Physical Properties A trait we can observe w/o changing the identity of the substance. EXAMPLES: Color Shape Dimensions (size) Texture Taste Temperature Melting Point Density Smell Freezing Point Mass Chemical Properties A trait we can observe by changing the identity of the substance. EXAMPLES: Flammability Decomposable Digestible Toxicity Ability to Oxidization Reactivity/Inert Physical Change A change that affects only physical properties and does not change the identity of the substance. EXAMPLES: Rip Crumble Wet Throw Draw Fold Kick Mix Chemical Change A change that alters the identity of the substance. EXAMPLES: Eating/Digesting Burning React w/ acid or anything Decompose Oxidization Elements, Compounds, and Mixtures Element: substances that cannot be separated by chemical or physical means. Atom: smallest unit of an element. Compound: substance made of 2 or more elements. It can only be separated by chemical means. Molecule: smallest unit of a compound. Mixture: A combination of substances that are not chemically combined. Can be separated by physical means. Homogeneous: looks the same throughout. Heterogeneous: composed of different parts. Density A ratio of mass to volume. D= m/v D=Density V=Volume M=Mass g/ml=g/cm^3 milliliters=cm^3 grams Example Problem: Density A rock has a mass of 8g. When Bob puts it in a graduated cylinder it displaces 4L of water. What is the density? ANSWER D=M/V D=8g/4L D=2L Scientific Notation A way of writing numbers that are too big or too small to be conveniently written in decimal form. EXAMPLES: 300 = 3×102 6,720,000,000 = 6.72×109 Sig Figs Multiplication and Division Rules: The number of sig figs in your answer is same as the least number of sig figs in measurements. EX: find the area from these measurements. 505cm long = 3 sig figs 10cm wide = 1 sig fig A=LxW A= 505 x 10 = 5050cm2 A= 5,000cm2 the your Extra Practice Find the rate of measurement. 250.0mL 0.25s ANSWER Find the rate of measurements. 250.0 mL = 3 sig figs 0.25s = 2 sig figs 250.0/0.25 = 1000mL/s 1.0 x 103 Sig Figs Continued Addition and Subtraction Rules: The estimated number in your answer is located in the same place value column as the estimated number in the measurement’s that is farthest to the left. EX: 101.0g + 10.5g 111.5g 112 g Extra Practice 212.25C and 12.3C ANSWER 212.25C + 12.3C 199.95C 200.0C Accuracy/Precision Accuracy/Precision Continued the accuracy of a measurement system is the degree of closeness of measurements of a quantity to that quantity's actual value. The precision of a measurement system, also called reproducibility or repeatability, is the degree to which repeated measurements under unchanged conditions show the same results. Quantitative/Qualitative Quantitative: Is expressed or related to in terms of quantity as in numbers. Qualitative: Related to or involving quality or kind. Ionic Compound Occurs between One Metal and Non-Metal Crystilanial Solids (Made of Ions) High Melting and Boiling points Conduct with electricity when melted No Definite shape Covalent Compound Occurs Between Two Metals Gases, Liquids, Soft Solids (Made of Molecules) Low Melting and Boiling points Poor electrical conductors Define Shape Periodic Table To the left of the red line are non-metal To the right of the red line are metals Example …is which type of bond? 1. NaBr 2. HCL 3. AgCL 4. C2S Answers 1. Ionic Bond- Na is a non-metal, Br is a Metal 2. Ionic Bond- H is a non-metal, Cl is a metal 3. Ionic Bond- Ag is a non-metal, Cl is a metal 4. Covalent Bond- C is a metal, S is a metal To Tell The Difference Look at periodic table Locate your elements Look for the stair case in the periodic table Under elements B,SI,AS,TE,AT Isotopes An isotope is an atoms with the same number of protons, but differing numbers of neutrons Isotopes are different forms of a single element Different Atomic Mass How To Calculate Average Atomic Mass 1. Convert the percentages into decimals. (This percentage is known as its