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CHAPTER 14, 16 & 18 WHAT IS CHEMISTRY? Balloon Demonstration (Conceptual Integrated Science Explorations: p.259) Hypothesis – what will happen when you fill the balloon with the fragrance? 1. Get balloon & smell it – record 2. Fill balloon with fragrance & then fill with air– smell & record 3. Answer questions 1 & 2 under Analyze & conclude on pg 259 Questions Open your BOOK to page 273 and answer questions: 3-7 Bill Nye the Science Guy! ATOMS http://www.youtube.com/watch?v=Ez0Poi1 YJS0&feature=endscreen&NR=1 (Full video - 22:11) http://www.youtube.com/watch?v=cnXV7P h3WPk (video clip - 6:37) Chapter 14: The Atom 14.1 & 14.2: The Atom Submicroscopic (smaller than microscope level!) particles. Teeny-tiny basic units that make up stuff 1 grain of sand contains around 125 MILLION TRILLION atoms. The # of atoms in a baseball is equivalent to the # of ping-pong balls that could fit inside Earth There are more than 100 different kinds & are listed on the periodic table Parts of an Atom Atoms are made up of EVEN SMALLER particles Subatomic particles: – Protons (positive charge) – Neutrons (no charge) – Electrons (negative charge) The Atom Atomic Nucleus & Electrons Atomic Nucleus - core of atom, makes up most of atom’s mass, consists of PROTONS & NEUTRONS. ELECTRONS buzz around the empty space surrounding the nucleus. Negative charge 14.3: Protons & Neutrons PROTON– heavy particle in the nucleus that’s positively (electric) charged. Has SAME quantity but OPPOSITE charge of electron NEUTRON – same mass as proton, but no charge, also found in the nucleus. Nucleons - general term for subatomic particles in the nucleus: protons & neutrons Atomic Number = to the number of PROTONS in atomic nucleus Order of elements Ex: – Hydrogen (H) has 1 proton per atom, the atomic number – Helium (He) has 2 protons in nucleus & atomic number is 2 Which element does the diagram represent? Nitrogen! Which atom does this diagram represent? OXYGEN! Periodic Table of Elements pages 264-266 & 16.6 ELEMENTS Any material made of only one type of atom Elements are the building blocks of matter There are 115 known elements today, 90 which occur naturally All elements are listed in a chart called the PERIODIC TABLE ELEMENTS (Cont) Each element has a unique symbol – The first letter is always capitalized, the second letter is always lower case Fluorine is F, not f Cobalt is Co, not CO (which is carbon monoxide) Oxygen is O The smallest unit of an element is the atom Atomic Symbol Each element has a unique symbol – The first letter is always capitalized, the second letter is always lower case Fluorine is F, not f Cobalt is Co, not CO (which is carbon monoxide) Oxygen is O Groups Vertical column of table Also called a family All elements in the same Group have similar properties Ex: Noble Gases He, Ne, & Ar are all gases Groups cont’d Group Names Group 1: Alkali Metals Group 2: Alkaline-earth Metals Group 3 – 12: Transition Metals Group 13 – 15: No Common Name Group 16: Chalcogens Group 17: Halogens Group 18: Noble Gases Periods Horizontal row Across any period (horizontal row) the properties of elements gradually change – called a periodic trend Trends repeat from one row to the next Periods Ex: Atom Size - atoms get smaller as you move from left to right BIGGER to smaller 14.4: Mass Number Mass Number: the total number of protons and neutrons (total number of nucleons) Hydrogen-1 Hydrogen-2 Hydrogen-3 14.4: Isotopes Isotopes: any member of a set of atoms of the same element whose nuclei contain the same number of protons but different numbers of neutrons mass number – atomic # = # of neutrons Ex: Iron-56 55 2 6 Fe Isotope Examples Iron-56 & Iron-55 How many neutrons are in each? (Hint: See PT) Iron-56: 56 – 26 = 30 neutrons Iron-55: 55 – 26 = 29 neutrons 7 3 Li isotope How many neutrons are in lithium? 7 – 3 = 4 neutrons If an atom has 6 electrons, 8 neutrons, and 6 protons, what is the mass number? What is the element? mass number = 14, the element is Carbon Isotopes Use a Periodic Table to complete the following table Isotope Mass Number Isotope Notation Protons Electrons Neutrons Hydrogen-1 Chlorine-? 