Tro CHEMISTRY; A Molecular Approach

Tro CHEMISTRY; A Molecular Approach
1.1 Atoms and Molecules 1.2 The Scientific Approach to Knowledge 1.3 The Classification of Matter 1.4 Physical and Chemical Changes and Physical and Chemical Properties 1.5 Energy: A Fundamental Part of Physical and Chemical Change 1.6 The Units of Measurement 1.7 The Reliability of a Measurement 1.8 Solving Chemical Problems Chapter 1 Matter, Measurement, and Problem Solving

Tro, Chemistry: A Molecular Approach - Chap 1
Chemistry in Our World Cosmetics Fuels Pollution Food/Additives Metals/Corrosion Chemistry affects our everyday life in ways that you probably never imagined. How many people drove to school this morning? Do you put gasoline in you car? Without the chemical reaction called combustion you would still be driving a horse and buggy. How many people walked up the sidewalk? Did you know that cement or concrete is formed from a chemical reaction of compounds formed from limestone, chalk, and clay, with water. Tro, Chemistry: A Molecular Approach - Chap 1

Question Question Over 25 million chemicals are known. Can you list some examples? Sources and uses? Over 25 million chemicals are known. Can you list some examples? Sources and uses? Write down the common student responses along with the student names. Alcohol, Salt (2006) Tro, Chemistry: A Molecular Approach - Chap 1

Types of Chemicals Natural Plant sources Animal Sources Mineral Sources Synthetic Medicines Plastics Fibers Where do chemicals come from? You may be surprised to find that chemicals can come from many places. They may come from plant sources; in fact in early times, a chemical precursor to aspirin came from extracts of willow trees. Many modern day chemicals are isolated from plants or animals. Some chemicals come from mineral sources. Rock salt is mined from huge underground reserves for use in the winter. Many other minerals are mined for use as is, or sometimes refined and chemically reacted to provide other chemicals for everyday use. How many girls in here are wearing lipstick? The Lipstick that you are wearing may contain Bismuth oxychloride, which is synthetic pearl, which helps to imparts a frost or shine to your lipstick. Bismuth is the by-product of lead and copper refining, as well as other metals to a smaller degree. Bismuth occurs very rarely in nature. It is on the periodic table of elements under the symbol Bi at atomic number 83. It is very heavy and chemically resembles arsenic and antimony. It has a whitish/iridescent hue and has a very high shine property to it. Of all the heavy metals it is the only non-toxic. Bimsuth is a carrier for fuel in nuclear reactors. Bismuth components are used in everything from detection work, to making acrylic fibers, to safety devices in fire detection and extinguishing items, soldering, magnets and medicine as well as cosmetics. Because it is a by-product of lead refining, bismuth oxychloride should be lead free when companies begin using it in their cosmetics. Source: Tro, Chemistry: A Molecular Approach - Chap 1

The branch of science that deals with the characteristics, properties, composition, and reactions of all materials. What do we mean by “reaction”? Iron reacts with oxygen to form rust: 4Fe(s) + 3O2(g) Fe2O3(s) solid/metal gas red solid Chemistry deals with the propertied of materials and the changes materials undergo. When a chemical change occurs we say that a reaction has taken place. The chemical or chemicals involved have somehow changed their chemical composition. Here is an example. The iron of this nail is rusting (or undergoing a chemical reaction) to form iron oxide Rust Tro, Chemistry: A Molecular Approach - Chap 1

Chemistry is Important Economically
25 million chemicals known. 5 million chemicals discovered each year. Chemical industry is fifth largest in the US. US sales over $550 billion. 1 million people are employed. In 2005, US produced 36,520,000 metric tons of Sulfuric Acid. I think that I may have impressed upon you the importance of chemistry, but here are some more facts that may interest you further. Chemical and Engineering News 2005. Tro, Chemistry: A Molecular Approach - Chap 1

Discuss …virtually every industry or business that makes or sells a product is involved with chemicals and, therefore with chemistry (Burns, 2003) Do you believe this statement? Can you think of any exceptions? Does this surprise you? Tro, Chemistry: A Molecular Approach - Chap 1

Structure Determines Properties
the properties of matter are determined by the atoms and molecules that compose it composed of one carbon atom and one oxygen atom colorless, odorless gas burns with a blue flame binds to hemoglobin carbon monoxide composed of one carbon atom and two oxygen atoms colorless, odorless gas incombustible does not bind to hemoglobin carbon dioxide Tro, Chemistry: A Molecular Approach - Chap 1

Atoms and Molecules atoms are submicroscopic particles are the fundamental building blocks of all matter molecules two or more atoms attached together attachments are called bonds attachments come in different strengths molecules come in different shapes and patterns Chemistry is the science that seeks to understand the behavior of matter by studying the behavior of atoms and molecules Tro, Chemistry: A Molecular Approach - Chap 1

The Scientific Approach to Knowledge
philosophers try to understand the universe by reasoning and thinking about “ideal” behavior scientists try to understand the universe through empirical knowledge gained through observation and experiment One of the goals of scientists is to solve problems. For chemists we want to solve chemical problems. There is a specific method that we use to approach problem solving. It is called the scientific method. It is a systematic approach to research. First you must carefully define the problem. Next you perform experiments, make observations, record information or DATA. Then you analyze the data, you form an idea (a hypothesis) that explains the data and observations. Then you repeat the process. You use a new plan or conduct new experiments to determine if your hypothesis is sound Over time, a hypothesis that becomes widely accepted is called a theory or a law. These are concise statements that explain the relationship between observed phenomena that are always the same under given conditions. Laws are usually given in terms of a mathematical definition. Tro, Chemistry: A Molecular Approach - Chap 1

From Observation to Understanding
Hypothesis – a tentative interpretation or explanation for an observation falsifiable – confirmed or refuted by other observations tested by experiments – validated or invalidated when similar observations are consistently made, it can lead to a Scientific Law a statement of a behavior that is always observed summarizes past observations and predicts future ones Law of Conservation of Mass This process of experimentation to describe nature is called the scientific method. It always follows the same form. An observation in made, you come up with an explanation, then you test to see if your explanation holds water. repeat the process. A hypothesis is a proposal about an observation. You have to provide experiments to test you hypothesis. A theory is a well-established hypothesis. It is well accepted. It usually is still under consideration and scientists are planning experiments to continue to test the theory. Tro, Chemistry: A Molecular Approach - Chap 1

