2Scientific Method - Observe Observation – the receiving knowledge or data through the senses, or from scientific instrumentsInferences – Assumptions based on observations.Example:Observation: Car won’t start in the morning.What would you assume (or infer) the problem is?
3Scientific Method - Observe Observations:1. QualitativeDo you like this powerpoint?Usually uses the five senses.2. QuantitativeHow many words are on this powerpoint?Usually can be answered precisely.
4Scientific Method - Hypothesis Hypothesis : a statement that answers a question(a possible explanation)Tells what are the independent anddependent variables and how to measure them.
5How do Scientists Communicate? By sharing information.Poster sessionsPresentations at conferences/meetingsScientific JournalsShared Data Bases - InternetWhat happens when scientists disagree?Scientific arguments are solved throughfurther observation and experimentation
6To reveal data trends, data is placed in graphs Time (min)Temp. (˚C)1235410156207258930
7Finding Volume of Irregularly shaped items This is called Water Displacement
8The Graduated Cylinder Measures Volume Start by locating the meniscusAlways make your reading at the bottom of the meniscus!!
9Finding Density Density is a ratio between mass and volume. You need to divide to find the ratio.Density = mass divided by volumeORD = M/V
10Electronic Balance Measures Mass Turn balance onMake sure it reads “0”Place item on balanceObtain massTurn balance offSI Unit for mass is the kg
11Syllabus What is Chemistry? Chemistry is the study of matter and energy and the interactions between them.Chlorine – gas will kill youSodium – metal reacts violently with oxygenIt is stored in oil.Sodium + Chlorine= Table Salt which our bodies need
12Pure vs. Applied Science BOTTOM LINE:Pure Science is just for the knowledge.Applied Science is for someone to make money off of the invention (new technology)12
13What IS science based on? ExperimentationObservation
14Rules for significant figures: All nonzero digits are significant (1-9):1.234 g has 4 significant figures 1.2 g has 2 significant figures(2) Zeroes between nonzero digits are significant:1002 kg has 4 significant figures mL has 3 significant figures(3) Leading zeros (left) of the first nonzero digits are NOT significant; They indicate the position of the decimal point:0.001°C has only 1 significant figure0.012 g has 2 significant figures
15(4) Trailing zeroes (after a decimal point) are significant: mL has 3 significant figures, g has 2 significant figures.(5) When a number ends in zeroes that are not to the right of a decimal point, the zeroes are not necessarily significant:190 miles may be 2 or 3 significant figures50,600 calories may be 3, 4, or 5 sig figuresThe potential ambiguity in the last rule can be avoided by the use of standard exponential, or "scientific," notation.
16What is an "exact number"?Some numbers are exact because they are known with complete certainty.Most exact numbers are integers: exactly 12 inches are in a foot, there might be exactly 23 students in a class.Exact numbers are considered to have an infinite number of significant figures.
17Rules for mathematical operations In calculations, the general rule is that the accuracy of a calculated result is limited by the least accurate measurement involvedIn addition and subtraction, the result is rounded off so that it has the same number of digits as the measurement having the fewest decimal places (counting from left to right). For example,101 (3 sig figures) (5 sig figures) = ,which should be rounded to 125 (3 sig figures).= ,which should be rounded to (least shared decimal place)
182) In multiplication and division, the result should be rounded off so as to have the same number of significant figures as in the component with the least number of significant figures. For example,3.0 (2 sig figures ) × (4 sig figures) = which should be rounded to 38 (2 sig figures).
19Temperature Converting between ºC and K Example Practice ºC = K – 273 K = ºC + 273Normal human body temperature is 37 ºC. What is your temperature in K?Surgical instruments must be sterilized at 170 ºC. What is this in K?
20Physical and Chemical Changes Physical Changes: Do not alter the identity of a substanceCrushing, tearing, changes of state (solid to liquid to gas)Chemical Changes: Alter the identity or chemistry of a substanceBurning, cooking, rusting
21What is Matter?Matter is anything that has mass and volume
22States of MatterLiquidhas undefined shape but defined volume
23Pure Substances – Element Matter that can not be broken down into simpler substances under normal lab conditionsContains only one kind of atomAtom MoleculeElements (symbols) Na, Au, CWhere can you find a list of all the elements?