19 Nitrogen-14 Potassium-40 Arsenic-? Gold-197 42 Isotopes Answers Isotope Hydrogen-1 Chlorine-36 Nitrogen-14 Potassium-40 Arsenic-75 Gold-197 Mass Number 1 36 14 40 75 197 Isotope Notation 1H 1 36 Cl 17 14 N 7 40 K 1 9 75 33 As 197 79 Au Protons Electrons Neutrons 1 1 0 17 17 19 7 7 7 19 19 21 33 33 42 79 79 118 Isotopes Use a Periodic Table to complete the following table Isotope Mass # Isotope Atomic # Notation Protons Electrons Neutrons Oxygen-16 Calcium-40 48 36 Copper-64 34 15 45 15 Isotopes Answers Isotope Oxygen-16 Calcium-40 Krypton-84 Copper-64 Selenium-79 Phosphorus-30 Mass # 16 40 84 64 79 30 Isotope Atomic Protons Notation # 16O 8 40 Ca 20 84 36Kr 64 2 9 Cu 79 34 Se 30 15 P Electrons Neutrons 8 8 8 8 20 20 20 20 36 36 36 48 29 29 29 35 34 34 34 45 15 15 15 15 Atomic Mass Atomic Mass: The sum of the masses of all the atom’s electrons, protons and neutrons 14.5: Electron Shells Within the atom, electrons behave as though they are arranged in shells. Each shell can hold a certain number of electrons – Innermost shell: 2 – Shells 2-3: 8 each – Shells 4-5: 18 each – Shells 6-7: 32 each Bohr’s Shell Model Make a shell model for the following atoms: –Fluorine –Neon –Chlorine –Argon –Iron –Arsenic Valence Electrons Electron in outermost shell of an atom Atoms combine to form molecules by valence electrons “combining power” of an atom Chapter 16: Elements of Chemistry 16.1: Chemistry: The Central Science Chemistry is the study of matter and the transformations it can undergo. What is matter? – Anything that has mass and takes up space. IMPORTANCE OF CHEMISTRY Chemistry is all around you. – Air you breathe – Food you digest – Clothes you wear – Textbook you read Chemistry is often said to be the central science. Syringe Activity 1. 2. 3. 4. Materials: Syringe, cup of water, mini marshmallow, (rubber stopper) Do the following & Record observations Double the pressure Quadruple the pressure Reduce volume in half – let go of plunger Start @ 0mL, block end & try to lift plunger all the way out Indicates atmospheric pressure Add marshmallow. Pressurize it as much as possible. 6. Start with plunger close to marshmallow. Cover end and try to lift plunger. 7. Remove marshmallow. Completely fill syringe with water. Compress syringe Why was it hard to quadruple pressure? What was happening to the air particles inside as you tried to add pressure? Why was it so hard to lift the plunger out of the syringe? Why did the marshmallow respond as it did to the changes in pressure? Why can’t you compress water? 5. 16.2: The Submicroscopic World Submicroscopic – beyond the microscopic level. Atoms & molecules Molecules - some atoms link together to form larger but still incredibly small units of matter called molecules Phases of Matter Liquid – matter that has a definite volume but no definite shape, assumes shape of container Solid – matter that has definite shape & volume Gas – matter that has neither definite volume nor definite shape, fills any space available PHASES OF MATTER Complete the following chart: SOLID LIQUID SHAPE VOLUME Arrangement of Particles Interaction between Particles Movement of Particles Example Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings GAS PHASES OF MATTER Complete the following chart: SOLID LIQUID GAS SHAPE Definite shape Shape of container Shape of container VOLUME Definite volume Definite volume Volume of container Arrangement of Particles Fixed, very close Random, close Random, far apart Interaction between Particles Very strong Strong Essentially none Movement of Particles Very slow Moderate Very fast Example Ice, salt, iron Copyright © 2005 by Pearson Education, Inc. Publishing as Benjamin Cummings Water, oil, vinegar Water vapor, helium, air WATER AND ITS STATES OF MATTER 16.3: Changes of Phase In order to change the phase of a substance, you must either add heat or remove heat Change of Phase Melting: Solid to liquid Boiling: Liquid to gas (beneath the surface) Evaporation: Liquid to gas (surface) Boiling & Evaporation Melting – The above 3 require input of heat energy Condensation Condensation: Gas to liquid Freezing: Liquid to solid – The above 2 release heat energy Freezing Change of Phase Diagram 16.4: Physical & Chemical Properties & Changes PHYSICAL PROPERTIES Any physical attribute of a substance such as color, density, texture, hardness, & phase Each substance has unique physical properties Examples – Sulfur appears as a yellow powder – The boiling point of water is 100 oC – Carbon monoxide is odorless PHYSICAL CHANGES Change in substance’s physical property but doesn’t change the composition – Examples include: Any change in the state of matter (e.g. freezing or boiling water) Sawing wood Crushing a tablet Bending a wire Dissolving salt in water CHEMICAL PROPERTIES Describe ways pure substances behave when interacting with other pure substances. Examples – Iron reacts with oxygen to form rust. – Platinum does not react with oxygen at room temperature. CHEMICAL CHANGES Changes the identity of the substance as the chemical composition changes. – Also called chemical reactions Examples: – Tarnishing of silver (Ag forms AgS) – Rusting of iron (Fe forms Fe2O3) 16.5: Determining Physical & Chemical Changes Molecules: Physical Chemical Change in New physical material or appearance? same after returning to original conditions? New Examples: material that has its own unique set of physical properties? 