Module 1: Introduction to Chemistry PDF

ENSC 101 – CHEMISTRY FOR ENGINEERS I. INTRODUCTION TO CHEMISTRY INTRODUCTION This module presents an introduction to chemistry. It is hoped that you will learn about the branches...

ENSC 101 – CHEMISTRY FOR ENGINEERS I. INTRODUCTION TO CHEMISTRY INTRODUCTION This module presents an introduction to chemistry. It is hoped that you will learn about the branches of chemistry, the phases of matter and the different phase changes. You will also learn about pure substances and mixtures as well as physical and chemical properties and changes. OBJECTIVES After studying the module, you should be able to: 1. identify the different branches of chemistry and its relationship with other sciences; 2. differentiate the phases of matter and the six phase changes; 3. distinguish between pure substances and mixtures and identify mixtures as homogeneous or heterogeneous; 4. separate physical from chemical properties and label a change as chemical or physical; and 5. list evidence that can indicate a chemical change occurred. Lesson 1  BRANCHES of CHEMISTRY The Five Main Branches of Chemistry Prepared by: Engr. Gladys F. Dela Cerna  ENSC 101 – CHEMISTRY FOR ENGINEERS I. INTRODUCTION TO CHEMISTRY There are many branches of chemistry or chemistry disciplines. The five main branches are organic chemistry, inorganic chemistry, analytical chemistry, physical chemistry, and biochemistry. ORGANIC CHEMISTRY Organic chemistry involves the study of the structure, properties, and preparation of chemical compounds that consist primarily of carbon and hydrogen. Organic chemistry overlaps with many areas including Medicinal chemistry —the design, development, and synthesis of medicinal drugs. It overlaps with pharmacology (the study of drug action). Organometallic chemistry — the study of chemical compounds containing bonds between carbon and a metal. Polymer chemistry — the study of the chemistry of polymers. Physical organic chemistry — the study of the interrelationships between structure and reactivity in organic molecules. Stereochemistry — the study of the spatial arrangements of atoms in molecules and their effects on the chemical and physical properties of substances. INORGANIC CHEMISTRY Inorganic chemistry is the study of the properties and behavior of inorganic compounds. It covers all chemical compounds except organic compounds. Inorganic chemists study things such as crystal structures, minerals, metals, catalysts, and most elements in the Periodic Table. Branches of inorganic chemistry include: Bioinorganic chemistry — the study of the interaction of metal ions with living tissue, mainly through their direct effect on enzyme activity. Geochemistry — the study of the chemical composition and changes in rocks, minerals, and atmosphere of the earth or a celestial body. Nuclear chemistry — the study of radioactive substances. Organometallic chemistry — the study of chemical compounds containing bonds between carbon and a metal. Solid-state chemistry — the study of the synthesis, structure, and properties of solid materials. ANALYTICAL CHEMISTRY Analytical chemistry involves the qualitative and quantitative determination of the chemical components of substances. Examples of areas using analytical chemistry include: Forensic chemistry — the application of chemical principles, techniques, and methods to the investigation of crime. Environmental chemistry —the study of the chemical and biochemical phenomena that occur in the environment. It relies heavily on analytical chemistry and includes atmospheric, aquatic, and soil chemistry. Bioanalytical Chemistry — the examination of biological materials such as blood, urine, hair, saliva, and sweat to detect the presence of specific drugs. Prepared by: Engr. Gladys F. Dela Cerna  ENSC 101 – CHEMISTRY FOR ENGINEERS I. INTRODUCTION TO CHEMISTRY PHYSICAL CHEMISTRY Physical Chemistry —the study of the effect of chemical structure on the physical properties of a substance. Physical chemists typically study the rate of a chemical reaction, the interaction of molecules with radiation, and the calculation of structures and properties. Sub-branches of physical chemistry include: Photochemistry — the study of the chemical changes caused by light. Surface chemistry — the study of chemical reactions at surfaces of substances. It includes topics like adsorption, heterogeneous catalysis, formation of colloids, corrosion, electrode processes, and chromatography. Chemical kinetics — the study of the rates of chemical reactions, the factors affecting those rates, and the mechanism by which the reactions proceed. Quantum chemistry — the mathematical description of the motion and interaction of subatomic particles. It incorporates quantization of energy, wave-particle duality, the uncertainty principle, and their relationship to chemical processes. Spectroscopy — the use of the absorption, emission, or scattering of electromagnetic radiation by matter to study the matter or the chemical processes it undergoes. BIOCHEMISTRY Biochemistry is the study of chemical reactions that take place in living things. It tries to explain them in chemical terms. Biochemical research includes cancer and stem cell biology, infectious disease, and cell membrane and structural biology. It spans molecular biology, genetics, biochemical pharmacology, clinical biochemistry, and agricultural biochemistry. Molecular