Honors Chemistry I 84.135

Honors Honors Chemistry IChemistry I

84.13584.135Dr. Nancy De LucaDr. Nancy De Luca

Course web site:Course web site:http://faculty.uml.edu/ndeluca/84.135

http://faculty.uml.edu/ndeluca/84.135

http://faculty.uml.edu/ndeluca/84.135

MatterMatterMatter is anything that has Matter is anything that has

mass and occupies space. It mass and occupies space. It includes everything around us, includes everything around us, including the air that we breath, our including the air that we breath, our skin and bones, and the earth skin and bones, and the earth underneath us.underneath us.

Properties of MatterProperties of MatterMatter can be described by its Matter can be described by its physicalphysical or or chemicalchemical properties.properties.

Physical propertiesPhysical properties are a description are a description of the substance, and include mass, of the substance, and include mass, color, physical state (solid, liquid or color, physical state (solid, liquid or gas) at a specific temperature, gas) at a specific temperature, density, melting or boiling point, odor, density, melting or boiling point, odor, solubility, etc.solubility, etc.

Properties of MatterProperties of Matter

mercury

iodine

mercury(II)iodide

Mercury, a Mercury, a metal that is a metal that is a liquid at room liquid at room temperature, temperature, reacts with reacts with iodine, a black iodine, a black shiny solid, to shiny solid, to produce produce mercury (II) mercury (II) iodide, a red iodide, a red crystalline solid.crystalline solid.

Properties of MatterProperties of Matter During a During a physical changephysical change, the , the

chemical identity of the substance or chemical identity of the substance or substances does not change.substances does not change.

Examples of physical changes Examples of physical changes include evaporation, filtration, and include evaporation, filtration, and changes of state. changes of state.

Properties of MatterProperties of MatterWhen ice is melted and the liquid is When ice is melted and the liquid is then evaporated, all three forms of then evaporated, all three forms of water are chemically the same, Hwater are chemically the same, H22O.O.

When salt water is boiled, the salt When salt water is boiled, the salt remains, and the water is removed as remains, and the water is removed as water vapor.water vapor.

For either process, there is no change For either process, there is no change in the identity of the substances. This in the identity of the substances. This is true for all physical changes.is true for all physical changes.

Physical ChangesPhysical ChangesWhen

water boils, its chemical composition remains the same. The molecules are now farther apart.

Physical ChangePhysical Change

The dissolving of sugar in water is a physical The dissolving of sugar in water is a physical change. The chemical identity of the water change. The chemical identity of the water and the sugar remain unchanged.and the sugar remain unchanged.

FiltrationFiltrationDuring During

filtration,filtration, liquids liquids are separated from are separated from solids solids by physical by physical meansmeans. The liquid . The liquid and solid maintain and solid maintain their chemical their chemical identity.identity.

DistillationDistillation During distillation, liquids may be separated from other liquids, or from solids. The chemical identity of each component remains unchanged.

Properties of MatterProperties of MatterChemical properties Chemical properties are are

descriptions of how a substance descriptions of how a substance reacts chemically. Examples include reacts chemically. Examples include the rusting of iron in the presence of the rusting of iron in the presence of air and water, the souring of milk, or air and water, the souring of milk, or the burning of paper to form carbon the burning of paper to form carbon dioxide and water vapor.dioxide and water vapor.

Chemical ChangesChemical Changes As iron rusts, As iron rusts, the iron atoms the iron atoms combine with combine with oxygen in the air oxygen in the air to form a new to form a new substance, rust, substance, rust, or iron (III) or iron (III) oxide.oxide.

Chemical ChangesChemical ChangesDuring a chemical change, atoms During a chemical change, atoms rearrange the way they are attached to rearrange the way they are attached to each other, forming new substances with each other, forming new substances with properties that are often quite different properties that are often quite different from the starting materials.from the starting materials.

Intensive & Extensive Intensive & Extensive PropertiesProperties

IntensiveIntensive properties do not depend properties do not depend on the amount or quantity of matter. on the amount or quantity of matter. Melting point, chemical formula and Melting point, chemical formula and color are intensive properties.color are intensive properties.Extensive Extensive properties depend upon properties depend upon the quantity of matter or sample size. the quantity of matter or sample size. Examples include length, mass and Examples include length, mass and volume.volume.

The ElementsThe ElementsAll matter is composed of All matter is composed of

approximately 100 elements, in approximately 100 elements, in various combinations, listed on the various combinations, listed on the periodic table. periodic table.