relative abundance or percent abundance) 2. Multiply the percentage of each isotope by its respective mass 3. Add the numbers from step two together Example mass number exact weight percent abundance 12 12.000000 98.90 13 13.003355 1.10 Answer This is the solution for carbon: (12.000000) (0.9890) + (13.003355) (0.0110) = 12.011 amu Basics Find your element on the Period Table element's atomic number and atomic weight. atomic number is the number in the upper left corner atomic weight is the number on the bottom Protons and Electrons The atomic number is the number of protons in an atom of an element. krypton's atomic number is 36, so an atom of krypton has 36 protons Electrons have the same quantity as protons Neutrons Mass Number = (Number of Protons) + (Number of Neutrons) For krypton, this equation becomes: 84 = (Number of Protons) + (Number of Neutrons) 84 = 36 + (Number of Neutrons) NUETRONS = 48 Summary For any element: Number of Protons = Atomic Number Number of Electrons = Number of Protons = Atomic Number Number of Neutrons = Mass Number - Atomic Number Ions Ions are formed when an atom gains or loses electrons and gets charged If an atom gains electrons, number of electrons are higher than protons an atom gets negatively charged Similarly if an atom loses electrons the total number of protons become more than the number of electrons atom becomes positively charged What is an ion? Ion electrically charged atom or atom group: an atom or group of atoms that has acquired an electric charge by losing or gaining one or more electrons Knowing the charge So… Determine the charge of each element when present in an ionic compound. Use the table above to determine these charges. For example, O = -2, Rb = +1. Use the appropriate number of each ions such that: For example, if magnesium (Mg) and bromine (Br) are mixed: Metal (Mg) + Non-metal (Br) IS an ionic compound. Mg ⇒ Mg+2 and Br ⇒ Br-1 For the final steps: The sum of all charges adds up to zero. The simplest ratio of ions is used. One +2 ion is exactly balanced by two -1 ions. 2:1 is the simplest possible ratio. Thus, the formula of the ionic compound formed is MgBr2 Alpha There Alpha are three primary types of radiation: - these are fast moving helium atoms. They have high energy, but due to their large mass, they are stopped by just a few inches of air, or a piece of paper. Beta These are fast moving electrons. Since electrons are lighter than helium atoms, they are able to penetrate further, through several feet of air, or several millimeters of plastic or less of very light metals. Gamma Gamma - these are photons, just like light, except of much higher energy, X-Rays and gamma rays are really the same thing, the difference is how they were produced. Depending on their energy, they can be stopped by a thin piece of aluminum foil, or they can penetrate several inches of lead Review A nuclear reaction can be described by an equation, which must be balanced. The symbol for an atom or atomic particle includes the symbol of the element, the mass number, and the atomic number. The mass number, which describes the number of protons and neutrons, is attached at the upper right of the symbol. The atomic number, which describes the number of protons in the nucleus, is attached at the lower left of the symbol Electron Configurations Diagram way/ Orbital notation 1.List all of the orbitals with boxes 2.Find out how many electrons are in the element 3. Electrons fill the lowest energy levels first (follow diagonal rule) 4.Reminder* Only 2 electrons fit into a degenerate orbital Long way/List way 1.Write out the orbitals 2.Depending on the orbital write the amount of electrons in the exponent 3.Do this until your configuration is complete 4.Reminder * S orbital- up to 2 electrons, P orbital- up to 6, D orbital- up to 10, F orbital- up to 14 Noble gas notation 1.Refer to noble gas before element 2.Write noble gas in brackets 3.Figure out next orbital and fill like