# Chapter 1 Introduction to Chemistry

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Chapter 1 Introduction to Chemistry. What is Science?. Natural abilities are like natural plants; they need pruning by study. Sir Francis Bacon (1561-1626). The Nature of Science and Chemistry. Definitions Science: knowledge Sir Francis Bacon: And thus knowledge itself is power - PowerPoint PPT PresentationTRANSCRIPT

What is Science?Natural abilities are like natural plants; they need pruning by study. Sir Francis Bacon (1561-1626) DefinitionsScience: knowledgeSir Francis Bacon: And thus knowledge itself is powerModern science, the acquisition of knowledge, is acquired by experience (experiment)Chemistry: the study of matter and its interactions with other matter and with energy.The Nature of Science and ChemistryChemistry and the Natural SciencesScientific method: investigations that are guided by theory and earlier experiments.Hypothesis: a possible explanation for an event.Law: a statement that summarizes a large number of observations.Theory: an explanation of the laws of nature.The Scientific MethodMatter: anything that has mass and occupies space.Mass: the quantity of matter in an object.Weight: the force of attraction between an object and other objects.MatterMass on moon and earth is the same.Weight on moon and earth is the different.Mass and WeightProperty: anything observed or measured about a sample of matter.Extensive property: depends on the size of the sample.mass, volumeIntensive property: independent of sample size.density, color, melting or boiling pointProperties of MatterPhysical properties: can be measured without changing the composition of the sample.mass, density, color, melting pointPhysical change: a change that occurs without changing the composition of the material.freezing, meltingPhysical Properties and ChangesChemical properties: describe the reactivity of a material.Natural gas burns in air; iron rusts.Chemical change: at least part of the material is changed into a different kind of matter.The digestion of sugar is a chemical change.Chemical PropertiesPracticeState if the underlined property or changes is intensive or extensive and chemical or physical.The color of mercury is silvery.The sample of iron rusts by reaction with oxygen.The heat released by burning coal can power a city.Water boils at 100C.A new pencil is 10 inches long.Substances - a material that is chemically the same throughout.Two types of substancesElements cannot be broken into simpler substances.Compounds can be broken down into elements.Classification of MatterSubstance: cannot be separated into component parts by physical methods.Compound: a substance which can be separated into simpler substances by chemical methods.Element: a substance which cannot be separated into simpler substances by chemical methods.SubstancesMixture: matter that can be separated into simpler materials by physical methods.Heterogeneous mixture: composition of the mixture changes from one part to another.Homogeneous mixture or solution: composition of the mixture is uniform throughout.Alloy: a solution of a metal and another material (usually another metal).MixturesClassification of MatterPracticeIdentify the following types of matter as elements, compounds, heterogeneous mixtures, or homogeneous mixtures.Sodium chlorideStainless steelChlorinesoilMeasurementMost modern science depends on measurementsParts of a measurementThe object of the measurementThe value of the measurementThe units of the measurementThe reliability of the measurementExample The mass of iron was 4.0501 gramsAll parts MUST be present in an answer for complete credit!!Modern chemistry is largely based on experimental measurements. The confidence in measurements involves:Accuracy: agreement of a measurement with the true value.Precision: agreement among repeated measurements of the same quantity. Accuracy and Precisionaccurate and preciseprecise but not accurateaccurate but not preciseneither accurate nor preciseAccuracy and PrecisionAccuracy and PrecisionThe number of significant figures is the number of digits from the first non-zero digit through the last reported digit.The uncertainty is at least 1 unit in the last reported digit.Leading zeros zeros preceding the first non-zero digit are NEVER significant. Trailing zeros a decimal point is the key.No decimal trailing zeros are NOT significantDecimal trailing zeros ARE significantSignificant FiguresQuantities that are not limited by significant figures:counted numbers or tallies.defined numbers.the power of ten in exponential notation.Significant FiguresHow many significant figures are present in each of the measured quantities?0.0012 106 2006 900.0 1.0012 0.001060Significant FiguresSince trailing zeros in numbers without a decimal points may be confusing for significant figures use scientific notation.1001? Or should there have been a decimal? 