The table groups elements with The table groups elements with similar chemical and physical similar chemical and physical properties.properties.

The Periodic TableThe Periodic Table Periodic tables group elements with Periodic tables group elements with

similar properties in vertical similar properties in vertical groupsgroups or or familiesfamilies..

Metals are on the left side of the table, Metals are on the left side of the table, and non-metals are on the right.and non-metals are on the right.

A bold line resembling a flight of stairs A bold line resembling a flight of stairs usually separated metals from non-usually separated metals from non-metals.metals.

The Periodic TableThe Periodic Table

metal/non-metal line

MeasurementsMeasurementsScientists needed to establish a system Scientists needed to establish a system of measurement and units before they of measurement and units before they could reproduce or communicate the could reproduce or communicate the results of their experiments.results of their experiments.

The Metric System is used, with the The Metric System is used, with the units of grams (for mass) and units of grams (for mass) and milliliters (for volume) commonly used milliliters (for volume) commonly used in the chemistry laboratory.in the chemistry laboratory.

MeasurementsMeasurementsPrefixes Commonly used in Chemistry:Prefixes Commonly used in Chemistry:

prefix nameprefix namesymbolsymbol value value exponential notationexponential notation

kilo kilo k k 1,000 1,000 101033

centicenti c c 1/100 or .01 1/100 or .01 1010-2-2

millimilli m m 1/1,000 or .001 101/1,000 or .001 10-3-3

micromicro µ µ .000001 .000001 1010-6-6

nanonano n n 1010-9-9

picopico p p 1010-12-12

Measurements- UnitsMeasurements- Units SI or SI or International SystemInternational System units are units are

used.used.QuantityQuantity UnitUnit SymbolSymbolMassMass kilogramkilogram kg kgLengthLength metermeter m mTimeTime secondsecond s sTemperatureTemperature kelvinkelvin K K

Measurement- VolumeMeasurement- VolumeVolume is a derived unit. A liter Volume is a derived unit. A liter

is a volume that is 10cm x 10cm x is a volume that is 10cm x 10cm x 10cm, or 1000 cm10cm, or 1000 cm33. . Therefore, a milliliter (mL) is the Therefore, a milliliter (mL) is the same as a cubic centimeter (cmsame as a cubic centimeter (cm33 or or cc).cc).

Measurement - Measurement - TemperatureTemperature

In the chemistry lab, In the chemistry lab, temperature is temperature is measured in degrees measured in degrees Celsius or Centigrade. Celsius or Centigrade. The temperature in The temperature in Kelvins is found by Kelvins is found by adding 273.15 adding 273.15

The Fahrenheit scale The Fahrenheit scale has 180 has 180 ooF/100 F/100 ooC. C. This is reason for the This is reason for the 5/9 or 9/5 in the 5/9 or 9/5 in the conversion formulas.conversion formulas.

Measurement - UnitsMeasurement - UnitsCommon English-Metric Conversion Common English-Metric Conversion

FactorsFactors

2.54 cm = 1 inch2.54 cm = 1 inch1 lb = 453.6 g1 lb = 453.6 g1 qt = 943 mL1 qt = 943 mL

Significant FiguresSignificant FiguresWhen writing a number, the certainty When writing a number, the certainty with which the number is known should with which the number is known should be reflected in the way it is written.be reflected in the way it is written.

Digits which are the result of Digits which are the result of measurement or are known with a measurement or are known with a degree of certainty are called degree of certainty are called significant digits or significant figuressignificant digits or significant figures..

Significant FiguresSignificant FiguresThe goal of paying attention to The goal of paying attention to significant figures is to make sure that significant figures is to make sure that every number accurately reflects the every number accurately reflects the degree of certainty to which it is known.degree of certainty to which it is known.Likewise, when calculations are Likewise, when calculations are performed, the final result should reflect performed, the final result should reflect the same degree of certainty as the the same degree of certainty as the least least certaincertain quantity in the calculation. quantity in the calculation.

Significant FiguresSignificant FiguresIf someone says “There are If someone says “There are

roughly a hundred students enrolled roughly a hundred students enrolled in the freshman chemistry course,” in the freshman chemistry course,” the enrollment should be written as the enrollment should be written as 100100 or or 1 x 101 x 1022. .

Either notation indicates that Either notation indicates that the number is approximate, with the number is approximate, with only one significant figure.only one significant figure.

Significant FiguresSignificant FiguresIf the enrollment is exactly one If the enrollment is exactly one

hundred students, the number hundred students, the number should be written with a decimal should be written with a decimal point, as point, as 100.100. , or , or 1.00 x 101.00 x 1022..