biology — the study of the interactions between the various systems of a cell, such as the different types of DNA, RNA, and protein biosynthesis. Genetics — the study of genes, heredity, and variation in living organisms. Pharmacology — the study of mechanisms of drug action and the influence of drugs on an organism. Toxicology —a sub-branch of pharmacology that studies the effects of poisons on living organisms. Clinical biochemistry — the study of the changes that disease causes in the chemical composition and biochemical processes of the body. Agricultural biochemistry — the study of the chemistry that occurs in plants, animals, and microorganisms. Thus, although there are FIVE main branches of chemistry, there are many sub-branches. There is a huge overlap between Chemistry and Biology, Medicine, Physics, Geology, and many other disciplines. Chemistry really is THE CENTRAL SCIENCE! Prepared by: Engr. Gladys F. Dela Cerna  ENSC 101 – CHEMISTRY FOR ENGINEERS I. INTRODUCTION TO CHEMISTRY Lesson 2  PHASES of MATTER Matter: Definition and the Five States of Matter Matter is the "stuff" that makes up the universe — everything that takes up space and has mass is matter. All matter is made up of atoms, which are in turn made up of protons, neutrons and electrons. Atoms come together to form molecules, which are the building blocks for all types of matter. Both atoms and molecules are held together by a form of potential energy called chemical energy. Unlike kinetic energy, which is the energy of an object in motion, potential energy is the energy stored in an object. The five phases of matter There are four natural states of matter: Solids, liquids, gases and plasma. The fifth state is the man- made Bose-Einstein condensates. 1. Solids In a solid, particles are packed tightly together so they don't move much. The electrons of each atom are constantly in motion, so the atoms have a small vibration, but they are fixed in their position. Because of this, particles in a solid have very low kinetic energy. Solids have a definite shape, as well as mass and volume, and do not conform to the shape of the container in which they are placed. Solids also have a high density, meaning that the particles are tightly packed together. 2. Liquids In a liquid, the particles are more loosely packed than in a solid and are able to flow around each other, giving the liquid an indefinite shape. Therefore, the liquid will conform to the shape of its container. Much like solids, liquids (most of which have a lower density than solids) are incredibly difficult to compress. 3. Gases In a gas, the particles have a great deal of space between them and have high kinetic energy. A gas has no definite shape or volume. If unconfined, the particles of a gas will spread out indefinitely; if confined, the gas will expand to fill its container. When a gas is put under pressure by reducing the volume of the container, the space between particles is reduced and the gas is compressed. Prepared by: Engr. Gladys F. Dela Cerna  ENSC 101 – CHEMISTRY FOR ENGINEERS I. INTRODUCTION TO CHEMISTRY 4. Plasma Plasma is not a common state of matter here on Earth, but it may be the most common state of matter in the universe. Stars are essentially superheated balls of plasma. Plasma consists of highly charged particles with extremely high kinetic energy. The noble gases (helium, neon, argon, krypton, xenon and radon) are often used to make glowing signs by using electricity to ionize them to the plasma state. 5. Bose-Einstein condensate The Bose-Einstein condensate (BEC) was created by scientists in 1995. Using a combination of lasers and magnets, Eric Cornell and Carl Weiman, scientists at the Joint Institute for Lab Astrophysics (JILA) in Boulder, Colorado, cooled a sample of rubidium to within a few degrees of absolute zero. At this extremely low temperature, molecular motion comes very close to stopping. Since there is almost no kinetic energy being transferred from one atom to another, the atoms begin to clump together. There are no longer thousands of separate atoms, just one "super atom." A BEC is used to study quantum mechanics on a macroscopic level. Light appears to slow down as it passes through a BEC, allowing scientists to study the particle/wave paradox. A BEC also has many of the properties of a superfluid, or a fluid that flows without friction. BECs are also used to simulate conditions that might exist in black holes. Changes of Phase A phase is a distinctive form of a substance, and matter can change among the phases. It may take extreme temperature, pressure or energy, but all matter can be changed. There are six distinct changes of phase which happens to different substances at different temperatures. The six changes are: Freezing: the substance changes from a liquid to a solid. Melting: the substance changes back from the solid to the liquid. Condensation: the substance changes from a gas to a liquid. Vaporization: the substance changes from a liquid to a gas. Sublimation: the substance changes directly from a solid to a gas without going through the liquid phase. Deposition: the substance changes directly from a gas to a solid without going through the liquid phase. Prepared by: Engr. Gladys F. Dela Cerna  ENSC 101 – CHEMISTRY FOR ENGINEERS I. INTRODUCTION TO CHEMISTRY Lesson 3  PURE SUBSTANCES and MIXTURES Classifying Matter We can classify matter into