise 1.7 Determining the Number of Significant figures in a Calculated QuantityThe width, length, and height of a small box are 15.5 cm, 27.3 cm, and 5.4 cm, respectively. Calculate the volume of the box, using the correct number of significant figures in your answer.Answer: 9.52 m/s (three significant figures)

Sample Exercise 1.8 Determining the Number of Significant figures in a Calculated QuantityA gas at 25 C fills a container whose volume is 1.05 103 cm3. The container plus gas have a mass of 837.6 g. The container, when emptied of all gas, has a mass of 836.2 g. What is the density of the gas at 25 C?

Sample Exercise 1.8 Determining the Number of Significant figures in a Calculated QuantityAnswer: five (For the difference in the two masses to have three significant figures, there must be two decimal places in the masses of the filled and empty containers. Therefore, each mass must be measured to five significant figures.)

Goal: Perform calculations that will be used often in the course: - conversions in metric system - density - temperature. *

2009, Prentice-Hall, Inc.Dimensional AnalysisWe use dimensional analysis to convert one quantity to another.Most commonly dimensional analysis utilizes conversion factors (e.g., 1 in. = 2.54 cm)or

Dimensional AnalysisUse the form of the conversion factor that puts the sought-for unit in the numerator.

Dimensional AnalysisFor example, to convert 8.00 m to inches,convert m to cmconvert cm to in.8.00 m

Exercises: Identify the measurement and perform the conversion Convert 26 g to mgAns. = 26000 mgConvert 1250 L to LAns. = 0.00125 LConvert 2720 Km to MmAns. = 2.72 Mm

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Learning Check:Convert 0.231 Kg to gNA 231 g0.231g2.31 x 108 g2.31 x 10-8 g*

2009, Prentice-Hall, Inc.TemperatureBy definition temperature is a measure of the average kinetic energy of the particles in a sample.

2009, Prentice-Hall, Inc.TemperatureIn scientific measurements, the Celsius and Kelvin scales are most often used.The Celsius scale is based on the properties of water.0C is the freezing point of water.100C is the boiling point of water.

2009, Prentice-Hall, Inc.TemperatureThe Kelvin is the SI unit of temperature.It is based on the properties of gases.There are no negative Kelvin temperatures.K = C + 273.15

2009, Prentice-Hall, Inc.TemperatureThe Fahrenheit scale is not used in scientific measurements.F = 9/5(C) + 32C = 5/9(F 32)Note regarding significant digits: answer must have the same number of decimal places as the original temperature.

Exercise: Calculate TLiquid nitrogen (N2 ), which has a freezing point of -210.C, is often used to remove warts and to treat precancerous skin lesions. Convert this temperature into Kelvin.

A person with hypothermia has a body temperature of 84.4F. What is the body temperature in C?

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*Measurement of Matter: Density (A Derived Unit)Definition ________________Ex. What occupies a greater volume: 1 kilogram of rock or 1 kilogram of aluminum foil? Which has a higher density: rock or aluminum foil? Which has a greater density: 1 g of water or 10 g of water? Which has a greater density: 1 g of rock or 10 g of aluminum foil?

*Density ExercisesWhat is the average density of a loaf of bread that has a mass of 501 g and a volume of 1000.0 mL ?A sack of groceries accidentally set on the above loaf increased its density to 2.1 grams per milliliter. What is its new volume? High-density polyethylene (HDPE) is a strong, stiff, opaque polymer that is used to make may things, including grocery bags, pipes and packaging. What is the mass in kg of 834.6 mL of HDPE that has a density of 0.960 g/mL?

(a) Calculate the density of mercury if 1.00 102 g occupies a volume of 7.36 cm3. (b) Calculate the volumeof 65.0 g of the liquid methanol (wood alcohol) if its density is 0.791 g/mL. (c) What is the mass in grams ofa cube of gold (density = 19.32 g/cm3) if the length of the cube is 2.00 cm?Sample Exercise 1.4 Determining Density and Using Density to Determine Volume or Mass

Answers: (a) 8.96 g/cm3, (b) 19.0 mL, (c) 340 g

Chapter 1 Vocabulary TermsUse the index and slides to help you with definitions*

Ch. 1: Matter and MeasurementReview the Learning Goals in Slide 1Complete the homework assignment earlyAsk questions in classVisit/call Prof. Tice during office hoursReview any practice problems in Sapling Learning or unassigned problems in your textbookUtilize study aids listed in the syllabus

