General Chemistry Reviewer, Lecture notes of Chemistry

Download General Chemistry Reviewer and more Lecture notes Chemistry in PDF only on Docsity! LESSON 1: MATTER AND ITS PROPERTIES MATTER  Is anything that has mass and volume PROPERTIES OF MATTER 1. VOLUME o The amount of three-dimensional space in a matter 2. MASS o Is a measure of the amount of matter GAS  A gas is made up of particles that are far apart from each other, which can be pushed closer towards each other. SOLID  A solid is made up of particles which are compact, so that it is no longer possible to push these particles closer to each other PARTICLES OF MATTER MOLECULES  Is the smallest particle in a chemical element or compound that has the chemical properties of the elements or compound  Are made of atoms that are held together by chemical bonds . These bonds form as a result of the sharing or exchange of electrons among atoms.  Can vary gravity size and complexity  The element Helium is a one-atom molecule  Some molecules consist of two atoms of the same elements ATOMS  Are the basic unit of matter and the defining structure of elements  Are made up of three particles, protons (+) neutrons and electrons (-) which are composed of even smaller particles such as quarks IONS  Is a charged atom or molecule. It is changed because the number of electrons do not equal the number of protons in the atom or molecule  An atom can acquire a positive charge or a negative charge dependend on whether the number of electrons in an atom is greater or less than the number of protons in the atom  If the atom has more electrons than protons it is a negative ion or ANION  If it has more protons than electrons it is a positive ion or CATION LESSON 2: STATES OF MATTER (SOLID, LIQUID, GAS) Kinetic Molecular Theory of Matter  Helps us to understand other propeties of matter a. All matter is composed of particles called atom (in element) and molecules (in compounds) b. These are spaces between the particles c. The particles of matter are in constant motion d. Each substance has unique particles that are different from other substances e. The particles are held together by electric forces SOLID  Particles are packed tightly together so they are unable to move about very much  When heated, a solid expands but only slightly  Particles of solid have very low kinetic energy  The electrons of each atoms are in motion, so the atoms have a small vibration, but they are fixed in their position  Solids have a definite shape. They do not conform to the shape of the container in where they are placed  They also have a definite volume. It is important to understand that a solid is not defined by its RIGIDITY or HARDNESS 2 MAIN CATEGORIES OF SOLID 1. AMORPHOUS  An amorphous solid is one that loses its shape, under certain circumstances  Molecules are randomly arranged  Also called “pseudo solids”  Examples: Wax, rubber, glass, cotton candy 2. CRYSTALLINE  Molecules are uniformly arranged  Also called “true solids”  Examples: common table salts LIQUID  The particles have more kinetic energy than those in solid  The liquid particles are not held in a regular arrangement, but are still very close to each other so liquids have definite volume  Liquids like solid cannot be compressed.  Particles of a liquid have just enough room to flow around each other, so liquids have an indefinite shape  A liquid will change shape to conform to its container  Force is spread evenly throughout the liquid, so when an object is placed in a liquid, the liquid particles are displaced by the object (Buoyancy)  Like solids, liquids tend to expands when they are heated BIG CONCEPT  A liquids volume is constant regardless od the size and shape of the container in which the liquid is held the volume of the liquid remains the same GAS  Gas particles have a great deal of space between them and have high kinetic energy  If unconfined the particles of a gas will spread out indefinitely; if confined, the gas will expand to fill its containers  When a gas is put under pressure by reducing the volume of the container, the space between particles is reduced and the pressure exerted by their collisions increases  If the volume of the container is held constant, but the temperature if the gas increases, then the pressure will also increase  Gas particles have enough kinetic energy to overcome intermolecular forces that hold solids and liquids together, thus a gas has no definite volume and no definite shape LESSON 3: PROPERTIES OF MATTER (PHYSICAL, CHEMICAL PROPERTY) PHYSICAL PROPERTY 1. Is a characteristics of matter that can be observed and measured without matter changing to a different substance (or changing the sample’s composition) 2. Generally, physical properties are things you can see, hear, smell, or feel with your senses 1. See 2. Touch 3. Hear 4. Smell 5. Temperature 6. Weight 7. Density 8. Color 9. Odor 10. Hardness 11. Maleability  Ability of matter to beaten into