From Specific to General Understanding
a hypothesis is a potential explanation for a single or small number of observations a theory is a general explanation for the manifestation and behavior of all nature models pinnacle of scientific knowledge validated or invalidated by experiment and observation This overhead helps to define some of these terms associated with the scientific method. An experiment is controlled research. The idea of controlling the variables in the experiment is very important. A law is a concise statement that summarize the behavior of nature and has no exceptions. These are hypotheses that have been around for a long time and have gained universal acceptance. Tro, Chemistry: A Molecular Approach - Chap 1

Scientific Method a test of a hypothesis or theory a tentative explanation of a single or small number of natural phenomena a general explanation of natural phenomena Another way to visualize the scientific method. Notice the flow from one step to another. Usually this process is repeated by many, many chemists before the process is ever called complete. And in truth the steps are never finished. An experiment conducted tomorrow may show that one of our trusted and beloved laws may have exceptions, and then the process would start all over again. the careful noting and recording of natural phenomena a generally observed natural phenomenon Tro, Chemistry: A Molecular Approach - Chap 1

Which Beaker is Empty? Which glass is empty! Right! Neither one is empty. Tro, Chemistry: A Molecular Approach - Chap 1

Classification of Matter
matter is anything that has mass and occupies space we can classify matter based on whether it’s solid, liquid, or gas Everything is made up of matter. By definition all matter has mass and takes up space. Chemistry is the branch of science that is concerned with matter. How it behaves and what reactions it undergoes. The Mass of an object measures how much matter is present. (Get a demo, use a mass from the physics lab, 1 kilogram would work nicely) Don’t get mass confused with weight. Weight is a measure of how strongly an object is attracted to the earth. A 1 kilogram object has a weight of 2.2 pounds on earth, but weighs much less on the moon. (Approximately 1/6th the weight.) Tro, Chemistry: A Molecular Approach - Chap 1

Classifying Matter by Physical State
matter can be classified as solid, liquid, or gas based on the characteristics it exhibits This table summarizes some of the properties of solids liquids and gasses. DEMO, use the gas demo to show the compression of a gas. The three common physical states have some other properties that you should know. Solids cannot be compressed. This is because the particles that make up the solid are in a rigid structure where the particles are touching. There is no room to compress a solid. Liquids have very little compressibility. The particles in a liquid are touching, but they are not in a rigid structure. There may be some small amount of room to squeeze the particles together, but NOT very much. Gasses can be compressed a lot. The particles of a gas are not touching. In fact most of the space is empty. Therefore you can easily compress a gas. Fixed = keeps shape when placed in a container Indefinite = takes the shape of the container Tro, Chemistry: A Molecular Approach - Chap 1

Solids the particles in a solid are packed close together and are fixed in position though they may vibrate the close packing of the particles results in solids being incompressible the inability of the particles to move around results in solids retaining their shape and volume when placed in a new container, and prevents the particles from flowing Tro, Chemistry: A Molecular Approach - Chap 1

Crystalline Solids some solids have their particles arranged in an orderly geometric pattern – we call these crystalline solids salt and diamonds Tro, Chemistry: A Molecular Approach - Chap 1

Amorphous Solids some solids have their particles randomly distributed without any long-range pattern – we call these amorphous solids plastic glass charcoal Tro, Chemistry: A Molecular Approach - Chap 1

Liquids the particles in a liquid are closely packed, but they have some ability to move around the close packing results in liquids being incompressible but the ability of the particles to move allows liquids to take the shape of their container and to flow – however, they don’t have enough freedom to escape and expand to fill the container Tro, Chemistry: A Molecular Approach - Chap 1

Gases in the gas state, the particles have complete freedom from each other the particles are constantly flying around, bumping into each other and the container in the gas state, there is a lot of empty space between the particles Tro, Chemistry: A Molecular Approach - Chap 1

Gases particles can be squeezed closer together – therefore gases are compressible particles are not held in close contact and are moving freely, gases expand to fill and take the shape of their container, and will flow Tro, Chemistry: A Molecular Approach - Chap 1

Classification of Matter by Composition
matter whose composition does not change from one sample to another is called a pure substance made of a single type of atom or molecule composition is the same, samples have the same characteristics matter whose composition may vary from one sample to another is called a mixture two or more types of atoms or molecules combined in variable proportions because composition varies, samples have different characteristics What is the difference between mixtures and pure substance? This room contains a mixture of men and women. There is more than one distinct entity. This side of the room, or this table contains only men. This is only one type of entity. Elements and compounds are both examples of pure substances, but… What is the difference between an element and a compound? An element is a fundamental substance. It has properties that define it, and it cannot be broken down into simpler substances. Compounds are made of two or more elements in FIXED proportion. Tro, Chemistry: A Molecular Approach - Chap 1

Classification of Matter by Composition
made of one type of particle all samples show the same intensive properties made of multiple types of particles samples may show different intensive properties Tro, Chemistry: A Molecular Approach - Chap 1

Classification of Pure Substances
substances that cannot be broken down into simpler substances by chemical reactions are called elements basic building blocks of matter composed of single type of atom All elements are defined by the properties of the single type of atom that makes up that pure substance. What is an atom. It is the smallest elemental particle that retains the properties of the element. All of the particles of a sample of an element (for example, copper) have something in common. Atoms cannot be subdivided without destroying them. The periodic table is a list of all known elements. Tro, Chemistry: A Molecular Approach - Chap 1

Periodic Table of the Elements
Insert periodic table here We will spend a great deal of time discussing the elements in another chapter. As of 2005, there are 116 known elements: 93 occur naturally on earth (including technetium and plutonium), and 94 (including promethium) have been detected in the universe at large. 11 exist under standard conditions as gasses. 2 exist as liquids, the remainder exist as solids. The 23 elements not found on earth are derived artificially; technetium was the first purportedly non-naturally occurring element to be synthesized, in 1937, although trace amounts of technetium have since been found in nature. All artificially derived elements are radioactive with short half-lives, so if any atoms of these elements were present at the formation of Earth are extremely likely to have already decayed. Tro, Chemistry: A Molecular Approach - Chap 1

