Prentice Hall © 2003Chapter 1 Chapter 1 Introduction: Matter & Measurement CHEMISTRY The Central Science 9th Edition David P. White

Prentice Hall © 2003Chapter 1 Molecular Perspective of Chemistry Matter is anything that has mass and occupies space. Matter ultimately consists of atoms. Atoms are nature ’ s building blocks. Compounds may consist of the same type of atoms or different types of atoms. The Study of Chemistry

Prentice Hall © 2003Chapter 1 Why Study Chemistry? Chemistry is the study of the composition of matter and the changes that matter undergoes. Five general types of chemistry: organic, inorganic, biochemistry, analytical, and physical. CHEMISTRY STUDIES EVERYTHING!! The Study of Chemistry

Prentice Hall © 2003Chapter 1 Three States of Matter: Gas, liquid, or solid. Gases (vapors) have an indefinite shape, indefinite volume, and can be compressed. Liquids have an indefinite shape, but a definite volume. Liquids are not compressible. Solids are rigid, having a definite shape and volume. They are not compressible. Classification of Matter

Prentice Hall © 2003Chapter 1 Substances, Elements and Compounds: Substance: matter having distinct properties and the same composition from sample to sample. Substances can be classified as elements or compounds. Element: simplest form of matter that has a unique set of properties. Cannot be decomposed. Each element contains a unique kind of atom. Ex.: H or C Compound: a substance containing two or more elements chemically combined in a fixed proportion and structure. Ex.: NaCl Classification of Matter

Prentice Hall © 2003Chapter 1 Law of Constant Composition (c. 1800) Also called the Law of Definite Proportions. A given compound always contains exactly the same proportion of elements by mass regardless of the source of the compound. Example: A molecule of pure water (H 2 O) always is made up of two hydrogen atoms and one oxygen atom.

Prentice Hall © 2003Chapter 1 Pure Substances and Mixtures Mixtures: combinations of different substances. Composition of mixtures can vary from sample to sample. If matter is not uniform throughout, then it is a heterogeneous mixture. Ex.: vegetable soup If matter is uniform throughout, it is homogeneous. Ex.: air. Homogeneous mixtures are called solutions. Solutions can be gaseous, liquid, or solid! Classification of Matter

Prentice Hall © 2003Chapter 1 Mixtures, Substances, Compounds 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.

Prentice Hall © 2003Chapter 1 Elements If a pure substance cannot be decomposed into something else, then the substance is an element. Each element is given a unique chemical symbol (one or two letters). Elements are building blocks of matter. The main elements in the human body: CHNOPS! Classification of Matter

Prentice Hall © 2003Chapter 1 Physical properties can be measured without changing the identity and composition of a substance. Ex.: color, density, m.p. Intensive properties do not depend on the amount of substance. Ex.: m.p., b.p., density Extensive properties depend on the amount of substance present. Ex.: mass, volume Chemical properties describe how a substance reacts to form other substances. Ex: flammability Properties of Matter Types of properties

Prentice Hall © 2003Chapter 1 Physical and Chemical Changes When a substance undergoes a physical change, its physical appearance changes, not its composition! Ex. Changes of state (ice melting) When a substance changes its composition, it undergoes a chemical change. Chemical changes = chemical reactions Ex.: solid iron + gaseous oxygen form solid iron oxide Changes of Matter

Prentice Hall © 2003Chapter 1 Physical and Chemical Changes Properties of Matter

Prentice Hall © 2003Chapter 1 Four Clues to Chemical Changes Transfer of energy Change in color Production of gas Formation of a precipitate: solid that forms or settles out from a liquid mixture. But…even with a clue, you cannot be sure of a chemical change! You need to test the composition of the sample before and after to be sure! Chemical Changes

Prentice Hall © 2003Chapter 1 Separation of Mixtures Mixtures can be separated if their physical properties are different. Separation is based on differences in physical properties. Separation by filtration, distillation, chromatography, etc. Properties of Matter

Prentice Hall © 2003Chapter 1 Separation of Mixtures Homogeneous liquid mixtures can be separated by distillation. Distillation requires the different liquids to have different boiling points. In essence, each component of the mixture is boiled and collected. The lowest boiling fraction is collected first. Properties of Matter

Separation of Mixtures

Prentice Hall © 2003Chapter 1 Separation of Mixtures Chromatography separates mixtures that have different abilities to adhere to solid surfaces. The greater the affinity the component has for the surface (paper) the slower it moves. The greater affinity the component has for the liquid, the faster it moves. Chromatography can be used to separate the different colors of inks in a pen. Properties of Matter

Prentice Hall © 2003Chapter 1 SI Units (Système International d’Unités) There are two types of units: –fundamental (or base) units; –derived units. Units of Measurement

Prentice Hall © 2003Chapter 1 Units of Measurement

Prentice Hall © 2003Chapter 1 Prefixes in the Metric System Units of Measurement

Prentice Hall © 2003Chapter 1 Derived Units Derived units are obtained from base SI units. Example: Units of Measurement

Prentice Hall © 2003Chapter 1 Temperature There are three temperature scales: Kelvin Scale (Absolute Scale) –Used in science. –Same temperature increment as Celsius scale. –Lowest temperature possible = absolute zero –Absolute zero: 0 K =  o C. Units of Measurement

Prentice Hall © 2003Chapter 1 Temperature Celsius Scale –Water freezes at 0 o C and boils at 100 o C. –To convert: K = o C Fahrenheit Scale _ Water freezes at 32 o F and boils at 212 o F. –To convert: Units of Measurement

Temperature Units of Measurement

Prentice Hall © 2003Chapter 1 Density Used to identify substances. Units: g/cm 3 or g/mL Density is an intensive property. Density is temperature dependent. Why? Water is different! Units of Measurement

Prentice Hall © 2003Chapter 1 Exact and Inexact Numbers Two kinds of numbers are used in science. Exact numbers: values are known exactly; values are infinitely precise. Ex: definitions (12 inches = 1 foot), the number 1 in conversion factors, counting numbers Inexact numbers: values have uncertainty. Ex: all measurements (12.34 cm)

Prentice Hall © 2003Chapter 1 Uncertainty in Measurement All scientific measures are subject to error. These errors are reflected in the number of figures reported for the measurement. Precision and Accuracy Measurements that are close to the “ correct ” value are accurate. Measurements that are close to each other are precise. Uncertainty in Measurement

Prentice Hall © 2003Chapter 1 Precision and Accuracy Uncertainty in Measurement

Prentice Hall © 2003Chapter 1 Significant Figures Number of digits reported in a measurement reflect the accuracy of the measurement and the precision of the measuring device. Significant figures: all the figures known with certainty plus one extra figure. Uncertainty in Measurement

Prentice Hall © 2003Chapter 1 Significant Figures Rules 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: has one significant figure.) Zeros at the end of the number after a decimal point are significant. Zeros at the end of a number with no decimal point are ambiguous (e.g. 10,300 g). Use scientific notation or a decimal to indicate number of significant figures. Uncertainty in Measurement

Prentice Hall © 2003Chapter 1 Significant Figures Multiplication & Division: report answer to the smallest number of significant figures in the calculation. Addition & Subtraction: report answer to the smallest number of decimal places in the calculation. Uncertainty in Measurement