usual Sample Problem: Be- Beryllium Write the: Orbital Notation List way Noble gas notation Answers to Sample Problem: Orbital Notation: 2s 1s Electron Configuration: 1s^2 2s^2 Noble Gas: [He]2s^2 Wavelength, Energy & Frequency Calculations Wavelength- distance from crest to crest of a wave, one full cycle of a wave-measured in meters Frequency- how often a wave passes per second-- measured in 1/s per second As wavelength gets smaller, wave frequency gets larger Equation: c= speed of light= 3.0x 10^8 m/s Energy of a wave is related to its frequency: E= energy in joules h= plank's constant= 6.626 x 10^-34 Joules/second Sample Problem: Ex. A light at a stoplight has a wavelength of 5m 1. What is the frequency of light? 2. What is the energy of light? Answers to Sample Problem: Answers 1. wavelength= speed/frequency 5 m= 3.0 x 10^-8 m/s ___________ frequency frequency= 3.08 x 10^-8/ 5 frequency= 6.16 x 10^-9 1/s 2. E= hv h= 6.6 x 10^-34 J x S E= (6.6 x 10^-34)(6.16 x 10^-9) E= 4.07 x 10^-42 J Trends Electronegativity-chemical property describing tendency of an atom to attract electrons to itself, which is affected by both its atomic number and the distance that its valence electrons reside from the charged nucleus. Ionization Energy- describes the amount of energy required to remove an electron from the atom or molecule. Atomic Radius- measure of the size of an element's atoms. Electronegativity, Ionization Energy & Atomic Radius Trends Periodic Table Families and Periods Periods- go across the table; there are 7 Groups- go vertically down the table; 8 are classified Families- represent elements of the same nature ex. group 8 is called the Noble Gas family because all of these elements have something in common, they all have complete valence shells Valence Electron trends on periodic table The Valence Electron trends show the amount of valence electrons in each element. Each column has a different number of valence electrons. Transition Metals Ion Trends on the Periodic Table The Ion trends on the periodic table show the charge of each element on the periodic table. Each column has a different charge. Ion Trends 1) 2) Name the 1st element written in the formula Use a prefix to tell how many we have 1) Mono 2) Di 3) Tri 4) Tetra 5) Penta 6) Hexa 7) Hecta 8) Octa 9) Nona 10) Deca Naming Covalent Compounds 3) Name the 2nd element, change the ending to -ide 4) Add a prefix to tell how many ◦ ◦ ◦ ◦ ◦ CO- Carbon Monoxide CO₂- Carbon Dioxide SO₃- Sulfur Trioxide H₂O- Dihydrogen Oxide S₆F₂- Hexasulfur Diflouride Naming Covalent Compounds Cont. 1) 2) Name the cation (First element in compound) Is the cation a transition metal 1) If yes, use a roman numeral to tell the change 2) If no, move on Name the anion Change the ending to –ide unless it’s a polyatomic ion Ex. 1) Cu₂O₃Copper III Oxide Ex. 2) Na₃PSodium Phosphide 3) 4) Naming Ionic Compounds Hydrogen ChloridePut anion root in formula Hydro_ic acidHydrochloric Acid Hydrogen ChloratePut anion root into formula ___ic acid Chloric Acid Hydrogen Chlorite Put anion root into formula ___ous acid Chlorous acid Naming Acids CuCl₂•4H₂O CuCl₂ Name normal 4H₂O Name the Prefix Copper II Chlorine • Tetra Hydrate Naming Hydrated Crystals 5 types of chemical reactions • Synthesis: 2Cu+O2 2CuO • • Decomposition: MgCl2Mg+Cl2 • • The single element is switched with the “ “ from the compound Double replacement: MgCl2+CuOMgO+CuCl2 • • The Compound decomposes into two elements Single replacement: MgCl2+CuCuCl2+Mg • • The two elements combine One element from each compound is switched Combustion: CH3OH+O2CO2+H2O • Hydrocarbon + oxygen = Carbon dioxide+ water Predicting Products • If there are two individual elements as the reactants, The reaction will be synthesis. – The product will be a compound. • If the reactant is a compound, the reaction will be decomposition. – The product will be two separate elements. • If the reactants are a compound and a single element, the element will switch