Classification of Pure Substances: Cont.
substances that can be decomposed are called compounds chemical combinations of elements composed of molecules that contain two or more different kinds of atoms all molecules of a compound are identical, so all samples of a compound behave the same way most natural pure substances are compounds A compound is a pure substance that is made up of elements in definite proportion. There is a formula, or recipe that describes which elements and how many of each. compounds have VERY different chemical and physical properties than the elements from which they were made. Water, a liquid at RT is made from two gasses, hydrogen and oxygen. Salt, sodium chloride, a relatively unreactive solid is made from sodium which is a very reactive metal and chlorine which is a reactive and poisonous gas. Tro, Chemistry: A Molecular Approach - Chap 1

Classification of Pure Substances
made of one type of atom (some elements found as multi-atom molecules in nature) combine together to make compounds made of one type of molecule, or array of ions molecules contain 2 or more different kinds of atoms Tro, Chemistry: A Molecular Approach - Chap 1

Classification of Mixtures
homogeneous = mixture that has uniform composition throughout every piece of a sample has identical characteristics, though another sample with the same components may have different characteristics atoms or molecules mixed uniformly heterogeneous = mixture that does not have uniform composition throughout contains regions within the sample with different characteristics atoms or molecules not mixed uniformly If elements and compounds are examples of pure substances, What are mixtures? Mixtures are combinations of pure substances where the composition is not fixed. There are many different names for mixtures. When we dissolve sugar in water we call the resulting mixture a solution. There are even different types of mixtures… Homogeneous. Meaning uniform. Heterogeneous. Not uniform. Tro, Chemistry: A Molecular Approach - Chap 1

Classification of Mixtures
made of multiple substances, whose presence can be seen portions of a sample have different composition and properties made of multiple substances, but appears to be one substance all portions of a sample have the same composition and properties Tro, Chemistry: A Molecular Approach - Chap 1

Classification of Matter
Insert figure 2.9 This flow chart shows the organization of matter into pure substances and mixtures. Tro, Chemistry: A Molecular Approach - Chap 1

Separation of Mixtures
separate mixtures based on different physical properties of the components Physical change Centrifugation & Decanting Density Evaporation Volatility Chromatography Adherence to a Surface Filtration State of Matter (solid/liquid/gas) Distillation Boiling Point Technique Different Physical Property Tro, Chemistry: A Molecular Approach - Chap 1

Distillation Tro, Chemistry: A Molecular Approach - Chap 1

Filtration Tro, Chemistry: A Molecular Approach - Chap 1

Changes in Matter changes that alter the state or appearance of the matter without altering the composition are called physical changes changes that alter the composition of the matter are called chemical changes during the chemical change, the atoms that are present rearrange into new molecules, but all of the original atoms are still present Matter can undergo changes. Physical changes describe a change in the substance that does not alter the composition of the substance. If we melt an ice cube, the substance itself does not change. Before melting we had a cube of solid water. After we melt the ice cube we have a puddle of liquid water. The substance is still water. Boiling is another example of a physical change. Cutting a substance into smaller pieces does not alter the substance. If we take a piece of lumber and cut it into smaller pieces, the substance is still wood. Even the sawdust is still wood pieces. The substance has not changed. Chemical changes are a change in matter the alters the composition of the substance. After a chemical change we have a new substance with new properties. Or we may even have a mixture of two or more new substances with their own properties. Tro, Chemistry: A Molecular Approach - Chap 1

Physical Changes in Matter
The boiling of water is a physical change. The water molecules are separated from each other, but their structure and composition do not change. Tro, Chemistry: A Molecular Approach - Chap 1

Common Physical Changes
Dissolving of Sugar C12H22O11(s) C12H22O11(aq) processes that cause changes in the matter that do not change its composition state changes boiling / condensing melting / freezing subliming CO2(s) CO2(g) Dry Ice Subliming of Dry Ice dissolving Tro, Chemistry: A Molecular Approach - Chap 1

Chemical Changes in Matter
The rusting of iron is a chemical change. The iron atoms in the nail combine with oxygen atoms from O2 in the air to make a new substance, rust, with a different composition. Tro, Chemistry: A Molecular Approach - Chap 1

Common Chemical Changes
C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(l) processes that cause changes in the matter that change its composition rusting processes that release lots of energy burning Tro, Chemistry: A Molecular Approach - Chap 1

Properties of Matter physical properties are the characteristics of matter that can be changed without changing its composition characteristics that are directly observable chemical properties are the characteristics that determine how the composition of matter changes as a result of contact with other matter or the influence of energy characteristics that describe the behavior of matter All substances have properties that we can observe. These properties are what identify the substance and distinguish it from other substances. There are two classes of properties. Physical properties and chemical properties. Tro, Chemistry: A Molecular Approach - Chap 1

Energy Changes in Matter
changes in matter, both physical and chemical, result in the matter either gaining or releasing energy energy is the capacity to do work work is the action of a force applied across a distance a force is a push or a pull on an object electrostatic force is the push or pull on objects that have an electrical charge Energy is a measure of an object or systems potential to do work. Work is the application of a force over a distance. Try to remember these definitions as we discuss matter in this chapter. Tro, Chemistry: A Molecular Approach - Chap 1

Energy of Matter all matter possesses energy energy is classified as either kinetic or potential energy can be converted from one form to another when matter undergoes a chemical or physical change, the amount of energy in the matter changes as well There are many different types of energy. Kinetic energy is the energy that matter has due to its motion or velocity. KE = ½mv2 Potential energy is energy stored in the matter due to several factors. You can have gravitational potential energy. Electrical potential energy Magnetic potential energy Chemical potential energy Tro, Chemistry: A Molecular Approach - Chap 1

Energy of Matter - Kinetic
kinetic energy is energy of motion motion of the atoms, molecules, and subatomic particles thermal (heat) energy is a form of kinetic energy because it is caused by molecular motion Tro, Chemistry: A Molecular Approach - Chap 1

Energy of Matter - Potential
potential energy is energy that is stored in the matter due to the composition of the matter and its position in the universe chemical potential energy arises from electrostatic forces between atoms, molecules, and subatomic particles Tro, Chemistry: A Molecular Approach - Chap 1

