大学化学课件-国外原版教材-1.ppt

Copyright 1999, PRENTICE HALL,Chapter 1,1,Introduction: Matter and Measurement,Chapter 1,David P. White University of North Carolina, Wilmington,Copyright 1999, PRENTICE HALL,Chapter 1,2,The Study of Chemistry,The Molecular Perspective of Chemistry Matter is the physical material of the universe. Matter is made up of relatively few elements. On the microscopic level, matter consists of atoms and molecules. Atoms combine to form molecules. As we see, molecules may consist of the same type of atoms or different types of atoms.,Copyright 1999, PRENTICE HALL,Chapter 1,3,The Study of Chemistry,The Molecular Perspective of Chemistry In these models, we use red to represent oxygen, white to represent hydrogen, and gray to represent carbon.,Copyright 1999, PRENTICE HALL,Chapter 1,4,Classification of Matter,States of Matter Matter can be a gas, a liquid, or a solid. These are the three states of matter. Gases have no fixed shape or volume. Gases can be compressed to form liquids. Liquids have no shape, but they do have a volume. Solids are rigid and have a definite shape and volume.,Copyright 1999, PRENTICE HALL,Chapter 1,5,Classification of Matter,Pure Substances and Mixtures Atoms consist only of one type of element. Molecules can consist of more than one type of element. Molecules can have only one type of atom (an element). Molecules can have more than one type of atom (a compound). If more than one atom, element, or compound are found together, then the substance is a mixture.,Copyright 1999, PRENTICE HALL,Chapter 1,6,Pure Substances and Mixtures,Classification of Matter,Copyright 1999, PRENTICE HALL,Chapter 1,7,Pure Substances and Mixtures If matter is not uniform throughout, then it is a heterogeneous mixture. If matter is uniform throughout, it is homogeneous. If homogeneous matter can be separated by physical means, then the matter is a mixture. If homogeneous matter cannot be separated by physical means, then the matter is a pure substance. If a pure substance can be decomposed into something else, then the substance is a compound.,Classification of Matter,Copyright 1999, PRENTICE HALL,Chapter 1,8,Pure Substances and Mixtures If a pure substance cannot be decomposed into something else, then the substance is an element.,Classification of Matter,Copyright 1999, PRENTICE HALL,Chapter 1,9,Classification of Matter,Copyright 1999, PRENTICE HALL,Chapter 1,10,Classification of Matter,Separation of Mixtures Heterogeneous mixtures are not uniform throughout. Homogeneous mixtures can be separated by physical means (e.g., filtration, distillation or chromatography). Compounds can be decomposed into elements. Elements cannot be decomposed any further. Homogeneous liquid mixtures can be separated by distillation. Requires the different liquids to have different boiling points.,Copyright 1999, PRENTICE HALL,Chapter 1,11,Classification of Matter,Separation of Mixtures In essence, each component of the mixture is boiled and collected. The lowest boiling fraction is collected first.,Copyright 1999, PRENTICE HALL,Chapter 1,12,Classification of Matter,Separation of Mixtures,Copyright 1999, PRENTICE HALL,Chapter 1,13,Classification of Matter,Elements There are 114 elements known. Each element is given a unique chemical symbol (one or two letters). They are building blocks of matter. The earths crust consists of 5 main elements (shown next slide). The human body consists mostly of 3 main elements (O, C, and H).,Copyright 1999, PRENTICE HALL,Chapter 1,14,Elements,Classification of Matter,Copyright 1999, PRENTICE HALL,Chapter 1,15,Classification of Matter,Elements Chemical symbols with one letter have that letter capitalized (e.g., H, B, C, N, etc.) Chemical symbols with two letters have only the first letter capitalized (e.g., He, Be).,Copyright 1999, PRENTICE HALL,Chapter 1,16,Classification of Matter,Compounds Most elements interact to form compounds. The proportions of elements in compounds are the same irrespective of how the compound was formed. Law of Constant Composition (or Law of Definite Proportions): The composition of a pure compound is always the same. Therefore, if water is decomposed, then there will always be twice as much hydrogen gas formed as