16.5: Determining Physical & Chemical Changes Molecules: Physical Chemical Molecules are the same as started with Original molecules have been destroyed & new ones are in place Change in New or physical same appearance? material after returning to original conditions? yes yes same new New Examples: material that has its own unique set of physical properties? no yes •Ice melting •Potassium chromate •Iron turning to rust •Ammonium dichromate CHEMICAL REACTIONS Are the same as a chemical change Are expressed using chemical equations. Rusting of iron: 4 Fe + 3 O2 2 Fe2O3 (rust) reactants products Meaning: Four atoms of iron react with three molecules of oxygen to form two molecules of rust The Law of Conservation of Matter/Mass Matter can neither be created nor destroyed in an isolated system Brain Pop: Chem equations & Conservation of Matter/Mass CHEMICAL REACTIONS (Cont) Zn + 2 HCl Zinc hydrochloric acid ZnCl2 + H2 zinc chloride hydrogen gas Meaning: One atom of zinc reacts with two molecules of hydrochloric acid to produce one molecule of zinc chloride and one molecule of hydrogen gas. How to Balance Chemical Equations 1. Write the unbalanced equation. Chemical formulas of reactants are listed on the left-hand side Products are listed on the right-hand side Reactants and products are separated by putting an arrow between them to show the direction of the reaction. 2. Balance the equation. Apply the Law of Conservation of Mass to get the same number of atoms of every element on each side of the equation. Start by balancing an element that appears in only one reactant and product. Once one element is balanced, proceed to balance another, and another, until all elements are balanced. Balance chemical formulas by placing COEFFICENTS in front of them. DO NOT add subscripts, because this will change the formulas. Practice Balancing Equations 1 __Fe + __Cl2 __FeCl3 2 __Al + __O2 __Al2O3 3 __CH4 + __ O2 __ CO2 + __ H2O 4 __ Na + __ Cl2 ___ NaCl 5 __ N2 + __ H2 ➜ ___ NH3 6 __ Al + __ HCl ➜ __ AlCl3 + ___ H2 Practice Balancing Equations: ANSWERS _2_Fe + _3_Cl2 _2_FeCl3 _4_Al + _3_O2 _2_Al2O3 Balancing Chemical Equations Modeling Clay Activity Use modeling clay to represent each element to balance the chemical equations on the chart. Example: – Fe + Cl2 FeCl3 Fe (iron) = YELLOW clay Cl (chlorine) = BLUE clay Balancing Chemical Equations Modeling Clay Activity Use modeling clay to represent each element to balance the chemical equations on the chart on the next slide. Example: – Fe + Cl2 FeCl3 Fe (iron) = YELLOW clay Cl (chlorine) = BLUE clay Balancing Chemical Equations Modeling Clay Activity Make the equations on your desk H 2 + O 2 H2O H2O2 H2O + O2 Na + O2 Na2O N2 + H2 NH3 P4 + O2 P4O10 Fe + H2O Fe3O4 + H2 C + H2 CH4 Na2SO4 + CaCl2 CaSO4 + NaCl C2H6 + O2 CO2 + H2O Al2O3 Al + O2 Reactants (Start) Products (Start) Balanced Equation Reactants (Final) Products (Final) CLASSIFICATION OF MATTER ELEMENTS (you have these notes already) Any material made of only one type of atom Elements are the building blocks of matter There are 115 known elements today, 90 which occur naturally The periodic table displays the elements ELEMENTS (Cont) (you have these notes already) Each element has a unique symbol – The first letter is always capitalized, the second letter is always lower case Fluorine is F, not f Cobalt is Co, not CO (which is carbon monoxide) Oxygen is O The smallest unit of an element is the atom COMPOUNDS Atoms of different elements bond to one another to make a compound – NaCl (table salt) Contains sodium (Na) and chlorine (Cl) NaCl is the chemical formula – H2O (water) Contains 2 atoms of hydrogen (H) and 1 atom of oxygen (O) H2O is the chemical formula Elements in compounds are combined in a definite ratio – H2O is water but H2O2 is hydrogen peroxide COMPOUNDS (cont) Are H2 and O3 considered elements or compounds? Why? Heterogeneous Mixture The different components can be seen as individual substances Different parts are visible Ex: Pulp in orange juice, sand in water, oil & water, pizza Homogeneous Mixture Have same composition throughout Can’t see separate parts Ex: Air, blood, fog, salt water CLASSIFICATION OF MATTER Classify the following as an element, compound, homogeneous mixture, or heterogeneous mixture. a. b. c. d. e. f. Fog Gasoline Helium Sulfuric acid (H2SO4) Orange juice from squeezed oranges H2 PRACTICE PROBLEM Identify the following properties and changes as physical or chemical. a. The copper sheets that form the “skin” of the Statue of Liberty have acquired a greenish coating over the years. b. Carbon appears as black powder. c. Adding food coloring to water. d. Wood burns in air.