Note that in either form, the Note that in either form, the number has three significant figures.number has three significant figures.

Significant FiguresSignificant FiguresThe rules for counting significant The rules for counting significant

figures:figures:

1. Any non-zero integer is a 1. Any non-zero integer is a significant figure.significant figure.

Significant FiguresSignificant Figures2. Zeros 2. Zeros maymay be significant, depending be significant, depending

upon where they appear in a number.upon where they appear in a number.

a) Leading zeros (one that precede a) Leading zeros (one that precede any non-zero digits) are any non-zero digits) are not not significant.significant.For example, in 0.02080, the first two For example, in 0.02080, the first two zeros are not significant. They only zeros are not significant. They only serve to place the decimal point.serve to place the decimal point.

Significant Figures – Zeros Significant Figures – Zeros (cont’d)(cont’d)

b) Zeros between non-zero integers are b) Zeros between non-zero integers are always significant.always significant. In the number In the number 0.02080, the zero between the 2 and the 8 0.02080, the zero between the 2 and the 8 is a significant digit.is a significant digit.

c) Zeros at the right end of a number are c) Zeros at the right end of a number are significant only if the number contains a significant only if the number contains a decimal point. In the number 0.02080, the decimal point. In the number 0.02080, the last zero is the result of a measurement, last zero is the result of a measurement, and and is significant.is significant.

Significant FiguresSignificant FiguresThus, the number 0.02080 has Thus, the number 0.02080 has

four significant figures. four significant figures.

If written in scientific notation, If written in scientific notation, all significant digits must appear. all significant digits must appear. So 0.02080 becomes So 0.02080 becomes 2.080 x 102.080 x 10-2-2..

Significant FiguresSignificant Figures3. Exact numbers have an unlimited 3. Exact numbers have an unlimited

number of significant figures. Examples number of significant figures. Examples are 100cm = 1m, the “2” in the formula are 100cm = 1m, the “2” in the formula 22ππr, or the number of atoms of a given r, or the number of atoms of a given element in the formula of a compound, element in the formula of a compound, such as the “2” in Hsuch as the “2” in H22O.O.

Using an exact number in a calculation Using an exact number in a calculation will not limit the number of significant will not limit the number of significant figures in the final result.figures in the final result.

Significant Figures - Significant Figures - CalculationsCalculations

When calculations are performed, the When calculations are performed, the final result should reflect the same final result should reflect the same degree of certainty as the degree of certainty as the least certainleast certain quantity in the calculation.quantity in the calculation.

That is, the least certain quantity will That is, the least certain quantity will influence the degree of certainty in the influence the degree of certainty in the final result of the calculation. final result of the calculation.


There are two sets of rules when performing There are two sets of rules when performing calculations. One for addition and calculations. One for addition and subtraction, and the other for multiplication subtraction, and the other for multiplication and division.and division.

For Multiplication and DivisionFor Multiplication and Division::The result of the calculation should have the The result of the calculation should have the same number of significant figures as the same number of significant figures as the least preciseleast precise measurement used in the measurement used in the calculation.calculation.


Multiplication & DivisionMultiplication & Division::Example: Determine the density of Example: Determine the density of an object with a volume of 5.70 cman object with a volume of 5.70 cm33 and a mass of 8.9076 grams.and a mass of 8.9076 grams.


Multiplication & DivisionMultiplication & Division::Example: Determine the density of Example: Determine the density of an object with a volume of 5.70 cman object with a volume of 5.70 cm33 and a mass of 8.9076 grams.and a mass of 8.9076 grams.

δδ = mass/volume = 8.9076 g/5.70 cm = mass/volume = 8.9076 g/5.70 cm33

δδ = 1.5627368 = 1.56 g/cm = 1.5627368 = 1.56 g/cm33


Addition and SubtractionAddition and Subtraction::The result has the same number of The result has the same number of places after the decimal as the places after the decimal as the least least preciseprecise measurement in the calculation. measurement in the calculation.

For example, calculate the sum of:For example, calculate the sum of:10.011g + 5.30g + 9.7093g = 25.0203 10.011g + 5.30g + 9.7093g = 25.0203 = 25.02g= 25.02g

Significant Figures - Significant Figures - MeasurementMeasurement

All measurements involve some degree All measurements involve some degree of uncertainty. When reading a mass of uncertainty. When reading a mass from a digital analytical balance, the last from a digital analytical balance, the last digit (usually one-ten thousandth of a digit (usually one-ten thousandth of a gram) is understood to be uncertain.gram) is understood to be uncertain.

