Transcript Unit 2
Unit 1 Physical Science Atoms and Elements Nature of Science "is the search for the truth“ First Nations perspectives • Medicine Wheel • Four directions • Four Elements Early Civilization perspectives • Greek Elements • Chemistry started with Democritus Classifying Matter • Matter has ‘property’ Pure Substances • Elements • Compounds Mixtures • Mechanical mixture • Suspension • Solution Using mixtures in mining Physical Properties • Water is unique Physical Properties • • • • • • • • • • • Colour and lustre Melting point Boiling point Density Solubility Ductility Crystal Shape Conductivity Hardness Texture Malleability Chemistry is the study of the composition and properties of matter Chemists interested in: 1) composition and structure of substances 2) the properties of these substances 3) the conditions under which these substances change to form new ones Forms of Matter • Mass • Volume • Four States: Solid, Liquid, Gas, Plasma Chemical Properties • Change and Reaction • Takes heat energy or light Combustion Controlled Change • Traditional uses – preserving foods • Medicines – herbs and plants Polyethylene Plastics Models of Matter Remember: began with the Greeks - Democritus Then: Alchemists Finally: Modern Chemistry Begins Models of the Atom Different Ways of Understanding 1) Greeks (Democritus) – 400 B.C. 2) Dalton – 1803 A small particle with several smaller pieces within. 3) Thompson – 1898 The Plum Pudding Model 4) Rutherford – 1911 Concentric Rings 5) Bohr – 1923 6) Scroedinger – Present Quantum Mechanical Model Based on the probability of where electrons would be found about the nucleus. Subatomic Particles We are interested in three particles and their mass, charge, and location. Mass Charge Location Proton 1 AMU + In Nucleus Neutron 1 AMU Neutral In Nucleus Electron 1/1836 AMU - Outside Nucleus AMU – Atomic Mass Unit Elements and Compounds Properties of Metals • Low melting points mean low strength • Creating alloys Properties of Non-metals • Do not conduct electricity • Could be solid, liquid, or gas Properties of Metalloids • Both metallic and non-metallic properties • Are semi-conductors of electricity Element Symbols • Short way of representing • Represents 1 atom in a chemical formula • Many based on the Latin name Some Common Elements • Iron • Carbon • Hydrogen • Oxygen • Sodium • Chlorine Compounds are a combination of two or more elements Ionic Compounds when an atom loses an electron, it becomes positive which is known as a cation. when an atom gains an electron, it becomes negative which is known as an anion. Cations and anions are attracted to each other and thus come together to form a compound. • Potassium is losing an electron and becomes positively charged. • Chloride is gaining an electron and becomes negatively charged. • K and Cl now attract each other. •The compound has a neutral charge. Molecular Compounds Are pure substances from non-metal elements. Form covalent bonds • shared electrons The two Hydrogen atoms share their outer electrons with the Oxygen atom to form H20. Chemical Formulas and Names H + H + O H2O Hydrogen (2 atoms) and oxygen (1 atom) Combine to form Water (1 molecule) In an atom/element the number of protons is always equal to the number of electrons. We always round the atomic mass to the nearest whole number. # Neutrons = Atomic Mass - Atomic Number 16 S Atomic Number – Tells us the number of protons Element Symbol Sulfur Element Name 32.06 Atomic Mass – tells us the number of neutrons and protons Ions ions are formed when an electron is either gained or lost. when an electron is gained, it becomes a negative ion and we call this an anion. when an electron is lost, it becomes a positive ion and we call this a cation. When naming a cation, simply add the word 'ion' to the end of the element name. Ex// Mg - Magnesium Mg+2 - Magnesium ion Ca - Calcium Ca+2 - Calcium ion Na - Sodium Na+1 - Sodium ion When naming an anion, drop the last few letters of the element name and add the ending -ide. Ex// O - Oxygen O-2 – Oxide N – Nitrogen N-3 - Nitride Cl - Chlorine Cl-1 – Chloride ions become charged because they want 8 electrons in their outer shell (octet) When an anion and a cation come together, they form a compound. NAMING the cation always goes first, followed by the anion. use the element name for the cation. use the ion name for the anion. 