Chapter 1 Introduction: Matter and Measurement Honors Chemistry Lecture Notes 1.1 The Study of Chemistry: The study of and the it undergoes. Matter: Anything that has and takes up The Atomic and Molecular Perspective of Chemistry A is any characteristic that allows us to recognize a particular type of matter and to distinguish it from other types. As we proceed through this course, we will relate the properties of matter to its, that is, to the particular elements it contains. Matter are the building blocks of matter. Matter Atoms are the building blocks of matter. Each is made of the same kind of atom. A is made of two or more different kinds of elements. Chemistry Chemistry is the science that seeks to understand the and of matter by studying the and of matter of atoms and molecules. Give It Some Thought: Practice Question a. In round numbers, about how many elements are there? (Circle One) 1. about 1000 elements 2. about 100 elements 3. about 50 elements 4. about 200 elements b. What submicroscopic particles are the building blocks of matter? (Circle One) 1. atoms and molecules 2. cells 3. microcrystals 4. metals and nonmetals Why Study Chemistry? Chemistry provides important understanding of our world and how it works. Chemistry impacts our daily lives. o Improvement of health care with o Conservation of o Protection of the 1
Why Study Chemistry? o Provision of our everyday needs for o We have increased food production through the development of o We have developed and other materials that are used in almost every facet of our lives. Why Study Chemistry? o You will learn to use the powerful language and ideas that have evolved to describe and enhance our understanding of. o Chemistry truly is the, tying together the fields of biology, engineering, agriculture, geology, etc. The Language of Chemistry o Is universal! o An understanding of the behavior of atoms and molecules provides powerful insights in other areas of modern. o Chemistry will probably play a significant role in your future. o You will be better prepared for the future if you increase your understanding of chemical principles. 1.2 Classification of Matter o Two principal ways of classifying matter are 1. According to its physical state 2. According to its composition. States of Matter o Gas (vapor) o No fixed o Conforms to the volume and shape of its container. o Can be to occupy a smaller volume, or it can to occupy a larger one. States of Matter o Liquid o independent of its container but has no specific shape o Assumes of the portion of the container that it occupies States of Matter o Solid o Has both a o Neither liquids nor solids can be compressed to any appreciable extent. Molecular Level of Gases o Gas molecules are and moving at high speeds, colliding repeatedly with each other and with the walls of the container. Molecular Level of Liquids o Liquid molecules are, but still move rapidly, allowing them so slide over each other. o Liquids flow easily. 2
Molecular Level of Solids o In a solid, molecules are held tightly together, usually in, in which the molecules can wiggle only slightly in their otherwise fixed positions. Composition of Matter o A pure substance is matter that has and a composition that doesn t vary from sample to sample. o Pure substances are either Pure Substances o cannot be decomposed into simpler substances. o On the molecular level, each element is composed of only one kind of atom. o substances composed of two or more elements chemically bonded together, so they contain two or more kinds of atoms. Mixtures o Combinations of two or more substances in which each substance retains its own chemical identity. o. Elements o We use to denote the 116 known elements. o The has arranged all of the elements into groups and columns according to their similarities. o We will need to become familiar with all of the symbols for the elements, but you will always be allowed the use of a periodic table! Question: o What is the elemental symbol for sodium? (Circle One) 1. S 2. Na 3. Sn 4. Sm 5. Sr Compounds o Most elements interact with other elements to form compounds. o The properties of compounds are than the elements that make them up. Law of constant composition o The elemental composition of a pure compound. o A pure compound will have the same composition regardless if it was made in the lab, or found in nature. Mixtures o Mixtures two or more substances blended together and appears uniform throughout in composition, even at a microscopic level. Also known as. o Mixtures two or more substances blended together and appears different throughout, even at the microscopic level. 3
Classification of Matter (Draw the flow chart with me) Sample Exercise: Distinguishing among Elements, Compounds, and Mixtures White gold, used in jewelry, contains two elements, gold and palladium. Two different samples of white gold differ in the relative amounts of gold and palladium that they contain. Both are uniform in composition throughout. Without knowing any more about the materials, use the figure above to characterize and classify white gold. Answer PRACTICE EXERCISE Aspirin is composed of 60.0% carbon, 4.5% hydrogen, and 35.5% oxygen by mass, regardless of its source. Use Figure 1.9 to characterize and classify aspirin. Answer: 1.3 Properties and Changes of Matter o Every substance has a unique set of properties. o Properties can be categorized as. o Properties can also be classified as. Properties of Matter o Physical Properties: o Can be observed without changing a substance into another substance. o. 4