24Mixtures: Homogeneous Mixture with no visibly different parts.Sea water - H2O + NaClAir - N2 + O2 + CO2
25Physical and Chemical Changes Is this a physicalor a chemicalchange?Explain yourreasoning.New substances formwhen there is achemical change.
26Atomic theories J.J. Thomson 1897 Experiment - discovered electrons Atom is made up ofcharged matter
27Atomic Theories Ernest Rutherford: 1910 – Planetary Model Atom is mostly empty spaceFound the nucleus (a small dense region of positively charged particles).If the nucleus were the size of a marble,Then the atom would be the size of Cardinal’s stadiumTheorized about the neutron – not proven until 1932
28Rutherford – Gold Foil Experiment Discovered the Nucleus
29Atomic theories John Dalton – 1808 Atomic Theory: 1. Elements are made up of tiny particles calledatoms.2. Atoms of one element are identical.3. Atoms of other elements are different fromeach other.4. Atoms can combine to form compounds.5 Atoms are not created, nor destroyed, but canchange they way they are grouped together.
30Periodic Table TrendsThe most important difference between Mendeleev's table and today’s table:the modern table is organized by increasing atomic number, not increasing atomic weight.Why was the table changed?Discovery of isotopes and ions.
31Periodic Table Atomic Number = Number of Protons Hydrogen – 1 proton = #1Helium – 2 protons = #2Gold – 79 protons = #79Rules: All elements on the period table are neutral.Therefore, #of protons = #of electronsWhat about neutrons – we’re coming to that later
32Periodic Table Trends Groups – Columns Elements within a group share several common properties.Groups have the same outer electron arrangement.Like families, the share the same characteristics
33Periodic Table Trends Metals Most of the elements are metals. You see metals every day. Aluminum foil, gold, silver. If someone asks you whether an element is a metal, metalloid, or non-metal and you don't know the answer, guess that it's a metal.Properties of Metalslustrous (shiny)malleable (can be hammered)good conductors of heat and electricity
34Periodic Table Trends Group 18: Noble Gases Helium and neon are examples of noble gases.These elements are used to make lighted signs, refrigerants, and lasers.The noble gases are not reactive.He Never Argued with SupermanXenon’s a Nurse.
35Periodic Table Trends Group 17: Halogens (Examples of halogens are chlorine and iodine.)You find these elements in bleaches, disinfectants,and salts.highly reactive.
36What does this mean and why do we care? Properties of atoms correlate with the number and energy of electronsAtoms like to have full outer shellsValence electrons have the most energy(this is where all the action occurs)This will help us predict what reactions may occur when we start mixing elements together
37Main Group Elements & Their Ions Note periodicity of charges
39Periodic tableAtomic # = # of ProtonsSymbolAtomic Mass
40Periodic table Isotopes: elements with a different number of neutrons. Elements have to have the same number of protons to be the same element.
41Atomic theories Mass Number Protons Neutrons NOT Electrons (too small to wantto count)
42Periodic table Atomic mass Review: What does one proton weigh? 1 atomic mass unit (amu)What does one neutron weigh?1 amuWhat does one electron weigh?So small we will consider it to be zero
43Periodic tableAtomic # = # of ProtonsSymbolWhat isthis?
44Periodic table Why the weird number? We know that Lithium has 3 protons3 amuWe assume it has 3 neutronsWe assume the electrons are zero mass.So we total 6 amu. Where is the coming from? Isotopes6.941 is the average of all the naturally occurring isotopes of lithium.
49Periodic Table Trends Nonmetals upper right side of the periodic table (Yellow)The halogens, the noble gases, and the rest.Poor conductors of heat and electricity.Solid nonmetals are brittle and lack metallic luster.
50Hund’s Rule: electrons will not share an orbit until needed
51White Board Practice Lewis Symbols or Lewis Dot Diagrams We place the electrons on four sides of a square around the element symbol.Practice:O Na Ca BaNe H I CsCheck with your partner
52ShorthandIf it is in a row past a noble gas, we can use that for a shortcut.Short-hand Notation[Ne] 3s1[Ar] 4s2, 3d1[He] 2s2, 2p5
53Energy Notes Energy Capacity to do work or produce heat Capacity to move or change matter
54Types of Energy Potential Kinetic Stored Energy of position (water wheel, book on shelf)Chemical energy (gas, food, batteries)MotionMechanical energy (moving parts of machines)Sound: vibration of moleculesRadiant (EMR)Thermal energy (Sun’s heat)Light
55ENERGYEnergy can be converted from one form to another.Law of Conservation of Energy:energy is not created nor destroyed, but can CHANGE from one form to another.