1 x 1021 1.0 x 1022 1.00 x 1023 Significant FiguresDetermine the number of significant figures:100.100.0 30505437,000 125,904,0004.80 x 10-3 4.800 x 10-30.0048PracticeThe absolute uncertainty can be no smaller than the least accurate number. 12.02 - 10.4 1.62 1.6 The answer should have no more decimal places than the least accurate number.Uncertainty in Addition and SubtractionAnswers should have no more significant figures than the least accurate number. 3121 x 12 = 37452 = 3.7 x 104 # sig. digits 4 x = = NOT 37!!!!!!37000 is questionable222Uncertainty in Multiplication and DivisionDetermine accuracy in the same order as the mathematical operations, # of significant digits are in red. density = 3.7 g/mLBe mindful of what your calculator gives you!!32Mixed OperationsRoundingBe cautious about rounding during multiple steps.Keep more significant figures than you need in intermediate steps.Ex:2.5 x 4.50 x 11.25 = ?Evaluate each expression to the correct number of significant figures. (a) 4.184 x 100.620 x (25.27 - 24.16) (b) (c) PracticeCalculate each to the correct number of significant figures . a) 0.1654 + 2.07 - 2.114 b) 8.27 x (4.987 - 4.962) c) d) 9.5 + 4.1 + 2.8 + 3.1754(4 is exact)PracticeQuantity Unit AbbreviationLength metermMass kilogramkgTime secondsTemperature kelvinKAmount mole molElectric current ampereALuminous intensity candelacdBase Units in the SIPrefixAbbreviationMeaningmega-M106kilo-k103centi-c10-2milli-m10-3micro-m10-6nano-n10-9pico-p 10-12Common Prefixes Used With SI Units1 kilogram is equal to 1000 g.Prefixes Used With SI UnitsUnit conversion factor: a fraction in which the numerator is a quantity equal or equivalent to the quantity in the denominator, but expressed in different unitsThe relationship 1 kg = 1000 gGenerates two unit conversion factors:Unit Conversion FactorsUnit ConversionsLets convert 5.73 g to kg.Start with what you know!!!Add conversion factors to cancel unitsUnits must be same on top & bottom to cancelgrams on topgrams on bottom0.00573 kgPracticeConvert the following:17.43 km to cm165 g to kgVolume is the product of three lengths.The standard unit of volume is the cubic meter (m3). 100 cm = 1 m (100 cm)3 = (1 m)3 106 cm3 = 1 m3Two important non-SI units of volume are the liter and milliliter. 1 liter (L) = 1000 mL = 1000 cm3 1 mL = 1 cm3 Conversion Among Derived UnitsVolumes can be expressed in different units depending on the size of the object.1 m3 contains1000 L1 L contains1000 mLVolumeExpress a volume of 1.250 L in mL, cm3, and m3 Using Unit ConversionsDensity: mass per unit volume Density, in SI base units, is kg/m3 (kg m-3).Most commonly used density units are g/cm3 (g cm-3 or g/mL) for solids and liquids, and g/L for gases.DensityThe density of Ti is 4.50 g/cm3 or 4.50 g = 1 cm3.Calculate the volume of 7.20 g Ti. Conversions Between Equivalent UnitsEnglish SystemPracticeExpress 323 milliliters in gallons.Express 3.61 cubic feet in cubic centimeters. 0 Kelvin 273 373-273o Celsius 0o 100o-460o Fahrenheit 32o 212oFor waterTemperature Conversion FactorsExpress 17.5C in F and in K.PracticePracticeIt has been estimated that 1.0 g of seawater contains 4.0 pg of Au. The total mass of seawater in the oceans is 1.6x1012 Tg, If all of the gold in the oceans were extracted and spread evenly across the state of Georgia, which has a land area of 58,910 mile2, how tall, in feet, would the pile of Au be?Density of Au is 19.3 g/cm3. 1.0 Tg = 1012g. PracticeOne metal object is a cube with edges of 3.00 cm and a mass of 140.4 g. A second metal object is a sphere with radius 1.42 cm and a mass of 61.6 g. Are these objects made of the same or different metals? Assume the calculated densities are accurate to 1.00%.PracticeA 40-lb container of peat moss measures 14 x 20 x 30 in. A 40-lb container of topsoil has a volume fo 1.9 gal. Calculate the density of both the peat moss and the topsoil.How many bags of peat moss are needed to cover an area measuring 10 ft x 20 ft x 2 in?PracticeOn a typical day, a hurricane expends the energy equivalent to the explosion of two thermonuclear weapons. A thermonuclear weapon has the explosive power of 1.0 Mton of nitroglycerin. Nitroglycerin generates 7.3 kJ of explosive power per gram of nitroglycerin. The hurricanes energy comes from the evaporation of water that requires 2.3 kJ per gram of water evaporated. How many gallons of water does a hurricane evaporate per day?THINK!!Homework:OWL: All of the required assignmentsbook: All questions from the end of the chapter are recommended as practice.