with one of the elements in the compound. The reaction will be single replacement. – • The product will be a new element and a new compound If the reactants are two compounds (respectively) an element from each compound will switch. The reaction will be double replacement. – The product will be two new compounds. • If the reactants are a hydrocarbon and an oxygen, the reaction will be combustion. – The product will be carbon dioxide and water. Law of Conservation of Matter • The law of conservation of matter states that matter cannot be created or destroyed, only transferred. – This is why we must balance equations. Balancing Equations • When balancing equations, you must have the same amount of each element on either side of the reaction. – __Mg+__O2__MgO • There is too much O and too little Mg and MgO, so this equation must be balanced to follow the law of conservation of matter • Add coefficients where needed – 2 Mg+O22MgO Balancing Equations • There are 7 diatonic elements. • When listed alone, these elements always occur with the subscript of 2 • The elements are Br2, I2, N2, Cl2, H2, O2 and F2. – These can be remembered using the word BrINClHOF. Net Ionic Equations • First start by writing an ionic equation – This includes aqueous substances that dissociate into ions – Zn(s)+CuSO4(aq)ZnSO4(aq)+Cu(s) • The aqueous substances dissociate – Zn(s)+Cu+2 (aq) +SO4-2(aq)Zn=2 (aq) +SO42(aq)+Cu(s) • (aq)=aqueous, (s)=solid, (l )=liquid • Remember to add charges Net Ionic Equations • Eliminate the substances that are the same on either side of the reaction (the spectator ions) – Zn(s)+Cu+2(aq) +SO4-2(aq)Zn+2(aq) +SO42(aq)+Cu(s) – Zn(s)+C+2(aq)Zn(s)+Cu(s) • Above is the net ionic equation since the spectator ions have been removed Factor Label Method • The factor-label method was made to keep track of units in conversion problems. In the method, conversion factors are set up in fraction form. To get the unit you want, you put it on the top of the fraction next to it. You put the unit on the bottom that you are trying to get rid of. Factor Label Method Formulas Factor Label Method Examples Molar Mass Molar Mass Example Empirical Formula • An empirical formula is the lowest term ratio of elements • Its not always the true formula • When given the % composition, you can find the empirical formula • • • • Step 1: % to mass Step 2: Mass to Moles Step 3: Divide by small Step 4: Multiply till whole Empirical Formula Examples Molecular Formulas • The ‘true’ formulas • Not in lowest terms 1. 2. 3. 4. Get atomic mass Multiply by number of subscript Add numbers together Divide by molecular mass Molecular Formula Example Percent Composition Mole Ratios • The ratio between the amounts in moles of any two compounds involved in a chemical reaction. • Used as conversion factors between products and reactants in many chemistry problems. • Example: 2 H2(g) + O2(g) → 2 H2O(g) The mole ratio between O2 and H2O is 1:2. For every 1 mole of O2 used, 2 moles of H2O are formed. The mole ratio between H2 and H2O is 1:1. For every two moles of H2 used, 2 moles of H2O is formed. Stoichiometry • • • • The part of chemistry that studies amounts of substances that are involved in reactions Helps you figure out how much of a compound you will need, or how much you started with. To solve: 1.Balance the equation. 2.Convert units of a given substance to moles. 3.Using the mole ratio, calculate the moles of substance yielded by the reaction. 4.Convert moles of wanted substance to desired units. Ex: 2Mg + O2 2MgO If you have 1.2 moles of Mg, how many moles of O2 will you get? 1.2 mol Mg x O2/2Mg = .6 mol O2 Limiting and Excess Reactants • If you have more than needed, you have excess. • If you need more than you have, you have limiting. • Example: 2Al2O3+3C 3CO2+4Al If 2.3 g AlO3 and 3.2 g of C mix, which is the limiting and which is the excess? 