thin sheets 12. Ductility  Ability of matter to be drown into thin wires 13. Luster 14. Mass 15. Volume 16. Bouyancy o Ability of liquid to let objects flow 17. Viscosity o The resistance to flow 18. Melting point 19. Freezing point 20. Boiling point Solubility  Ability to dissolve in other substances Conductivity  Ability to conduct heat or electricity a. Heat/Thermal Conductivity b. Elecetrical Conductivity APPLICATIONS OF PHYSICAL PROPERTIES  Hardness a. Diamond b. Talc  Freezing and Boiling Point a. Anti freeze  Ability to conduct heat or electricity a. Cooking Pan/Pot b. Cooking Untensils c. Copper  Ability to dissolve in other substances a. Sand in water b. Salt in water STRENGTH  The strength of a material refers to its ability to support a heavy load without breaking or tearing  Example: Steel vs Paper HARDNESS o Burned wood becomes ash, carbon dioxide, and water o When exposed to water, iron becomes a mixture of several hydrated iron oxides and hyrdoxides o Yeast carries out fermentation to produce alcohol from sugar “The new substances do not have the same chemical properties as the original ones. Therefore, this is a chemical change.”  We can’t actually see molecules breaking and forming bonds, although that’s what defines chemical changes  We have to make other observations to indicate that a chemical change has happened Observations that help to indicate chemical change include:  Temperature changes (either 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) LESSON 6: PURE SUBSTANCE AND MIXTURES PURE SUBSTANCE  Chemical substances are often called “pure” to set them apart from mixtures o Pure Water; it always has the same properties and the same ratio of hydrogen to oxygen whether it is isolated from a river or made in a laboratory o Diamond (carbon), gold, table salt (sodium chloride), and refine sugar (sucrose)  Cannot be separated into 2 or more substances by physical (such as cryztallization or distillation) or mechanical means (such as sifting, filtering, or using a magnet) o Distilling pure water does NOT separate water into simpler substances which would be the elements hydrogen (H) and oxygen (O), it only produces water vapor (the same substance but in a different phase or state)  Is homogeneous, that is, has uniform composition throughout the whole sample o This means that a pure substance will have a constant appearance, color, density, melting point and boiling point throughout the sample o It also means that if you take a small sample of the original pure substance, the sample will undergo the same chemical reactions as the original substance  If you broke a piece of pure elemental iron (Fe) up into smaller pieces, then each piece will  Have the same metallic luster as each other and the original sample  Have the same dark-grey color as each other and the original sample  Have the same density as each other and the original sample  Display the same magnetic behavior, attraction to a magnet, as each other and the original sample  Have the same melting point and boiling point as each other and the original sample  Produce the same odorless gas, hydrogen gas, when acid is added to the samples  Has properties that are constant throughout the whole sample o A pure substance has a SHARP MELTING POINT (melts at one temperature) and a SHARP BOILING POINT (boils at one temperature)  Has constant chemical composition o This means that a pure substance can be either an element or a compound  The element sulfur (S) is a pure substance, it is made up ONLY of sulfur atoms  The elements of IRON (Fe) is a pure substance, it is made up ONLY of iron atoms  The compound iron is a (FeS) is a pure substance, it is always made up of 1 iron atom chemically bonded to 1 sulfur atom  The element Hydrogen exists as H2 molecules and is a pure substance, it is made up of 2 hydrogen atoms chemically bonded to each other  The element OXYGEN exists as O2 molecules and is a pure substance, it is made up of 2 oxygen atoms chemically bonded to each other ELEMENT  Is a chemical substance that is made up of a particular kind of atom and hence cannot be broken down or transformed by a chemical reaction into a different element  All atoms of an element have the same number of protons, though they may have different numbers of neutron and electrons  Any substance that contains only one kind of an atom is known as an element o Because atoms cannot be created or destroyed in a chemical reaction, elements such as phosphorus (P4) or sulfur (S4) cannot be broken down into simpler substances by these reactions  The elements can be divided into three categories that have characteristic properties; metals, nonmetals, and semimetals o Metals which are found on the left and toward the bottom of the peridic table o Nonmetals are clustered in the upper right corner of the periodic table o Semimetals can be found along the dividing line between the metals and the nonmetals COMPOUND  A pure