Why Take “Chemistry”? 1.Guidance 2. Career 3. How does the world work? Sweat Ice skating Computers Water bugs Atomic bombs Fossil fuels Fireworks Acid rain Why doesn’t a gas tank explode? 1 Chemistry What is it? Remsen’s study of nitric acid •Jot down your observations 2 Ira Remsen’s Experiment Penny + nitric acid observations: 3 Scientific Method •a logical way to study problems OBS. HYP. EXP. THEO. 1.Observation (not inference) the solution turned blue 4 OBS. HYP. EXP. THEO. 2.Hypothesis: a proposed explanation for the observation that can be tested. The copper in the penny changed to produce the blue color. 5 OBS. HYP. EXP. THEO. 3.Experiment: a means to test the hypothesis. Try the same reaction using silver metal instead of a copper penny. 6 OBS. HYP. HYPOTHESIS EXP. THEO. EXPERIMENT 7 OBS. HYP. EXP. THEO. 4.Theory: an explanation of why experiments give certain results. broad in scope predictive can never be proven 8 Theory Model What is a model? Model of the atom Remen’s experiment: + Cu + 4H +2NO 3 Cu2+ + 2NO2 + 2H2O 9 Not a Bunch of Facts Patterns ! 10 Chemistry Student definitions. Chemistry: study of the • composition of substances & • changes substances undergo. 11 Chemistry in the Real World Textiles Metallurgy Computers Engines Medicine Paper Fuels Cooking Plastics Life processes Imaging Ceramics Everything is a chemical !!! 12 Chemistry: Brief History B.C.: Some Greeks thought: •Matter made of particles (atoms) vs. continuous •Based on pure logic, rather than experimental 13 Middle Ages: Alchemists 14 Modern Concepts 1700’s Antoine Lavoisier: • father of modern chemistry • “laboratory” • excerpt 1800’s Dalton •atomic theory based on data 1850’s Mendeleev •Periodic Table 15 Matter Anything that takes up space and has mass. MATTER? aluminum light water temperature air heat 16 Matter The amount of matter is measured by MASS not volume or weight. (water vs. air) 17 Classification of Matter Matter Mixture Homo- Heterogeneous geneous (Solution) Substance Compound Element 18 Types of Matter 1.Substance (“pure substance”) Matter with uniform and definite composition. Every sample has exactly the same properties. example: water 19 Two Types of Pure Substances Element- simplest form of matter that can exist in the lab. e.g. C, H, etc (Periodic Table) Compound- contains 2 or more different elements bonded together; it can be broken into simpler substances “chemically.” e.g. water, salt (NaCl), sugar 20 Sugar: C6H12O6 compound heat Carbon: C element + Water: H2O compound electrical energy Hydrogen: H2 element + Oxygen: O2 element 21 Element vs. Compound? Classify: Water: H2O Vinegar: HC2H3O2 Oxygen: O2 Ozone: O3 22 Types of Matter 2. Mixtures Matter Mixture Homo- Heterogeneous geneous (Solution) Substance Compound Element • two or more different substances mixed together • proportions can be varied (e.g. 20% salt in water vs. 30% salt in water) • each substance retains its original properties 23 Mixtures: Two Types 1. Homogeneous mixture mixture with uniform composition throughout mixed at the “molecular level” often transparent, not cloudy synonym is “solution.” e.g. salt water, steel 24 Mixtures: Two Types 2. Heterogeneous mixture mixture that does not have uniform composition often see small chunks or pieces of different substances often cloudy e.g. soil Italian salad dressing 25 Substance, Homogeneous or Heterogeneous Mixture ? gasoline beef stew “gold” ring 7-UP soda air sugar maple syrup wood salt cement 26 Mixtures can be separated by physical means chromatography (demo) distillation (next slide) magnetism (lab) filtration (lab) density 27 Distillation 28 Classification of Matter Matter Mixture physically Substance separable Homo- Heterogeneous geneous (Solution) ComElement pound chemically Kool-aid cement water separable oxygen 29 States of Matter How many? •4 states of matter! Shape Solid Liquid Gas Definite Indefinite Indefinite Volume Definite Definite Ice Water Indefinite Steam 30 Changing States of Matter Raise Temperature (Temp. is a measure of the average kinetic energy of the molecules that make up the substance.) 31 Physical Property Quality that can be observed without changing the substance’s composition. •Color •Solubility •Hardness •Density •Melting point •Odor •Conductivity •Malleability 32 Physical Change A change that does not alter the substance’s composition. •Cutting •Bending •Change state •Crushing e.g. boiling water, cutting paper 33 Chemical Property Ability of a substance to undergo a chemical reaction and form a new substance. Reactants products e.g. iron + sulfur iron(II) sulfide (NOT simply mixing iron + sulfur) Demo 34 Chemical or Physical ?? dry ice evaporates a car fender rusts pepper is ground-up in a pepper mill bread goes stale water freezes you file your nails you take an antacid tablet 35 Conservation of Mass & Energy In any process or reaction, both mass and energy are conserved. e.g. burn coal: where does the mass go? where does the heat energy come from? 36 37 Elements Write the name or symbol: fluorine zinc neon chromium manganese I U Ni Ag Fe 38 Warm-up Define “chemistry” 39 Warm-up When water boils, it gives off air bubbles. Is this statement an observation? 40 Warm-up Explain the difference between a homogeneous mixture and heterogeneous mixture. •Mud? •Kool Aid? •Milk? 41 Warm-up Super-fun element quiz! Argon Strontium Scandium Mercury Pb I Ne Mg 42 Warm-up How many states of matter are there? Which state has a constant volume and takes the shape of its container? 43 Warm-up Which state of matter has definite volume and takes the shape of its container? Define “temperature.” 44
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