Conversion of Energy you can interconvert kinetic energy and potential energy whatever process you do that converts energy from one type or form to another, the total amount of energy remains the same Law of Conservation of Energy The first law of thermodynamics is the law of conservation of energy. The law of conservation of energy States that energy cannot be created or destroyed in a chemical reaction, it is only converted between forms or moved from one location to another. Tro, Chemistry: A Molecular Approach - Chap 1

Spontaneous Processes
materials that possess high potential energy are less stable processes in nature tend to occur on their own when the result is material(s) with lower total potential energy processes that result in materials with higher total potential energy can occur, but generally will not happen without input of energy from an outside source when a process results in materials with less potential energy at the end than there was at the beginning, the difference in energy is released into the environment Tro, Chemistry: A Molecular Approach - Chap 1

Potential to Kinetic Energy
Tro, Chemistry: A Molecular Approach - Chap 1

Question What do scientists measure? According to ‘google’ what do they measure? scientists measure - Google Search What do scientists measure? Right! Things like how many licks it takes to get to the center of a tootsie-pop According to the preeminent source of information in the world… google… scientists measure… Well they measure a lot of stuff. Tro, Chemistry: A Molecular Approach - Chap 1

The Standard Units Scientists have agreed on a set of international standard units for comparing all our measurements called the SI units Système International = International System Quantity Unit Symbol length meter m mass kilogram kg time second s temperature kelvin K Lets take a look at the base units. These are the seven fundamental units in the SI system. Read and explain the units. Tro, Chemistry: A Molecular Approach - Chap 1

Length Measure of the two-dimensional distance an object covers often need to measure lengths that are very long (distances between stars) or very short (distances between atoms) SI unit = meter About 3.37 inches longer than a yard 1 meter = one ten-millionth the distance from the North Pole to the Equator = distance between marks on standard metal rod = distance traveled by light in a specific period of time Commonly use centimeters (cm) 1 m = 100 cm 1 cm = 0.01 m = 10 mm 1 inch = 2.54 cm (exactly) The SI unit of length is the meter (m) 1 foot = meters 1 ft = m It is important that you have an understanding of the relative size of the common units of length. Tro, Chemistry: A Molecular Approach - Chap 1

Mass Measure of the amount of matter present in an object weight measures the gravitational pull on an object, which depends on its mass SI unit = kilogram (kg) about 2 lbs. 3 oz. Commonly measure mass in grams (g) or milligrams (mg) 1 kg = pounds, 1 lbs. = g 1 kg = 1000 g = 103 g 1 g = 1000 mg = 103 mg 1 g = kg = 10-3 kg 1 mg = g = 10-3 g Tro, Chemistry: A Molecular Approach - Chap 1

Mass Equivalents Insert figure 3.10 Tro, Chemistry: A Molecular Approach - Chap 1

Time measure of the duration of an event SI units = second (s) 1 s is defined as the period of time it takes for a specific number of radiation events of a specific transition from cesium-133 Tro, Chemistry: A Molecular Approach - Chap 1

Temperature measure of the average amount of kinetic energy higher temperature = larger average kinetic energy heat flows from the matter that has high thermal energy into matter that has low thermal energy until they reach the same temperature heat is exchanged through molecular collisions between the two materials Tro, Chemistry: A Molecular Approach - Chap 1

Temperature Scales Fahrenheit Scale, °F used in the U.S. Celsius Scale, °C used in all other countries Kelvin Scale, K absolute scale no negative numbers directly proportional to average amount of kinetic energy 0 K = absolute zero Notice in this graphic that since the Kelvin scale is based on the Celsius scale the amount of temperature change per division on the scale is the same, but the label, or number that corresponds to that temperature is different. Tro, Chemistry: A Molecular Approach - Chap 1

A Comparison of Temperature Scales
Here is another comparison of the temperature scales which show a few more temperatures for comparison. Tro, Chemistry: A Molecular Approach - Chap 1

Again, another graphic that shows the relationship between the freezing point of water and the different temperature scales used. Tro, Chemistry: A Molecular Approach - Chap 1

Kelvin vs. Celsius the size of a “degree” on the Kelvin scale is the same as on the Celsius scale though technically, we don’t call the divisions on the Kelvin scale degrees; we called them kelvins! so 1 kelvin is 1.8 times larger than 1°F the 0 standard on the Kelvin scale is a much lower temperature than on the Celsius scale Because the temperature scales have different zero points, formulas must be used to carry out the conversions. In order to convert between Celsius and Kelvin you must add to the Celsius reading. To convert from Kelvin to Celsius, you reverse the process and subtract from the Kelvin reading. Tro, Chemistry: A Molecular Approach - Chap 1

Fahrenheit vs. Celsius a Celsius degree is 1.8 times larger than a Fahrenheit degree the standard used for 0° on the Fahrenheit scale is a lower temperature than the standard used for 0° on the Celsius scale Since the graduations on the Fahrenheit scale and Celsius scale the conversion is more difficult. Tro, Chemistry: A Molecular Approach - Chap 1

Example 1.2 Convert 40.00 °C into K and °F
Find the equation that relates the given quantity to the quantity you want to find Given: Find: Equation: 40.00 °C K K = °C Since the equation is solved for the quantity you want to find, substitute and compute K = °C K = K = K Find the equation that relates the given quantity to the quantity you want to find Given: Find: Equation: 40.00 °C °F Solve the equation for the quantity you want to find Substitute and compute

Related Units in the SI System
All units in the SI system are related to the standard unit by a power of 10 The power of 10 is indicated by a prefix multiplier The prefix multipliers are always the same, regardless of the standard unit Report measurements with a unit that is close to the size of the quantity being measured In order to be able to communicate with other scientists, we must have a logical and universal system for comparing measurements. The most common system is called the Metric system. Also known as the International system or Systeme International (SI system for short) It is a system arranged on powers of 10. For every fundamental measurement there is a base unit. In order to describe measurements that are smaller or larger than the base, we use powers of 10. Tro, Chemistry: A Molecular Approach - Chap 1

Prefixes Used with SI Units
There are prefixes to the SI units; often the regular units are too small or too large for our use. Common prefixes SI Base Units giga 109 Mega 106 Kilo 103 Centi 10-2 Milli 10-3 Micro 10-6 Nano 10-9 These prefixes allow us to use units like Centimeter Kilogram Milliliter Notice that each prefix has an exponential power or notation. 1 kilogram means the same as 1x103 grams 1 microgram means the same as 1x10-6 grams Tro, Chemistry: A Molecular Approach - Chap 1