When using other devices in the When using other devices in the laboratory, such as a ruler, graduated laboratory, such as a ruler, graduated cylinder, buret, etc., you should cylinder, buret, etc., you should estimate estimate one place beyondone place beyond the smallest divisions the smallest divisions on the device.on the device.

Significant Figures - Significant Figures - MeasurementsMeasurements

The volume should be The volume should be estimated to the estimated to the nearest hundredth of a nearest hundredth of a milliliter, since the milliliter, since the buret is marked in buret is marked in tenths of a milliliter.tenths of a milliliter.

The correct reading is The correct reading is 20.15 (or 20.14 or 20.15 (or 20.14 or 20.16) mL. It is 20.16) mL. It is understood that the understood that the last number is last number is uncertain.uncertain.

Significant Figures - Significant Figures - MeasurementsMeasurements

The value of 20.15 The value of 20.15 mL indicates a mL indicates a volume in between volume in between 20.1 mL and 20.2 20.1 mL and 20.2 mL. mL.

If the liquid level If the liquid level were resting right on were resting right on one of the divisions, one of the divisions, the reading should the reading should reflect this by ending reflect this by ending in a zero. in a zero.

Conversion of UnitsConversion of UnitsMany chemical calculations involve the Many chemical calculations involve the conversion of units. An example is conversion of units. An example is calculating how many grams of a product calculating how many grams of a product can be obtained from a given mass of a can be obtained from a given mass of a reactant. The calculation involves going reactant. The calculation involves going from mass of reactant to moles of from mass of reactant to moles of reactant to moles of product to grams of reactant to moles of product to grams of product. You should write in your unites product. You should write in your unites for all calculations, and make sure they for all calculations, and make sure they cancel properly.cancel properly.

Metric Conversion Metric Conversion FactorsFactors

These conversion factors are These conversion factors are useful and worth learning.useful and worth learning.

I inch = 2.54 cmI inch = 2.54 cm1 lb = 454.6 g1 lb = 454.6 g

1 L = 1.0567 qt1 L = 1.0567 qt

ProblemProblemThe density of mercury is 13.6 The density of mercury is 13.6

g/mL. What is the weight, in lbs, of g/mL. What is the weight, in lbs, of a quart of mercury?a quart of mercury?

Accuracy & PrecisionAccuracy & PrecisionMost experiments are Most experiments are

performed several times to help performed several times to help ensure that the results are ensure that the results are meaningful. A single experiment meaningful. A single experiment might provide an erroneous result if might provide an erroneous result if there is an equipment failure or if a there is an equipment failure or if a sample is contaminated. By sample is contaminated. By performing several trials, the results performing several trials, the results may be more reliable.may be more reliable.

Accuracy & PrecisionAccuracy & PrecisionIf the experimental values are close to If the experimental values are close to the actual value (if it is known), the the actual value (if it is known), the data is said to be data is said to be accurate. accurate. If the experimental values are all very If the experimental values are all very similar and reproducible, the data is similar and reproducible, the data is said to be said to be preciseprecise..The goal in making scientific The goal in making scientific measurements is to that the data be measurements is to that the data be both accurate and precise.both accurate and precise.

Accuracy & PrecisionAccuracy & PrecisionData can be precise, but inaccurate. Data can be precise, but inaccurate. If a faulty piece of equipment or a If a faulty piece of equipment or a contaminated sample is used for all contaminated sample is used for all trials, the data may be in agreement trials, the data may be in agreement (precise), but inaccurate. Such an (precise), but inaccurate. Such an error is called a error is called a systematic errorsystematic error. If . If the scientist has good technique, the the scientist has good technique, the results will be similar, but too high or results will be similar, but too high or too low due to the systematic error.too low due to the systematic error.

Random ErrorRandom ErrorIn many experiments, data varies a bit In many experiments, data varies a bit with each trial. The variation in the with each trial. The variation in the results is due to results is due to random errorrandom error. . Examples might be estimating the last Examples might be estimating the last digit for the volume in a buret. Random digit for the volume in a buret. Random errors have an equal probability of errors have an equal probability of being too high or too low. As a result, if being too high or too low. As a result, if enough trials are performed, the enough trials are performed, the random error will average itself out.random error will average itself out.

Random and Systematic Random and Systematic ErrorsErrors

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Honors Chemistry I 84.135