chemical compound is a chemical substance that is composed of a particular set of molecules or ions that are chemically bonded  Two or more elements combined into one substance through a chemical reaction, such as water, form a chemical compound  Elements combine to form chemical compounds that are often divided into two categories o Metals often react with nonmetals to form ionic compounds o Nonmetals combine with each other to form covalent compounds COMPOUND (IONIC)  These compounds are composed of positive and negative ions formed by adding or subtracting electrons from neutral atoms and molecules 2Na + Cl2 2NaCl COMPOUND (COVALENT)  Exist as neutral molecules 2H2 + O2 2H2O BIG CONCEPT ALL compounds are substances, but NOT all subances are compounds. Because some substances are elements. COMPOUND  A chemical compound can be either atoms bonded together in molecules or crystals in which atoms, molecules or ions form a crystalline lattice. o Compounds made primarily of carbon and hydrogen atoms are called organic compounds, all others are called inorganic compounds o Compounds containing bonds between carbon and a metal are called organometallic compounds  When the elements are joined, the atoms lose their individual properties and have different properties from the elements they are composed of o A chemical formula is used a quick way to show the composition of compounds o Letters, numbers, and symbols are used to represent elements and the number of elements in each compound MIXTURES  A material system made up of two or more different substances, which are mixed but NOT combined chemically  Refers to the physical combination of two or more substances in which the identities of the individual substances are retained o Mixtures take the form of alloys, solutions, suspensions, and colloids.  A mixture displays the properties of the pure substances making it up o If you grind up some metallic iron (Fe) and yellow sulfur (S) up in a mortar and pestle this is a mixture because the iron is still a dark-grey color with metallic luster that is attracted to a magnet and will react with acid to produce hydrogen gas o Sulfur is still a dull yellow that is not attracted to a magnet and will not react with acid  A mixture can be separated into 2 or more substances by physical or mechanical means because each pure substance retain its own properties o If you grind up some metallic iron (Fe) and yellow sulfur (S) up in a mortar and pestle this is a mixture because you can separate the magnetic iron from the non-magnetic sulfur using a magnet METHODS SEPARATING THE COMPONENTS IN A MIXTURE SEPARATION TECHNIQUE PROPERTY USED FOR SEPARATION EXAMPLE Sifting (sieving) Particle size Alluvial gold is separated from smaller soil particles using a sieve Visual Sorting Colour Gold nuggets can be separated from crushed rock on the basis of color Magnetic Attraction Magnetism Magnetic iron can be separated from non- magnetic sulfur using a magnet Decanting Density and Solubility Liquid Water can be poured (decanted) off insoluble solid sand sediment Less dense “liquid” oil can be poured (decanted) off more dense liquid water Filtration Solubility Insoluble solid calcium carbonate can be separated from liquid water by filtration Evaporation Solubility and Boiling Point Soluble salts like sodium chloride in sea water can be separated from water by evaporation Crystallization (crystallisation) Solubility Slightly soluble copper sulfate can be separated from water by crystallization Distillation Boiling Point Liquid ethanol (ethyl alcohol) can be separated from liquid water by distillation because ethanol has a lower boiling point than water Kerosene, diesel and petrol can be separated from crude oil by distilltion because each of these substancs has a different boiling point MIXTURES  Has a composition that can be varied by changing the proportion of pure substances making it up o If you grind up some metallic iron (Fe) and yellow sulfur (S) up in a mortar and pestle this is a mixture because you change the proportions (relative amount) of iron and sulfur that you use o You could use equal amounts of iron and sulfur to make the mixture, or you could use more iron and less sulfur, or you could use more sulfur and less iron HETEROGENEOUS MIXTURE  One with a non-uniform composition throughout the sample o Rocks from which metals are extracted (ores) are hetergeneous substances because the composition of the rock can vary o One sample of the ore may contain a larger percentage of the metal than another sample within the same rock formation o Muddy water such as you find in a lake is a mixture composed of fine clay particles suspended in water as well as dissolved salts and micro- organisms o The composition of this mixture near the surface of the lake will be different to the composition of the mixture near the bottom of the lake o Because the mixture in the lake does not have a uniform composition