2.3 g AlO3 x 1 mol/101.96 g = .02 mol Al2O3 (have) 3.2 g C x 1 mol/12.01 g = .27 mol C .02 x 3C/2Al2O3 = .03 mol C (need) • Excess : C • Limiting: Al2O3 Theoretical Yield • • • The quantity of a product obtained from the complete conversion of the limiting reactant in a chemical reaction. Commonly expressed in grams or moles To calculate: 1. Use the molar mass of your reactant to convert grams of your reactant to moles. 2. Use the mole ratio between reactant and product to convert moles reactant to moles product. 3. Use the molar mass of the product to convert moles product to grams of product. Theoretical yield (cont.) • Na2S(aq) + 2 AgNO3(aq) → Ag2S(s) + 2 NaNO3(aq) • How many grams of Ag2S will form when 3.94 g of AgNO3 and an excess of Na2S are reacted together? Atomic Atomic Atomic Atomic Atomic Atomic Atomic Atomic Atomic Atomic weight weight weight weight weight weight weight weight weight weight of of of of of of of of of of Ag = 107.87 g N = 14 g O = 16 g S = 32.01 g AgNO3 = (107.87 g) + (14.01 g) + 3(16.00 g) AgNO3 = 107.87 g + 14.01 g + 48.00 g AgNO3 = 169.88 g Ag2S = 2(107.87 g) + 32.01 g Ag2S = 215.74 g + 32.01 g Ag2S = 247.75 g • Two moles of AgNO3 is needed to produce one mole of Ag2S. Theoretical yield (cont.) • The excess of Na2S means all of the 3.94 g of AgNO3 will be used to complete the reaction. grams Ag2S = 3.94 g AgNO3 x 1 mol AgNO3/169.88 g AgNO3 x 1 mol Ag2S/2 mol AgNO3 x 247.75 g Ag2S/1 mol Ag2S • 2.87 g of Ag2S will be produced from 3.94 g of AgNO3. Percent yield • To find percent yield: 1. Balance the chemical equation 2. Find the limiting reagent 3. Find the theoretical yield 4. Find the actual yield 5. Find the percentage yield • Percent yield = mass of actual yield/mass of theoretical yield x 100 KINETIC MOLECULAR THEORY (COLLISION THEORY) Gas particles exhibit constant random motion Collisions happen All collisions are perfectly elastic (can bounce off each other) What Collisions Mean in the Real World Collisions between molecules of gas are what creates air pressure The more collisions that occur, the more pressure is excited All gas particles move in straight lines, but they bounce off anything they collide with As the temperature increases the particles move faster, and more collisions occur, that increases the pressure As you increases the number of particles, the number of collisions increases, which increases the pressure ABSOLUTE ZERO AND STP Absolute ZeroAbsolute zero is the point where no more heat can be removed from a system, according to the absolute or thermodynamic temperature scale. 0 K or -273.15°C. STP0˚C 1 atm 273.15 K 101,325 Pa PRESSURE CONVERSIONS Pressure is Usually Measured in: Conversions: Atmosphere (atm) Bar (Bar) Pascals (Pa) Millimeters of Mercury (mmHg) Torr (torr) 1 atm=101325 Pa 1 bar= 100025 Pa 1 torr= 133.32 Pa 1mmHg= 133.32 Pa 1mmHg= 1 torr Practice: 14.7KPa= _______ atm 14.7KPa*1000Pa/1KPa=14700Pa BOYLE’S GAS LAW A relationship between pressure and volume Inverse relationship: When pressure goes up, volume goes down. When volume goes up, pressure goes down PV=P2V2 Practice problem: A balloon with a volume of 2.0 L is filled with a gas at 3 atmospheres. If the pressure is reduced to 0.5 atmospheres without a change in temperature, what would be the volume of the balloon? V1 = 2.0 L P1 = 3 atm P2 = 0.5 atm V2 = (2.0 L)(3 atm)/(0.5 atm) Answer= 12L CHARLES’S GAS LAW A relationship between volume and temperature When temperature goes up, volume goes up When temperature goes down, volume goes down Direct relationship V/T=V2/T2 Practice problem: Given 300.0 mL of a gas at 17.0 °C. What is its volume at 10.0 °C? (300.0) / (290.0 K) = (x) / (283.0 K) 292.76mL GAY-LUSSAC GAS LAW Relates pressure to temperature When temperature goes up, pressure goes up When temperature goes down, pressure goes down P/T=P2/T2 Practice problem: Find the final pressure of gas at 150 K, if the pressure of gas is 210 kPa at 120 K. P1= 210 kPa T1= 120 K P2= ? T2= 150 K P2= (210 kPa) (150 K) / 120 K P2= 262.5 kPa COMBINED GAS LAW Combines Boyles, Charles and Gay-Lussac’s gas