oxygen gas.,Copyright 1999, PRENTICE HALL,Chapter 1,17,Classification of Matter,Compounds If water is decomposed (shown here), then there will always be twice as much hydrogen gas formed as oxygen gas.,Copyright 1999, PRENTICE HALL,Chapter 1,18,Properties of Matter,Physical and Chemical Changes When a substance undergoes a physical change, its physical appearance changes. Example: the melting of ice (physical change) results in a solid being converted into a liquid. Physical changes do not result in a change of composition. When a substance changes its composition, it undergoes a chemical change: When pure hydrogen and pure oxygen react completely, they form pure water. In the flask containing water, there is no oxygen or hydrogen left over.,Copyright 1999, PRENTICE HALL,Chapter 1,19,Physical and Chemical Changes,Properties of Matter,Copyright 1999, PRENTICE HALL,Chapter 1,20,Units of Measurement,SI Units There are two types of units: fundamental (or base) units; derived units. There are 7 base units in the SI system. Derived units are obtained from the 7 base SI units. Example:,Copyright 1999, PRENTICE HALL,Chapter 1,21,SI Units,Units of Measurement,Copyright 1999, PRENTICE HALL,Chapter 1,22,Units of Measurement,SI Units Powers of ten are used for convenience with smaller or larger units in the SI system.,Copyright 1999, PRENTICE HALL,Chapter 1,23,Length and Mass Note the SI unit for length is the meter (m) whereas the SI unit for mass is the kilogram (kg). (1 kg weighs 2.2046 lb),Units of Measurement,Copyright 1999, PRENTICE HALL,Chapter 1,24,Units of Measurement,Temperature There are three temperature scales: Kelvin Scale Used in science. Same temperature increment as Celsius scale. Lowest temperature possible (absolute zero) is zero Kelvin. Absolute zero: 0 K = -273.15oC. Celsius Scale Also used in science. Water freezes at 0oC and boils at 100oC. To convert: K = oC + 273.15.,Copyright 1999, PRENTICE HALL,Chapter 1,25,Units of Measurement,Temperature Fahrenheit Scale Not generally used in science. Water freezes at 32oF and boils at 212oF. To convert:,Copyright 1999, PRENTICE HALL,Chapter 1,26,Units of Measurement,Temperature,Copyright 1999, PRENTICE HALL,Chapter 1,27,Units of Measurement,Volume The units for volume are given by (units of length)3. i.e., SI unit for volume is 1 m3. We usually use 1 mL = 1 cm3. Other volume units: 1 L = 1 dm3 = 1000 cm3 = 1000 mL.,Copyright 1999, PRENTICE HALL,Chapter 1,28,Units of Measurement,Density Used to characterize substances. Defined as mass divided by volume. Units: g/cm3. Originally based on mass (the density was defined as the mass of 1.00 g of pure water).,Copyright 1999, PRENTICE HALL,Chapter 1,29,Volume,Units of Measurement,Copyright 1999, PRENTICE HALL,Chapter 1,30,All scientific measures are subject to error. These errors are reflected in the number of figures reported for the measurement. These errors are also reflected in the observation that two successive measures of the same quantity are different.,Uncertainty in Measurement,Copyright 1999, PRENTICE HALL,Chapter 1,31,Precision and Accuracy Measurements that are close to the “correct” value are accurate. Measurements which are close to each other are precise. Measurements can be accurate and precise; precise but inaccurate; neither accurate nor precise.,Uncertainty in Measurement,Copyright 1999, PRENTICE HALL,Chapter 1,32,Precision and Accuracy,Uncertainty in Measurement,Copyright 1999, PRENTICE HALL,Chapter 1,33,Uncertainty in Measurement,Significant Figures The number of digits reported in a measurement reflect the accuracy of the measurement and the precision of the measuring device. All the figures known with certainty plus one extra figure are called significant figures. In any calculation, the results are reported to the fewest significant figures (for multiplication and division) or fewest decimal places (addition and subtraction).,Copyright 1999, PRENTICE HALL,Chapter 1,34,Uncertainty in Measurement,Significant Figures Non-zero numbers are always significant. Zeros between non-zero numbers are always significant. Zeros before the first non-zero digit are not significant. (Example: 0.0003 has one significant figure.) Zeros at the end of the number after a