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matter- stuff of which material things are madeChemistry is a central science. It is fundamental to other scientific disciplines, as well as social goals (better health, better foods, housing, clothing, recycling, pesticides, It affects the economy of industrial nations (exports of chemical industry). *Handout IA: Chemistry, Principles, Paterns and applications, by Bruce Averill and Patricia Eldredge. Page 6

(pg4) Sc search for answers to questions and solutions to probls by using a procedure called the sc method. This procedure consists of making observations, formulating hypotheses, and designing exps, which lead in turn to additional observations, hypotheses, and exp in repeated cycles. Observations can be qualitative (describe prop or occurrences in a way that do not rely on number; ex crystalline sulfur is yellow, a penny dissolves is dilute nitric acid to form a blue sln and a brown gas) or quantitative observations (measurements - # and unit). After deciding to learn more about an observation or a set of observations, sc generally begin an investigation by forming a hypothesis, a tentative explanation for the observations. The hypothesis may not be correct, but it puts scs understranding of the syst being studied into a form that can be tested. For ex, the observation that we experience alternating pds of light and darkness corresponding to observed movements of the sun, moon, clouds, and shadows is consistent w either of two hyptheses: 1- Earth rotates on its axis every 24 hrs 2- the sun revolves around Earth every 24 hrs. Suitable exps can be designed to choose between these two alternatives. For the disappearance of the dinosaurs, the hypothesis was that the impact of a large extraterrestrial obj caused their extinction. Unfortunately this hypothesis is not amenable to direct testing by any ovbios exp, but scs can collect additional data that either support or refute it. After hypo formed, sc conduct exps to test its validity. Exp are systematic observations in which the variable of intest is clearly distinguished from any others. A properly designed and executed exp allow to determine if it is valid. Often exp demonstrate it is incorrect. More exp done, if a pt the sc may begin to think results are suffiently reproducible (that is, dependable) to merit being summarized in a law a verbal or math description of a phenomenon that allows for gen predictions. A law simply says what happens, it does not address the question of why. Theory attempts to explain why nature behaves as it does. The theory developed to explain the extinc of dinosaurs, for ex, is that Earth occsionally encounters small to med sized asteroids and that these encounters have unfortuante impliations for the continued existence of most species. This theory is by no means proven, but it is consistent with the bulk of the evidence amassed to date. *Law a gen statement of a relationship between the prop of liq and solid waterTheory a state that tries to explain the relationship between the T and the density of air based on fundamental principles. Quantitative observation measurements before and after

If I need more:1. Measured amounts of acid were addeed to a Rolaids tablet to see whether it really conusmues 48 times its weight in excess stomach acid. => experiment2. Heat always flows from hot obj to cooler ones, never in the other drection => law3. The universe was fromed by a massive explosion that propelled matter into a vacuum => theory4. Michael Jordan was the greates pure shooter ever to play prof basketball => hypothesis5. Limestone is relatively insoluble in water but dissolves readily in dilute acid with the evolution of a gas => qualitative observation6. Gas mx that contain more than 4% hydrogen in air are potentially explosive => quantitiative observation

*****Everything you see around you is formed from one or more of 114 presently known elements. AN element is a basic unit of matter: its a fundamental substance that cannot be decomposed into simpler substances by chemical or physical means114 are known at present. 92 occur in nature, 22 are synthetic. Not all are equally abundant: H is thought to account for ~75% of the mass in the universe; O and Si together ~75% of the earths crust; and O, C, and H make up more that 90% of the human body. By contrast, there is probably less than 20 g of Fr dispersed over the entire earth at any one time. Fr is an unstable radioactive element, atoms of which are continually being formed and destroyed in natl radiochem processes. Chemists refer to specific elements using a shorthand of one- or two- letter symbols. Many from the English name, other symbols derive from Latin or other languages (Na latin natrium; Pb latin plumbum, W german wolfram). Although only 92 elements occur natl, there are ovbiously far more thatn 92 diff kinds of matter on earth. Just look around, and youll surely find a few hundered. Compound - pure substances made up of two or more different elements chemically combined in constant or fixed proportionsIt can be broken down into elements by chemical processes*element- basic unit of matter: 111 are known at present. 92 occur in nature, 19 are syntheticcompound - pure substances that are made up of two or more elements chemically combined in constant or fixed proportions*Compound - pure substances made up of two or more different elements chemically combined in constant or fixed proportionsIt can be broken down into elements by chemical processes