1. a) b) c) d) e) f) g) h) i) Li+1 Mg+2 Ca+2 Cu+2 Cr+3 Fe+2 Ag+1 Al+3 Fe+3 P-3 F-1 N-3 O-2 S-2 S-2 S-2 Br-1 O-2 Cl-1 K+1 Ca+2 Cr+3 O-2 N-3 KCl K2O K3N Potassium Potassium Potassium Chloride Oxide Nitride CaCl2 CaO Ca3N2 Calcium Calcium Calcium Chloride Oxide Nitride CrCl3 Cr2O3 CrN Chromium Chromium Chromium (III) (III) (III) Chloride Oxide Nitride 2. Write the chemical formula for each of the following compounds. a) b) c) d) e) f) g) h) Potassium chloride Calcium nitride Copper (II) oxide Iron (III) bromide Magnesium phosphide Aluminum selenide Chromium (III) sulfide Tin (II) oxide 3. Name each of the following compounds. a) Li2O b) Ag3N c) SnO2 d) CrCl3 e) BaS f) Fe2O3 g) Cu3P h) V2O5 G. Writing Equations Products - are the chemicals that are made or produced in a chemical reaction Reactants - are the chemicals that begin or go into the reaction before it takes place Chemical Reaction - when the chemicals that go into the reaction change and new products (chemicals) are formed. Ex. MgI2 + Na2O Reactants NaI + MgO Products When we write the compounds, we must make sure that they are balanced. ‘+’ – tells us that two compounds are combining. Key Words – combines, mixes, reacts, and, etc. ‘’ – acts as an equals sign to separate reactants and products. Key Words – to form, to produce, to make, synthesize, decompose, break down, etc. Sample Problems 1) Magnesium bromide reacts with calcium nitride to form magnesium nitride and calcium bromide. 2) Copper (II) oxide reacts with lithium phosphide and produces copper (II) phosphide and lithium oxide. 3) Tin (IV) sulfide reacts with calcium iodide and makes tin (IV) iodide and calcium sulfide. 4) Lithium chloride decomposed to form lithium and chlorine. Magic Seven – if ever the following elements are by themselves, they are found in pairs (diatomic). N2, O2, F2, Cl2, Br2, I2, At2, H2 5) Calcium reacts with iodine to form calcium iodide. 6) Chromium (III) iodide combines with sodium phosphide to make chromium (III) phosphide and sodium iodide. H. Writing Word Equations Examples 1) CaI2 + Al2O3 CaO + AlI3 2) CrI2 + 3) Fe2O3 + Cu2S CrS KF FeF3 + + CuI K2O I. Acids and Bases Acids Have a sour taste Very corrosive Neutralize bases Conduct electricity very well Dissolve in water to produce hydrogen ions (H+) in solution When an acid and a base neutralize each other, they form salt and water NaOH Sodium Hydroxide + HCl Hydrochloric Acid H2O Water + NaCl Salt Bases Have a bitter taste Very corrosive Neutralize acids Conduct electricity very well Dissolve in water to produce hydroxide ions (OH-) in solution When an acid and a base neutralize each other, they form salt and water Acid-Base Indicators • Acid – Base indicators are substances that change different colors when added to acids and bases. • Litmus Paper – red in an acid - blue in a base • Bromothymol Blue – yellow in an acid - blue in a base pH paper – is another type of indicator that can change to several different colours to tell the scientist how acidic or basic the solution is. pH Scale An acid-base indicator will not tell you how acidic or basic a solution is. The pH scale indicates the level of acidity of a solution and it ranges from 0-14. pH of 0-6.9 is acidic. pH of 7 is neutral. pH of 7.1-14 is basic. The pH scale is logarithmic (based on the power of ten). This means the difference between a pH of 5 and 6 is actually ten times. The difference between 4 and 6 is actually 100 times. Maintaining a constant pH is often very important for biological systems. Human blood has a pH range of 7.357.45. Any change from this could be fatal. Plants grow best in soil with a pH between 6 and 7. Any higher or lower, prevents the plants from absorbing nutrients. Shampoo normally has a pH of about 8. The human scalp has a pH of about 6. A scalp that becomes too basic results in dandruff. THE END Exam Time!