several categories. Two broad categories are mixtures and pure substances. A pure substance has a constant composition. All specimens of a pure substance have the same makeup and properties. A mixture is composed of two or more types of matter that can be present in varying amounts and can be separated by physical changes. Pure Substances When we speak of a pure substance, we are speaking of something that contains only one kind of matter. This can either be one single element or one single compound, but every sample of Prepared by: Engr. Gladys F. Dela Cerna  ENSC 101 – CHEMISTRY FOR ENGINEERS I. INTRODUCTION TO CHEMISTRY this substance that you examine must contain the same thing with a fixed, definite set of properties. *Note: pure oxygen gas consists of molecules but it is still considered an element, rather than a compound, as the molecules are made up of a single type of element. Compounds are made up of one or more element. Mixtures If we take two or more pure substances and mix them together, we refer to this as a mixture. Mixtures can always be separated again into component pure substances, because bonding among the atoms of the constituent substances does not occur in a mixture. Whereas a compound may have very different properties from the elements that compose it, in mixtures the substances keep their individual properties. For example, sodium is a soft shiny metal and chlorine is a pungent green gas. These two elements can combine to form the compound, sodium chloride (table salt) which is a white, crystalline solid having none of the properties of either sodium or chlorine. If, however, you mixed table salt with ground pepper, you would still be able to see the individual grains of each of them and, if you were patient, you could take tweezers and carefully separate them back into pure salt and pure pepper. Heterogeneous mixture A heterogeneous mixture is a mixture in which the composition is not uniform throughout the mixture. Vegetable soup is a heterogeneous mixture. Any given spoonful of soup will contain varying amounts of the different vegetables and other components of the soup. Homogeneous mixture/ Solution A homogeneous mixture is combination of two or more substances that are so intimately mixed that the mixture behaves as a single substance. Another word for a homogeneous mixture is solution. Thus, a combination of salt and steel wool is a heterogeneous mixture because it is easy to see which particles of the matter are salt crystals and which are steel wool. On the other hand, if you take salt crystals and dissolve them in water, it is very difficult to tell that you have more than one substance present just by looking—even if you use a powerful microscope. The salt dissolved in water is a homogeneous mixture, or a solution (See figure below). Prepared by: Engr. Gladys F. Dela Cerna  ENSC 101 – CHEMISTRY FOR ENGINEERS I. INTRODUCTION TO CHEMISTRY Types of Mixtures © Thinkstock - On the left, the combination of two substances is a heterogeneous mixture because the particles of the two components look different. On the right, the salt crystals have dissolved in the water so finely that you cannot tell that salt is present. The homogeneous mixture appears like a single substance. Examples: 1. Identify the following combinations as heterogeneous mixtures or homogenous mixtures. a. soda water (Carbon dioxide is dissolved in water.) b. a mixture of iron metal filings and sulfur powder (Both iron and sulfur are elements.) A mixture of iron filings and sulfur powder Answers: a. Because carbon dioxide is dissolved in water, we can infer from the behavior of salt crystals dissolved in water that carbon dioxide dissolved in water is (also) a homogeneous mixture. b. Assuming that the iron and sulfur are simply mixed together, it should be easy to see what is iron and what is sulfur, so this is a heterogeneous mixture. 2. Identify each substance as a compound, an element, a heterogeneous mixture, or a homogeneous mixture (solution). a. filtered tea b. freshly squeezed orange juice Prepared by: Engr. Gladys F. Dela Cerna  ENSC 101 – CHEMISTRY FOR ENGINEERS I. INTRODUCTION TO CHEMISTRY c. a compact disc d. aluminum oxide, a white powder that contains a 2:3 ratio of aluminum and oxygen atoms e. selenium Strategy: A. Decide whether a substance is chemically pure. If it is pure, the substance is either an element or a compound. If a substance can be separated into its elements, it is a compound. B. If a substance is not chemically pure, it is either a heterogeneous mixture or a homogeneous mixture. If its composition is uniform throughout, it is a homogeneous mixture. Answers: a. A) Tea is a solution of compounds in water, so it is not chemically pure. It is usually separated from tea leaves by filtration. B) Because the composition of the solution is uniform throughout, it is a homogeneous mixture. b. A) Orange juice contains particles of solid (pulp) as well as liquid; it is not chemically pure. B) Because its composition is not uniform throughout, orange juice is a heterogeneous mixture. c. A) A compact disc is a solid material that contains more than one element, with regions of different compositions visible along its edge. Hence a compact disc is not chemically pure. B) The regions of different composition indicate that a compact disc is a heterogeneous mixture. d. A) Aluminum oxide is a single, chemically pure