o Chemical Properties: o Can only be observed when a substance is changed into another substance. o Properties of Matter o Intensive Properties: o Independent of the amount of the substance that is present. o. o Extensive Properties: o Dependent upon the amount of the substance present. o. Changes of Matter o Physical Changes: o Changes in matter that do not change the composition of a substance. o. o Chemical Changes: o Changes that result in new substances. o. Chemical Reactions o In the course of a chemical reaction, the reacting substances are. Compounds Compounds can be broken down into more elemental particles by only. Give It Some Thought: Which of the following is a physical change, and which is a chemical change? Circle One. a. Plants use carbon dioxide and water to make sugar: 1. a chemical change 2. cannot determine without additional information 3. neither a physical nor a chemical change 4. a physical change b. Water vapor in the air on a cold day forms frost. 1. a chemical change 2. cannot determine without additional information 3. neither a physical nor a chemical change 4. a physical change Separation of Mixtures o Involves only based on unique physical properties. Distillation: o Separates homogeneous mixture on the basis of differences in. Filtration: o Separates from liquids and solutions. Chromatography: o Separates substances on the basis of differences in in a solvent. 5
1.4 Units of Measurement SI Units Physical Quantity Name of Unit Abbreviation Mass Kilogram Length Meter Time Second Temperature Kelvin Amount of Substance Mole Electric Current Ampere Luminous intensity Candela Système International d Unités Uses a different base unit for each quantity Metric System o Prefixes convert the base units into units that are appropriate for the item being measured. Prefix Abbreviation Meaning Giga Mega Kilo Deci Centi Milli Micro Nano Pico Femto Give It Some Thought: Which of the following quantities is the smallest? (Circle One) 1. 1 mg 2. 1 µg 3. 1 pg A microgram is equal to how many grams? 1. 1 x 10 6 2. 1 x 10 3 3. 10 4. 1 x 10-3 5. 1 x 10-6 Volume o The most commonly used metric units for volume are the and the o A liter is a cube 1 dm long on each side. o A milliliter is a cube 1 cm long on each side. 6
Uncertainty in Measurements Different measuring devices have different uses and different degrees of. Which of the following is the smallest volume? 1. 400 microliters 2. 4 milliliters 3. 0.4 centiliters 4. 4 x 10-5 liters 5. 4 x 10 5 nanoliters Temperature: o A measure of the average of the particles in a sample. Temperature o In scientific measurements, the scales are most often used. o The Celsius scale is based on the properties of water. o 0 C is the freezing point of water. o 100 C is the boiling point of water. Temperature o is the SI unit of temperature. o It is based on the properties of gases. o There are no negative Kelvin temperatures. o Temperature o The Fahrenheit scale is not used in scientific measurements. o o A temperature of 68 o F is equal to what temperature in degrees Celsius? The boiling point of liquid nitrogen is 77 K. What is this temperature in degrees Celsius? Density: o Physical property of a substance o A perfect cube of an unknown substance 10.0 cm in each dimension weighs 1.59 kg. What is the unknown s density (in g/cm 3 ) o Which will have the larger volume: 25g of Cu (8.94 g/cm 3 ) or 25g of Pb (11.34 g/cm 3 )? 7
o If you have equal masses of the following metals, which will occupy the largest volume? Au, density = 19.3 g/cm 3 Pb, density = 11.3 g/cm 3 Ag, density = 10.5 g/cm 3 Cu, density = 8.92 g/cm 3 Al, density = 2.70 g/cm 3 1.5 Uncertainty in Measurement Accuracy versus Precision o refers to the proximity of a measurement to the true value of a quantity. o refers to the proximity of several measurements to each other. Give It Some Thought: Which of the following is an inexact quantity? 1. The number of people in your chemistry class 2. The mass of a penny 3. The number of grams in a kilogram Significant Figures o The term refers to digits that were measured. o When rounding calculated numbers, we pay attention to significant figures so we do not overstate the accuracy of our answers. Significant Figures 1. All nonzero digits are significant. 2. Zeroes between two significant figures are themselves significant. 3. Zeroes at the beginning of a number are never significant. 4. Zeroes at the end of a number are significant if a decimal point is written in the number. Significant Figures o When addition or subtraction is performed, answers are rounded to the least significant. o When multiplication or division is performed, answers are rounded to the number of digits that corresponds to the number of significant figures in any of the numbers used in the calculation. Give It Some Thought: How do we determine how many digits to use in conversion factors? 1. Conversion factors must have at least half as many significant figures as the data. 2. The number of significant figures in conversion factors does not matter. 3. Conversion factors must always have at least the number of significant figures as the data being converted. 4. Conversion factors must have at least two more significant figures than the data being converted. How many significant figures are there in the following number: 1.200 x 10-9? 8
How many significant figures are there in the following summation? 6.220 1.0 +125 How many significant figures are there in the result of the following multiplication? (2.54) x (6.2) x (12.000) How many significant figures should be shown for the calculation? 1.25 + 0.45 2.734 9