58Wednesday – October 24Rube Goldberg Poster – Presentations
59How do atoms release energy? Energy InEnergy Out59
60Heat and Temperature Exothermic Endothermic System that releases energy into its surroundingsRelease energy because a change has occurredCombustion reactionsSystem that takes energy in as heat from the surroundingsNeeds energy from outside source in order for a change to occurChanging water to steam Or melting ice
61How do we measure energy? SI Unit: Joule (J)1 Calorie = amount of energy required to raise 1g of water by 1°C1000cal = 1 kilocalorie = 1Cal = food CaloriesConversion Factor1 calorie = Joules
62Calculating EnergySpecific Heat Capacity or Specific Heat: The amount of energy required to change the temperature of 1 g of substance by 1̊C Units are: J (Joule) g ̊C Centrigrade NOT Calories It takes different amounts of energy to heat different substances.
64Phase Change diagram Exothermic Endothermic What definition are we missing?sublimationdeposition
65Q= mCT Example 4 Practice 4 What is the specific heat of lead if a 30.0 g piece of lead undergoes a 250ºC change while absorbing calories?cal/gºC = sigfigs?3.06x10-2 cal/gºCWhat is the specific heat of an unknown substance if the addition of 950 J of heat energy caused a 20 gram sample to warm from 18ºC to 42ºC?1.97 cal/gºC = sigfigs? 2.0 cal/gºC
66Writing Formulas for Ionic Compounds Crisscross MethodExampleWrite the element symbols for the cation and anion, with the cation on the left and the anion on the right.Write each ion’s charge as a superscript.Crisscross the two charges moving them downward diagonally from one superscript to the other subscript.
67Naming Binary Ionic Compounds Name FormulaExample:Calcium ChlorideCa +2 and Cl -1CaCl2Identify the ions involvedList the cation first and then the anionDetermine that charge of each ion involvedBalance the charges so the compound is neutral.
69Naming Binary Covalent Compounds PracticeName FormulaWhat is the formula for the following compounds?Write the chemical formula of the first element listed.Write the prefix number as a subscript.Write the chemical formula of the second element listed.Pentachlorine dioxideCarbon monoxideTribromine hexasulfide
70Naming Binary Covalent Compounds PracticeFormulaNameWhat is the name of the following compounds?Write the number of the first element as a prefix, add the name of chemical.Write the number of the second element as a prefix, add the name of chemical and end in –ide.P4C8F9I6SN3
71Properties of Covalent Bonds Solids are usually softlow melting pointslow boiling pointsProperties arise because molecules are not strongly held togetherUsually found with nonmetals
72Properties of Ionic Bonds Ionic bonds are very strong (separating ions requires lots of energy)High melting points, boiling pointsCrystals are hard and brittleElectrical insulators when solid, electrical conductors when molten or dissolved in waterBetween a metal and a non-metal
73Why do atoms form bonds? Lewis Dot Diagrams Octet Rule Atoms tend to gain, lose, or share electrons in order to acquire a full set of valence electrons.Used to illustrate valence electronsUsed to illustrate how electrons rearrange during chemical reactions (when bonds are formed or broken)
74Review: Ions What are Ions? Ions are formed by adding or subtracting electrons from a neutral atom or molecule.Cation: positive charge Anion: negative charge(remove electrons) Na (add electrons) Cl-
75Naming Binary Covalent Compounds PracticeFormulaNameWhat is the name of the following compounds?Write the number of the first element as a prefix, add the name of chemical.Write the number of the second element as a prefix, add the name of chemical and end in –ide.P4C8F9I6SN3
76ORGANIC In Chemistry, Organic means it has a carbon atom in it. Question: can there be an organic ion?NO – carbon does not form ions.Can there be organic covalent bonds?YES – all carbon bonds will be covalent andtherefore they will be organic.
77Carbonated Drinks Carbonate: special group of polyatomic ion CO32- What kind of Ion doesIt need to balance?2+ like what family?Alkaline Earth MetalsHow many Carbon molecules? 1