Volume Derived unit any length unit cubed Measure of the amount of space occupied SI unit = cubic meter (m3) Commonly measure solid volume in cubic centimeters (cm3) 1 m3 = 106 cm3 1 cm3 = 10-6 m3 = m3 Commonly measure liquid or gas volume in milliliters (mL) 1 L is slightly larger than 1 quart 1 L = 1 dm3 = 1000 mL = 103 mL 1 mL = L = 10-3 L 1 mL = 1 cm3 Tro, Chemistry: A Molecular Approach - Chap 1

Metric Volume and Length Relationships
Insert figure 3.5 Here is that relationship pictorally. Tro, Chemistry: A Molecular Approach - Chap 1

Common Units and Their Equivalents
Length 1 kilometer (km) = mile (mi) 1 meter (m) 39.37 inches (in.) 1.094 yards (yd) 1 foot (ft) 30.48 centimeters (cm) 1 inch (in.) 2.54 centimeters (cm) exactly Tro, Chemistry: A Molecular Approach - Chap 1

Common Units and Their Equivalents
Mass 1 kilogram (km) = 2.205 pounds (lb) 1 pound (lb) grams (g) 1 ounce (oz) 28.35 grams (g) Volume 1 liter (L) = 1000 milliliters (mL) 1000 cubic centimeters (cm3) 1.057 quarts (qt) 1 U.S. gallon (gal) 3.785 liters (L) Tro, Chemistry: A Molecular Approach - Chap 1

Intensive Properties Do not depend on the amount of substance. Melting point Boiling point Color Flammability Reactivity Conductivity Physical State (solid, liquid, gas) The properties of substances can be classified by two other terms. Intensive and extensive. Intensive properties DO NOT depend on the amount of material. For example, melting point or boiling point. It does not matter if you have 1 gram of water or one ton of water. Water melts at 0oC and boils at 100oC. Color is another intensive property. Flammability, reactivity, conductivity, Intensive properties can be a physical property or a chemical property. Intensive Properties can be Chemical or Physical Tro, Chemistry: A Molecular Approach - Chap 1

Extensive Properties Depend on the amount of material present Mass Volume Length Moles Weight Total amount of heat given off in combustion Extensive properties are properties that depend upon the amount of the substance present. For example, Mass. This is logical. The greater the amount of a substance present, the greater the sample’s mass. Volume, length, moles, weight. All examples of extensive properties. Many measurements can depend upon the amount of substance present. The total heat given off in a combustion reaction. For example, on a cool autumn evening, would you like to be gathered around a nice campfire, a lit match, or in the middle of a raging forest fire? Again extensive properties can be a chemical property or a physical property. Extensive Properties can be Chemical or Physical Tro, Chemistry: A Molecular Approach - Chap 1

Mass & Volume two main physical properties of matter mass and volume are extensive properties the value depends on the quantity of matter extensive properties cannot be used to identify what type of matter something is if you are given a large glass containing 100 g of a clear, colorless liquid and a small glass containing 25 g of a clear, colorless liquid - are both liquids the same stuff? even though mass and volume are individual properties, for a given type of matter they are related to each other! Tro, Chemistry: A Molecular Approach - Chap 1

Mass vs. Volume of Brass Tro, Chemistry: A Molecular Approach - Chap 1

Volume vs. Mass of Brass y = 8.38x 20 40 60 80 100 120 140 160 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 Volume, cm3 Mass, g Tro, Chemistry: A Molecular Approach - Chap 1

Density Ratio of mass:volume is an intensive property value independent of the quantity of matter Solids = g/cm3 1 cm3 = 1 mL Liquids = g/mL Gases = g/L Volume of a solid can be determined by water displacement – Archimedes Principle Density : solids > liquids >>> gases except ice is less dense than liquid water! Density is a very important property of matter. It is a derived unit and is defined as the mass of an object divided by its volume. Density is a measure of how compact or tightly packed an object is. In SI units, density is kg/m3, but often we use more convenient units of grams/ml. Specific gravity is a comparison of the density of an object to the density of water. Since the density of water is 1.00 g/ml, the specific gravity of a substance is a unitless number. Tro, Chemistry: A Molecular Approach - Chap 1

Density For equal volumes, denser object has larger mass For equal masses, denser object has smaller volume Heating an object generally causes it to expand, therefore the density changes with temperature Tro, Chemistry: A Molecular Approach - Chap 1

Example 1. 3 Decide if a ring with a mass of 3. 15 g that displaces 0
Example 1.3 Decide if a ring with a mass of 3.15 g that displaces cm3 of water is platinum Find the equation that relates the given quantity to the quantity you want to find Given: Find: Equation: mass = 3.15 g volume = cm3 density, g/cm3 Since the equation is solved for the quantity you want to find, and the units are correct, substitute and compute Compare to accepted value of the intensive property Density of platinum = 21.4 g/cm3 therefore not platinum

Measurement Components of Measurement Numerical quantity Unit Name of substance For example, 325.0 mL water Every measurement has some essential components. First there has to be a number, the measurement, I have 7. 7 what. Second there has to be a unit. 7 cans. 7 pairs. 7 pounds. Finally there has to be a description of the thing that was measured. A name. Numerical quantity unit Name of substance Tro, Chemistry: A Molecular Approach - Chap 1

Components of Measurement
Components of a Measurement Numerical Quantity, Unit, Name of substance All three of these components of the measurement are very important. Every measurement has some essential components, First there has to be a number. The measurement: “I have 7” But a number itself is not a measurement… “7 what” “7 pounds, 7 feet, 7 amps…” There has to be a unit. Finally we need a name or a discriptor of the thing being measured. “I have 7 pounds of pennies, 7 pounds of jelly beans, 7 pounds of gourmet coffee” Without any one of these three things, a measurement is meaningless. Just ask NASA! Do you remember the $125 Mars orbiter that crashed into the Mars surface in The failure was due to the two teams working on the lander not conveying all the information about a length measurement to one another. NASA's metric confusion caused Mars orbiter loss NASA's Climate Orbiter was lost September 23, 1999 September 30, 1999 Web posted at: 1:46 p.m. EDT (1746 GMT) (CNN) -- NASA lost a $125 million Mars orbiter because one engineering team used metric units while another used English units for a key spacecraft operation, according to a review finding released Thursday. For that reason, information failed to transfer between the Mars Climate Orbiter spacecraft team at Lockheed Martin in Colorado and the mission navigation team in California. Lockheed Martin built the spacecraft. Tro, Chemistry: A Molecular Approach - Chap 1

