Why Take Chemistry? 1.Guidance 2. Career 3. How does the world work? Ice skating Sweat Water bugs Atomic bombs Fossil fuels Fireworks Why doesn t a gas tank explode? Everything is a chemical!!! 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. EXP. THEO. HYPOTHESIS EXPERIMENT 7
OBS. HYP. EXP. THEO. 4.Theory: an explanation of why experiments give certain results. broad in scope predictive can never be proven, but scientists can have high confidence in it. 8
Theory Model What is a model? Model of the atom Remen s experiment: Cu + 4H + - +2NO 3 Cu 2+ + 2NO 2 + 2H 2 O 9
Not a Bunch of Facts Patterns! 10
Chemistry Student definitions. Chemistry: study of the composition of substances (what stuff is made of) changes substances undergo (physical and chemical changes) 11
Chemistry: Brief History B.C.: Some Greeks thought: Matter made of particles (atoms) It is not continuous. Based on pure logic, not experimental evidence. 12
Middle Ages: Alchemists 13
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 14
Matter Anything that takes up space and has mass. MATTER? aluminum light water temperature air heat 15
Matter The amount of matter is measured by MASS not volume or weight. (water vs. air) 16
Classification of Matter 17
Types of Matter 1.Substance ( pure substance ) Matter with uniform and definite composition. Every sample has exactly the same properties. example: water 18
Two Types of Pure Substances Element- simplest form of matter that can exist in the lab. Compoundcontains 2 or more different elements bonded together. C H 2 H 2 O 19
Only a compound can be broken into simpler substances. Sugar: C 6 H 12 O 6 compound heat Carbon: C element + Water: H 2 O compound electrical energy Hydrogen: H 2 element + Oxygen: O 2 element 20
Element vs. Compound? Classify: Water: H 2 O Vinegar: HC 2 H 3 O 2 Oxygen: O 2 Ozone: O 3 21
Types of Matter 2. Mixtures 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 22
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 23
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 24
Substance, Homogeneous or Heterogeneous Mixture? gasoline beef stew gold ring 7-UP soda air sugar maple syrup wood salt cement 25
Mixtures can be separated by physical means (just pull the substances apart) chromatography (demo) distillation (next slide) magnetism (lab) filtration (lab) density 26
Distillation 27
physically separable chemically separable 28
States of Matter How many? 4 states of matter! Solid Liquid Gas Shape Definite Indefinite Indefinite Volume Definite Definite Indefinite Ice Water Steam 29
Changing States of Matter Raise Temperature (Temp. is a measure of the average kinetic energy of the molecules that make up the substance.) 30
Physical Property Quality that can be observed without changing the substance s composition. (Still the same stuff!) Color Hardness Melting point Conductivity Solubility Density Odor Malleability 31
Physical Change A change that does not alter the substance s composition. (Still the same stuff!) Cutting Bending Change state Crushing e.g. boiling water, cutting paper 32
Chemical Property Ability of a substance to undergo a chemical reaction and form a new substance. (New stuff is made!) Reactants products e.g. iron + sulfur iron(ii) sulfide (NOT simply mixing iron + sulfur) Demo 33
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 34
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? 35
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Elements State the name / formula: fluorine zinc neon chromium manganese I U Ni Ag Fe 37
Warm-up Define chemistry 38
Warm-up When water boils, it gives off air bubbles. Is this statement an observation? 39
Warm-up Explain the difference between an element and a compound. Give an example of each. 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