A pure compound always contains the same elements in the same proportion or ratio by mass

A compound is written by giving its chemical formula, which lists the symbols of the individual constituent elements and indicates the # of atoms of each element with a subscript. If no subscript is given, the # 1 is understood.

Na + Cl2 NaCl mp 98 C -101 C 801CBp 883C -34

**Unlike chem comps, whose constituent units are identical, mx are simply blends of two or more substances added together in some random proportion without chemically changing the individual substances in the mixture.

Ex phys methods of separation: phase changes, distillation, filtration, centrifugation, *****Deciding whether an observed change is phys or chem can be tricky because in both cases there are changes in phys appearance. Water, for ex looks quite diff after it freezes, just as a car looks quite diff after it rusts. The freezing in water resutls from a change in how water moles are oriented relative to one another. This is a phys change because liq water and frozen water are both forms of water. The rusting of a car, by contrast is the result of the transformation of iorn to rust. This is a chem change because iron and rust are two diff materials, ea consisting of a diff arrangement of atoms. Iron is a element, rust is a compound consisting of iron and oxygen atoms. 2 powerful guidelins assist you in assessing phys and chem cahges. In a phys change, a cahnge in appearnace is the result of a new set of conditions imposed on the same matl. Restoring the original conditions restores the original appearance: frozen water melts upon warming. In a chem change, a change in appearnace is the result of the formation of a new matl that has its own unique set of phys prop. The more evidence you have suggesting that a diff matl has been formed, the greater the likelihood that the change is a chem change. Iron is a metal that can be used to build cars. Rust is not. This suggests that the rusting of iron is a chem change.

*Physical Property characteristic that can be observed or determined without changing the composition of the substanceEx.: color, hardness, electric conductivity, melting point, boiling point, tensile strength, density, state (solid, liquid, gas)Physical Change - change in the form of matter but not in its chemical identityUsually reversibleEx.: ______________________

Chemical Property - a characteristic of a material involving its chemical change Ex.: Iron reacts with oxygen to produce rustChemical Change - transformation of matter(s) into new kind of matter(s)Usually irreversible.New compounds are formedEx. Burning, cooking, rusting, souring of milk, ripening of fruit, browning of apples, taking a photograph, digesting food

******Accurate measurements are essential for the collection of scientific facts. The system of measurement used by most scientists is an updated metric plan called

Length meter, m 1 m = 3.281 ft = 39 inches

Mass kilogram, kg 1 kg = 2.205 lb

Volume m3 .946 L = 1 qt liter, L (1dm3), mL (cm3) 1 tsp = 5 m,L 2 tbs = 1 oz

Temperature K

*****Counting is usually exact: we can count exactly how many students are in this room. Measurements, on the other hand, are subject to error. Measurement is

Procedure in which a known quantity is compared with an unknown quantityconsists of a number and a unitIn chemistry measurements involve time, mass, volume, and distance among other things

subject to error: One source of error is the measuring instruments themselves. A thermometer, for ex, may consistently yield a result that is 2 C too low. Other error may result from the experimenters lack of skill or care in using measuring instruments.**************Convert 26 g to mgAns. = 26000 mgConvert 1250 L to LAns. = 0.00125 LConvert 165 cm to mAns. 1.65 mConvert 2720 Km to MmAns. = 2.72 Mm*******Concentration of mass. Its a measure of compactness, oh how tightly mas is squeezed into a given volume. A block of lead has much more mass squeezed into its vol than does a same-sized block of aluminum. The lead id therefore more dense. We think of density as the lightness or heaviness of obj of the same vol.

Ex. The aluminum. Think of it this way. Because lead is so dense, youneed only a little bit in order to have 1 kg. Al, by contrast, is far less dense, and so 1 kg of Al occupies much more vol that the same mass of lead.

Ex 2. Lead***