What Is a Measurement? quantitative observation comparison to an agreed- upon standard every measurement has a number and a unit Tro, Chemistry: A Molecular Approach - Chap 1

A Measurement the unit tells you what standard you are comparing your object to the number tells you what multiple of the standard the object measures the uncertainty in the measurement scientific measurements are reported so that every digit written is certain, except the last one which is estimated Tro, Chemistry: A Molecular Approach - Chap 1

Estimating the Last Digit
for instruments marked with a scale, you get the last digit by estimating between the marks if possible mentally divide the space into 10 equal spaces, then estimate how many spaces over the indicator mark is Tro, Chemistry: A Molecular Approach - Chap 1

Reading a Volumetric Device
Insert figure 3.13 Note the Meniscus When you read a buret, a graduated cylinder, or a graduated pipet, you must try to read the meniscus of the liquid inside the device. most of the time, the meniscus does not match exactly with one of the graduations on the device. You must therefore estimate the position of the meniscus. In this example the level of the meniscus is between the 6.2 ml mark and the 6.3 ml mark. One person may look at the level of the liquid and estimate that the meniscus is at Another may estimate that it is at 6.22. The last digit in your reading is not certain. You are certain that it is more than 6.2 ml, but you are not 100% certain how much more. Tro, Chemistry: A Molecular Approach - Chap 1

The # of S.F. Depends Upon the Device
Figure 1.14 The precision of the device is dependant upon how the device was constructed. Here is an example of two different thermometers. The one on the left was made with very fine graduations. The gradutations represent a tenth of a degree. The one on the right was made with graduations that represent single degrees. When both thermometers are reading the temperature of the same object, a person reading the scales is able to read the one on the left with more precision. Tro, Chemistry: A Molecular Approach - Chap 1

Significant Figures the non-place-holding digits in a reported measurement are called significant figures some zeros in a written number are only there to help you locate the decimal point significant figures tell us the range of values to expect for repeated measurements the more significant figures there are in a measurement, the smaller the range of values is 12.3 cm has 3 sig. figs. and its range is 12.2 to 12.4 cm 12.30 cm has 4 sig. figs. and its range is 12.29 to cm When we make measurements, we MUST report our data in a method so that others know by looking at the data how much certainty we have that our measurement represents the true value for the quantity we were measuring. The Significant figures in a measurement are those digits in a measured number including all certain digits plus a final one, which is semi-uncertain. It is easiest to see how significant figures Tro, Chemistry: A Molecular Approach - Chap 1

Counting Significant Figures
All non-zero digits are significant 1.5 has 2 sig. figs. Interior zeros are significant 1.05 has 3 sig. figs. Leading zeros are NOT significant has 4 sig. figs. 1.050 x 10-3 These are the rules for finding the number of significant figures in a measurement. 1. nonzero digits are always significant 2. captive zeros must be significant, these are zeros that are stuck in between two non-zero digits. 3. leading zeros are not significant, these zeros are only there to hold place. Tro, Chemistry: A Molecular Approach - Chap 1

Counting Significant Figures
Trailing zeros may or may not be significant Trailing zeros after a decimal point are significant 1.050 has 4 sig. figs. Zeros at the end of a number without a written decimal point are ambiguous and should be avoided by using scientific notation if 150 has 2 sig. figs. then 1.5 x 102 but if 150 has 3 sig. figs. then 1.50 x 102 4. trailing zeros are significant if there is a decimal point. 5. The rule that causes all the problems is this last rule, zeros at end, no decimal point ??? Tro, Chemistry: A Molecular Approach - Chap 1

Significant Figures and Exact Numbers
Exact numbers have an unlimited number of significant figures A number whose value is known with complete certainty is exact from counting individual objects from definitions 1 cm is exactly equal to 0.01 m from integer values in equations in the equation for the radius of a circle, the 2 is exact Exact number is a number that arises from either counting items or defining a unit or a formula with an integer value. There are No uncertainties at all in exact numbers (hence their name). Do not apply to the significant figures rule. radius of a circle = diameter of a circle 2 Tro, Chemistry: A Molecular Approach - Chap 1

Example 1.5 Determining the Number of Significant Figures in a Number
How many significant figures are in each of the following? m km 10 dm = 1 m 1.000 × 105 s mm 10,000 m 4 sig. figs.; the digits 4 and 5, and the trailing 0 5 sig. figs.; the digits 5 and 3, and the interior 0’s infinite number of sig. figs., exact numbers 4 sig. figs.; the digit 1, and the trailing 0’s 1 sig. figs.; the digit 2, not the leading 0’s Ambiguous, generally assume 1 sig. fig. Tro, Chemistry: A Molecular Approach - Chap 1

Multiplication and Division with Significant Figures
when multiplying or dividing measurements with significant figures, the result has the same number of significant figures as the measurement with the fewest number of significant figures × , × = = 45 3 sig. figs sig. figs sig. figs. 2 sig. figs. ÷ 6.10 = = 4 sig. figs sig. figs sig. figs. There are also rules for determining the number of significant figures in an answer when you conduct multiplication or division. Multiplication and division: give the answer in significant figures as the measurement with the least amount of significant figures. Tro, Chemistry: A Molecular Approach - Chap 1

Addition and Subtraction with Significant Figures
when adding or subtracting measurements with significant figures, the result has the same number of decimal places as the measurement with the fewest number of decimal places = = 9.21 2 dec. pl dec. pl dec. pl. 2 dec. pl. = = 1 dec. pl dec. pl dec. pl. There are rules for determining the number of significant figures in an answer when you conduct addition or subtraction. Addition and subtraction: give the answer in as many decimal places as that of the smallest number Tro, Chemistry: A Molecular Approach - Chap 1