laws into one equation. PV/T=P2V2/T2 Practice Problem: Oxygen occupies a fixed container of 5.5L at STP. What will happen to the pressure if the temperature rises to 300K? P2 = (5.5 L) (101.3 Kpa) (300 K) = 111.3 KPa (5.5 L) (273 K) IDEAL GAS LAW Ideal Gases DO NOT EXIST in the real world But we pretend real gases act like ideal gases so we can predict what will happen Properties Infintetly small (no volume) No attraction to other particles (No intermolecular force) Don’t condense to liquids PV=nRT P is the pressure of the gas (in atmospheres, ATM) V is the volume of the container (in liters, L) n is the number of moles of gas in the container (in moles, mol) R is Universal Gas Constant (which is 0.0820574587 L · ATM · K-1 · mol1) T is the temperature of the gas (in Kelvin) Practice: 6.2 liters of an ideal gas are contained at 3.0 atm and 37 °C. How many moles of this gas are present? n = PV / RT n = ( 3.0 atm x 6.2 L ) / ( 0.08 L atm /mol K x 310 K) n = 0.75 mol DALTON’S GAS LAW At a particular temperature, the total pressure of a mixture of two or more non-interacting (ideal) gases is equal to the sum of partial pressures of the individual gases P1+P2+P3… Practice: The pressure of a mixture of nitrogen, carbon dioxide, and oxygen is 150 kPa. What is the partial pressure of oxygen if the partial pressures of the nitrogen and carbon dioxide are 100 kPA and 24 kPa, respectively? P = Pnitrogen + Pcarbon dioxide + Poxygen 150 kPa = 100 kPa + 24 kPa + Poxygen Poxygen = 150 kPa - 100 kPa - 24 kPa Poxygen = 26 kPa GRAHAM’S GAS LAW States of Matter Parts of Solutions Solution- a homogeneous mixture (same throughout) Solute- part of solution that gets dissolved Solvent- part that surrounds the solute to make it dissolve Phase Diagram Shows what temperature and pressure combinations result in each state of matter for a particular chemical Critical point- the last pressure and temperature combination where liquids and gases exist separately Heating Curve Shows the temperature at which the state changes occur and describes how the substances uses heat Opposite phases of the heating Cooling Curve curve diagram, work backwards and they decrease Gas-condensation-liquidfreezing-solid Photos were not working, see Solubility Curve The relationship between temperature and solubility notes(class handout), know how to interpret M= m/V Molarity Calculations Molarity= moles/liters Use unit (M) Example: You make a solution using 47.9 g of HCl. The volume of the solution is 753 mL. What is the Molarity of the solution? 47.9g*1 mole/36.46g=1.31mol 753mL*1L/1000mL=.75L M= 1.31mol/.75L M=1.75M Dipole-dipole forces: the Intermolecular Forces attraction found between two polar molecules Vanderwaals forces- attraction between two nonpolar molecules Hydrogen bonding- a strong force of attraction, not considered a bond. Requires a very electronegative element (Oxygen, Nitrogen, Fluorine) bonded to a Hydrogen Cohesive forces- attracted to Intermolecular Forces other molecules of the same type Surface tension Pepper flakes float in a glass of water until a spoon is inserted into the cup and they sink Adhesive forces- molecules are attracted to other molecules of a different type Capillary action Pulls the liquid up the side of a tube creating a meniscus Specific heat calculations The specific heat is the amount of heat per unit mass required to raise the temperature by one degree Celsius • Delta, Δ or D= change of a variable. • M=Mass of the sample • Q= amount of heat that must be added. • T= temperature of the substance. • C= specific heat Formulas: c = Q/mΔt ΔQ = mcΔt Properties of Acids and Bases Acids • • • • Sour Burns/Stings Reacts with metal Electrolyte (conducts electricity) • Corrosive Examples: citric acid, vinegar Bases • • • • Bitter Slippery Non-reactive with metals Electrolyte (conducts electricity) • Corrosive Examples: ammonia, baking soda pH/OH Calculations • • • • • pH=-log[H+] [H+]=10-pH pOH=-log[OH-] [OH-]=10-pOH pH+pOH=14