compound. e. A) Selenium is one of the known elements. KEY TAKEAWAYS Pure substances are composed of a single element or compounds. Combinations of different substances are called mixtures. Homogeneous mixtures are mixtures of two or more compounds (or elements) that are not visually distinguishable from each other. Heterogeneous mixtures are mixtures of two or more compounds (or elements) that are visually distinguishable from one another. Prepared by: Engr. Gladys F. Dela Cerna  ENSC 101 – CHEMISTRY FOR ENGINEERS I. INTRODUCTION TO CHEMISTRY Lesson 4  PHYSICAL and CHEMICAL PROPERTIES Physical Property A physical property is a characteristic of a substance that can be observed or measured without changing the identity of the substance. Silver is a shiny metal that conducts electricity very well. It can be molded into thin sheets, a property called malleability. Salt is dull and brittle and conducts electricity when it has been dissolved into water, which it does quite easily. Physical properties of matter include color, hardness, malleability, solubility, electrical conductivity, density, melting points, and boiling points. For the elements, color does not vary much from one element to the next. Many elements are colorless, silver, or gray. Some elements do have distinctive colors: sulfur and chlorine are yellow, copper is (of course) copper-colored, and elemental bromine is red. However, density can be a very useful parameter for identifying an element. Of the materials that exist as solids at room temperature, iodine has a very low density compared to zinc, chromium, and tin. Gold has a very high density, as does platinum. Pure water, for example, has a density of 0.998 g/cm 3 at 25°C. Corn oil has a lower mass to volume ratio than water. This means that when added to water, corn oil will “float.” Hardness helps determine how an element (especially a metal) might be used. Many elements are fairly soft (silver and gold, for example) while others (such as titanium, tungsten, and chromium) are much harder. Carbon is an interesting example of hardness. In graphite, (the "lead" found in pencils) the carbon is very soft, while the carbon in a diamond is roughly seven times as hard. Pencil (left) and Diamond ring (right). Both are a form of carbon but exhibit very different physical properties. Melting and boiling points are somewhat unique identifiers, especially of compounds. In addition to giving some idea as to the identity of the compound, important information can be obtained about the purity of the material. Prepared by: Engr. Gladys F. Dela Cerna  ENSC 101 – CHEMISTRY FOR ENGINEERS I. INTRODUCTION TO CHEMISTRY Chemical Properties Chemical properties of matter describe its "potential" to undergo some chemical change or reaction by virtue of its composition. What elements, electrons, and bonding are present to give the potential for chemical change. It is quite difficult to define a chemical property without using the word "change". Eventually you should be able to look at the formula of a compound and state some chemical property. Currently this is very difficult to do, and you are not expected to be able to do it. For example, hydrogen has the potential to ignite and explode given the right conditions - this is a chemical property. Metals in general have they chemical property of reacting with an acid. Zinc reacts with hydrochloric acid to produce hydrogen gas - this is a chemical property. Heavy rust on the links of a chain near the Golden Gate Bridge in San Francisco; it was continuously exposed to moisture and salt spray, causing surface breakdown, cracking, and flaking of the metal. Image used with permission A chemical property of iron is that it can combine with oxygen to form iron oxide, the chemical name of rust. The more general term for rusting and other similar processes is corrosion. Other terms that are commonly used in descriptions of chemical changes are burn, rot, explode, decompose, and ferment. Chemical properties are very useful in identifying substances. However, unlike physical properties, chemical properties can only be observed as the substance is in the process of being changed into a different substance. Contrasting Physical and Chemical Properties Example: Which of the following is a chemical property of iron? a. Iron corrodes in moist air b. Density = 7.874 g/cm3 c. Iron is soft when pure. d. Iron melts at 1808 K. Answer: Iron corrodes in moist air is the only chemical property of iron from the list. The other three are all physical properties. Prepared by: Engr. Gladys F. Dela Cerna  ENSC 101 – CHEMISTRY FOR ENGINEERS I. INTRODUCTION TO CHEMISTRY Lesson 5  PHYSICAL and CHEMICAL CHANGES Physical Change Physical changes are changes in which no bonds are broken or formed. This means that the same types of compounds or elements that were there at the beginning of the change are there at the end of the change. Because the ending materials are the same as the beginning materials, the properties (such as color, boiling point, etc.) will also be the same. Physical changes involve moving molecules around, but not changing them. Some types of physical changes include: Changes of state (changes from a solid to a liquid or a gas and vice versa) Separation of a mixture Ice Melting is a physical change. When liquid water (H2O) Physical deformation (cutting, denting, freezes into a solid state (ice), its