Rounding when rounding to the correct number of significant figures, if the number after the place of the last significant figure is 0 to 4, round down drop all digits after the last sig. fig. and leave the last sig. fig. alone add insignificant zeros to keep the value if necessary 5 to 9, round up drop all digits after the last sig. fig. and increase the last sig. fig. by one to avoid accumulating extra error from rounding, round only at the end, keeping track of the last sig. fig. for intermediate calculations When you conduct some mathematical manipulation as we have seen in the previous examples, you need to round your answer so that you have the correct number of significant figures. Tro, Chemistry: A Molecular Approach - Chap 1

Rounding rounding to 2 significant figures 2.34 rounds to 2.3 because the 3 is where the last sig. fig. will be and the number after it is 4 or less 2.37 rounds to 2.4 because the 3 is where the last sig. fig. will be and the number after it is 5 or greater rounds to 2.3 Tro, Chemistry: A Molecular Approach - Chap 1

Rounding rounding to 2 significant figures rounds to or 2.3 × 10-2 because the 3 is where the last sig. fig. will be and the number after it is 4 or less rounds to or 2.4 × 10-2 because the 3 is where the last sig. fig. will be and the number after it is 5 or greater rounds to or 2.3 × 10-2 Tro, Chemistry: A Molecular Approach - Chap 1

Rounding rounding to 2 significant figures 234 rounds to 230 or 2.3 × 102 because the 3 is where the last sig. fig. will be and the number after it is 4 or less 237 rounds to 240 or 2.4 × 102 because the 3 is where the last sig. fig. will be and the number after it is 5 or greater rounds to 230 or 2.3 × 102 Tro, Chemistry: A Molecular Approach - Chap 1

Both Multiplication/Division and Addition/Subtraction with Significant Figures when doing different kinds of operations with measurements with significant figures, do whatever is in parentheses first, evaluate the significant figures in the intermediate answer, then do the remaining steps × ( – ) = 2 dp dp × = 12 4 sf dp & 2 sf 2 sf Tro, Chemistry: A Molecular Approach - Chap 1

Example 1.6 Perform the following calculations to the correct number of significant figures b) Tro, Chemistry: A Molecular Approach - Chap 1

How many SF’s should be in the following answer?
19.3 – 18.4 1.07 = Some people recommend carrying all decimal places and working out S.F. at the end with multi-step calculations. Not always a good idea Although it is common practice in a multi-step problem to work out the answer on your calculator and then round the answer to some number of significant figures, this is not always a good idea. How many SF’s should be in the following answer? = s.f. (show intermediate step) Tro, Chemistry: A Molecular Approach - Chap 1

Uncertainty in Measured Numbers
uncertainty comes from limitations of the instruments used for comparison, the experimental design, the experimenter, and nature’s random behavior to understand how reliable a measurement is we need to understand the limitations of the measurement accuracy is an indication of how close a measurement comes to the actual value of the quantity precision is an indication of how reproducible a measurement is In the process of making any comparative measurement, there is some amount of uncertainty that comes from a combination the tool and the user. Precision- closeness of a set of values obtained from identical measurements Degree that measurements agree with one another Accuracy- closeness of a single measurement to its true value Tro, Chemistry: A Molecular Approach - Chap 1

Uncertainty in Measurement
Systematic Error (SE) - Values that are either all higher or all lower than the actual value Random Error (RE) - In the absence of SE, some values that are higher and some that are lower than the actual value Uncertainty in our measurements comes from two different sources… Systematic error or random error. Random errors are statistical fluctuations (in either direction) in the measured data due to the precision limitations of the measurement device. Random errors usually result from the experimenter's inability to take the same measurement in exactly the same way to get exact the same number. Systematic errors, by contrast, are reproducible inaccuracies that yields results that are all too high or too low. Systematic errors are often due to a problem which persists throughout the entire experiment. Tro, Chemistry: A Molecular Approach - Chap 1

Precision imprecision in measurements is caused by random errors errors that result from random fluctuations no specific cause, therefore cannot be corrected we determine the precision of a set of measurements by evaluating how far they are from the actual value and each other even though every measurement has some random error, with enough measurements these errors should average out Tro, Chemistry: A Molecular Approach - Chap 1

Accuracy inaccuracy in measurement caused by systematic errors errors caused by limitations in the instruments or techniques or experimental design can be reduced by using more accurate instruments, or better technique or experimental design we determine the accuracy of a measurement by evaluating how far it is from the actual value systematic errors do not average out with repeated measurements because they consistently cause the measurement to be either too high or too low Tro, Chemistry: A Molecular Approach - Chap 1

A Comparison of Accuracy and Precision
When making measurement, it is important to eliminate (as much a possible) any sources of uncertainty. This is part of the systematic process that we use called the scientific method. We are interested in investigating something and controlling the variables. This graphic shows the differences between accuracy and precision. It is possible to be very precise, but not accurate. This is probably the result of systematic error. A balance was not calibrated correctly. You measuring device has some problem. Tro, Chemistry: A Molecular Approach - Chap 1

Accuracy vs. Precision Tro, Chemistry: A Molecular Approach - Chap 1

Random or Systematic? random error Take a look at these graphs. Can you identify which one has random error in the data and which one has a systematic error? systematic error Tro, Chemistry: A Molecular Approach - Chap 1

Precise and Accurate? precise and accurate Which ones of these graphs shows data that is precise? Which ones of these graphs shows data that is accurate? precise but not accurate Tro, Chemistry: A Molecular Approach - Chap 1

Units Always write every number with its associated unit Always include units in your calculations you can do the same kind of operations on units as you can with numbers cm × cm = cm2 cm + cm = cm cm ÷ cm = 1 using units as a guide to problem solving is called dimensional analysis Tro, Chemistry: A Molecular Approach - Chap 1

Problem Solving and Dimensional Analysis
Many problems in chemistry involve using relationships to convert one unit of measurement to another Conversion factors are relationships between two units May be exact or measured Conversion factors generated from equivalence statements e.g., 1 inch = 2.54 cm can give or Tro, Chemistry: A Molecular Approach - Chap 1

Problem Solving and Dimensional Analysis
Arrange conversion factors so given unit cancels Arrange conversion factor so given unit is on the bottom of the conversion factor May string conversion factors So we do not need to know every relationship, as long as we can find something else the given and desired units are related to Tro, Chemistry: A Molecular Approach - Chap 1