appearance changed; stretching) however, this change is only physical as the composition of the constituent molecules is the same: 11.19% Making solutions (special kinds of hydrogen and 88.81% oxygen by mass. mixtures) As an ice cube melts, its shape changes as it acquires the ability to flow. However, its composition does not change. Melting is an example of a physical change. A physical change is a change to a sample of matter in which some properties of the material change, but the identity of the matter does not. When we heat the liquid water, it changes to water vapor. But even though the physical properties have changed, the molecules are the same as before. We still have each water molecule containing two hydrogen atoms and one oxygen atom covalently bonded. When you have a jar containing a mixture of pennies and nickels and you sort the mixture so that you have one pile of pennies and another pile of nickels, you have not altered the identity of either the pennies or the nickels - you've merely separated them into two groups. This would be an example of a physical change. Similarly, if you have a piece of paper, you don't change it into something other than a piece of paper by ripping it up. What was paper before you started tearing is still paper when you're done. Again, this is an example of a physical change. Physical changes can further be classified as reversible or irreversible. The melted ice cube may be refrozen, so melting is a reversible physical change. Physical changes that involve a change of state are all reversible. Other changes of state include vaporization (liquid to gas), freezing (liquid to solid), and condensation (gas to liquid). Dissolving is also a reversible Prepared by: Engr. Gladys F. Dela Cerna  ENSC 101 – CHEMISTRY FOR ENGINEERS I. INTRODUCTION TO CHEMISTRY physical change. When salt is dissolved into water, the salt is said to have entered the aqueous state. The salt may be regained by boiling off the water, leaving the salt behind. Chemical Change Chemical changes occur when bonds are broken and/or formed between molecules or atoms. This means that one substance with a certain set of properties (such as melting point, color, taste, etc.) is turned into a different substance with different properties. Chemical changes are frequently harder to reverse than physical changes. One good example of a chemical change is burning a candle. The act of burning paper results in the formation of new chemicals (carbon dioxide and water, to be exact) from the burning of the wax. Another example of a chemical change is what occurs when natural gas is burned in your furnace. This time, on the left we have a molecule of methane, CH4CH4, and two molecules of oxygen, O2O2, while on the right we have two molecules of water, H2OH2O, and one molecule of carbon dioxide, CO2CO2. In this case, not only has the appearance changed, but the structure of the molecules has also changed. The new substances do not have the same chemical properties as the original ones. Therefore, this Burning of wax to generate water and carbon dioxide is is a chemical change. a chemical reaction. Image used with permission We can't actually see molecules breaking and forming bonds, although that's what defines chemical changes. We must make other observations to indicate that a chemical change has happened. Some of the evidence for chemical change will involve the energy changes that occur in chemical changes, but some evidence involves the fact that new substances with different properties are formed in a chemical change. Observations that help to indicate chemical change include: Temperature changes (either the temperature increases or decreases) Light is given off Unexpected color changes (a substance with a different color is made, rather than just mixing the original colors together) Bubbles are formed (but the substance is not boiling - you made a substance that is a gas at the temperature of the beginning materials, instead of a liquid) Different smell or taste (do not taste your chemistry experiments, though!) A solid forms if two clear liquids are mixed (look for floaties - technically called a precipitate) Prepared by: Engr. Gladys F. Dela Cerna  ENSC 101 – CHEMISTRY FOR ENGINEERS I. INTRODUCTION TO CHEMISTRY Example: Label each of the following changes as a physical or chemical change. Give evidence to support your answer. a. Boiling water b. A nail rusting c. A green solution and colorless solution are mixed. The resulting mixture is a solution with a pale green color. d. Two colorless solutions are mixed. The resulting mixture has a yellow precipitate. Answers: a. Physical: boiling and melting are physical changes. When water boils no bonds are broken or formed. The change could be written: H2O (l) → H2O (g) b. Chemical: The dark grey nail changes color to form an orange flaky substance (the rust); this must be a chemical change. Color changes indicate chemical change. The following reaction occurs: Fe + O2 → Fe2O3 c. Physical: because none of the properties changed, this is a physical change. The green mixture is still green, and the colorless solution is still colorless. They have just been spread together. No color change occurred or other evidence of chemical change. d. Chemical: the formation of a precipitate and the color change from colorless to yellow indicate a chemical change. Prepared by: Engr. Gladys F. Dela Cerna