Conceptual Plan a conceptual plan is a visual outline that shows the strategic route required to solve a problem for unit conversion, the conceptual plan focuses on units and how to convert one to another for problems that require equations, the conceptual plan focuses on solving the equation to find an unknown value Tro, Chemistry: A Molecular Approach - Chap 1

Concept Plans and Conversion Factors
Convert inches into centimeters Find relationship equivalence: 1 in = 2.54 cm Write concept plan in cm Change equivalence into conversion factors with starting units on the bottom Tro, Chemistry: A Molecular Approach - Chap 1

Systematic Approach Sort the information from the problem identify the given quantity and unit, the quantity and unit you want to find, any relationships implied in the problem Design a strategy to solve the problem Concept plan sometimes may want to work backwards each step involves a conversion factor or equation Apply the steps in the concept plan check that units cancel properly multiply terms across the top and divide by each bottom term Check the answer double check the set-up to ensure the unit at the end is the one you wished to find check to see that the size of the number is reasonable since centimeters are smaller than inches, converting inches to centimeters should result in a larger number Tro, Chemistry: A Molecular Approach - Chap 1

Example 1.7 Convert 1.76 yd. to centimeters
Sort information Given: Find: 1.76 yd length, cm Strategize Concept Plan: Relationships: 1 yd = m 1 m = 100 cm yd m cm Follow the concept plan to solve the problem Solution: Sig. figs. and round Round: cm = 161 cm Check Check: Units & magnitude are correct

Practice – Convert 30.0 mL to quarts (1 L = 1.057 qt)

Units & magnitude are correct
Convert 30.0 mL to quarts Sort information Given: Find: 30.0 mL volume, qts Strategize Concept Plan: Relationships: 1 L = qt 1 L = 1000 mL mL L qt Follow the concept plan to solve the problem Solution: Sig. figs. and round Round: qt = qt Check Check: Units & magnitude are correct

Concept Plans for Units Raised to Powers
Convert cubic inches into cubic centimeters Find relationship equivalence: 1 in = 2.54 cm Write concept plan in3 cm3 Change equivalence into conversion factors with given unit on the bottom Tro, Chemistry: A Molecular Approach - Chap 1

Example 1.9 Convert 5.70 L to cubic inches
Sort information Given: Find: 5.70 L volume, in3 Strategize Concept Plan: Relationships: 1 mL = 1 cm3, 1 mL = 10-3 L 1 cm = 2.54 in L mL cm3 in3 Follow the concept plan to solve the problem Solution: Sig. figs. and round Round: in3 = 348 in3 Check Check: Units & magnitude are correct

Practice 1.9 How many cubic centimeters are there in 2.11 yd3?

Practice 1.9 Convert 2.11 yd3 to cubic centimeters
Sort information Given: Find: 2.11 yd3 volume, cm3 Strategize Concept Plan: Relationships: 1 yd = 36 in 1 in = 2.54 cm Follow the concept plan to solve the problem Solution: Sig. figs. and round Round: cm3 = 1.61 x 106 cm3 Check Check: Units & magnitude are correct yd3 in3 cm3

Density as a Conversion Factor
can use density as a conversion factor between mass and volume!! density of H2O = 1.0 g/mL \ 1.0 g H2O = 1 mL H2O density of Pb = 11.3 g/cm3 \ 11.3 g Pb = 1 cm3 Pb How much does 4.0 cm3 of lead weigh? = 4.0 cm3 Pb 11.3 g Pb 1 cm3 Pb 45 g Pb x Tro, Chemistry: A Molecular Approach - Chap 1

Units & magnitude are correct
Example What is the mass in kg of 173,231 L of jet fuel whose density is g/mL? Sort information Given: Find: 173,231 L density = g/mL mass, kg Strategize Concept Plan: Relationships: 1 mL = g, 1 mL = 10-3 L 1 kg = 1000 g L mL g kg Follow the concept plan to solve the problem Solution: Sig. figs. and round Round: 1.33 x 105 kg Check Check: Units & magnitude are correct

Order of Magnitude Estimations
using scientific notation focus on the exponent on 10 if the decimal part of the number is less than 5, just drop it if the decimal part of the number is greater than 5, increase the exponent on 10 by 1 multiply by adding exponents, divide by subtracting exponents Tro, Chemistry: A Molecular Approach - Chap 1

Estimate the Answer Suppose you count 1.2 x 105 atoms per second for a year. How many would you count? 1 s = 1.2 x 105  105 atoms 1 minute = 6 x 101  102 s 1 hour = 6 x 101  102 min 1 day = 24  101 hr 1 yr = 365  102 days Tro, Chemistry: A Molecular Approach - Chap 1

Problem Solving with Equations
When solving a problem involves using an equation, the concept plan involves being given all the variables except the one you want to find Solve the equation for the variable you wish to find, then substitute and compute Tro, Chemistry: A Molecular Approach - Chap 1

Using Density in Calculations
Concept Plans: m, V D m, D V V, D m Tro, Chemistry: A Molecular Approach - Chap 1

Example 1. 12 Find the density of a metal cylinder with mass 8
Example Find the density of a metal cylinder with mass 8.3 g, length 1.94 cm, and radius 0.55 cm Sort information Given: Find: m = 8.3 g l = 1.94 cm, r = 0.55 cm density, g/cm3 Strategize Concept Plan: Relationships: V = π r2 l d = m/V l, r V m, V d Follow the concept plan to solve the problem Sig. figs. and round Solution: V = π (0.55 cm)2 (1.94 cm) V = cm3 Check Check: Units & magnitude OK

Important Terms Chemistry Experiment Hypothesis Natural Law Scientific Method Theory Density Measurement Unit Accuracy Precision Systematic Error Energy Work Chemical Property Physical Property These are some of the important terms from the chapter. Make sure that you know their definitions and understand the relationships between them. Tro, Chemistry: A Molecular Approach - Chap 1

Homework You should examine and be able to answer all of the ‘Problems’…some of them (or similar questions) may be on the test To be handed in for grading: 1.38, 1.42, 1.46, 1.48, 1.52, 1.58, 1.64, 1.72, 1.84, 1.92 Due date : Home work for chapter 1 is : Due date : Tro, Chemistry: A Molecular Approach - Chap 1

Tro CHEMISTRY; A Molecular Approach

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