Why Take Chemistry? 2. Career 3. How does the world work? 1.Guidance. Why doesn t a gas tank explode?

Transcription

1 Why Take Chemistry? 1.Guidance 2. Career 3. How does the world work? Ice skating Sweat Water bugs Computers Fossil fuels Atomic bombs Acid rain Fireworks Why doesn t a gas tank explode? 1

2 Chemistry What is it? Remsen s study of nitric acid Jot down your observations 2

3 Ira Remsen s Experiment Penny + nitric acid observations: 3

4 Scientific Method a logical way to study problems OBS. HYP. EXP. THEO. 1.Observation (not inference) the solution turned blue 4

5 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

6 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

7 OBS. HYP. EXP. THEO. HYPOTHESIS EXPERIMENT 7

8 OBS. HYP. EXP. THEO. 4.Theory: an explanation of why experiments give certain results. broad in scope predictive can never be proven 8

9 Theory Model What is a model? Model of the atom Remen s experiment: Cu + 4H NO 3 Cu NO 2 + 2H 2 O 9

10 Not a Bunch of Facts Patterns! 10

11 Chemistry Student definitions. Chemistry: study of the composition of substances & changes substances undergo. 11

12 Chemistry in the Real World Textiles Metallurgy Computers Engines Medicine Paper Fuels Cooking Plastics Life processes Imaging Ceramics Everything is a chemical!!! 12

13 Chemistry: Brief History B.C.: Some Greeks thought: Matter made of particles (atoms) vs. continuous Based on pure logic, rather than experimental 13

14 Middle Ages: Alchemists 14

15 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

16 Matter Anything that takes up space and has mass. MATTER? aluminum light water temperature air heat 16

17 Matter The amount of matter is measured by MASS not volume or weight. (water vs. air) 17

18 Classification of Matter Matter Mixture Substance Homo- Hetero- Com- Element geneous geneous pound (Solution) 18

19 Types of Matter 1.Substance ( pure substance ) Matter with uniform and definite composition. Every sample has exactly the same properties. example: water 19

20 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

21 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 21

22 Element vs. Compound? Classify: Water: H 2 O Vinegar: HC 2 H 3 O 2 Oxygen: O 2 Ozone: O 3 22

23 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 Homogeneous (Solution) Mixture Matter Heterogeneous Compound Substance Element 23

24 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

25 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

26 Substance, Homogeneous or Heterogeneous Mixture? gasoline beef stew gold ring 7-UP soda air sugar maple syrup wood salt cement 26

27 Mixtures can be separated by physical means chromatography (demo) distillation (next slide) magnetism (lab) filtration (lab) density 27

28 Distillation 28

29 Classification of Matter Matter Mixture physically separable Substance Homo- Hetero- Com- Element geneous (Solution) geneous pound chemically separable Kool-aid cement water oxygen 29

30 States of Matter How many? 4 states of matter! Shape Solid Liquid Gas Definite Indefinite Indefinite Volume Definite Definite Indefinite Ice Water Steam 30

31 Changing States of Matter Raise Temperature (Temp. is a measure of the average kinetic energy of the molecules that make up the substance.) 31

32 Physical Property Quality that can be observed without changing the substance s composition. Color Hardness Melting point Conductivity Solubility Density Odor Malleability 32

33 Physical Change A change that does not alter the substance s composition. Cutting Bending Change state Crushing e.g. boiling water, cutting paper 33

34 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

35 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

36 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 37

38 Elements Write the name or symbol: fluorine zinc neon chromium manganese I U Ni Ag Fe 38

39 Warm-up Define chemistry 39

40 Warm-up When water boils, it gives off air bubbles. Is this statement an observation? 40

41 Warm-up Explain the difference between a homogeneous mixture and heterogeneous mixture. Mud? Kool Aid? Milk? 41

42 Warm-up Super-fun element quiz! Argon Strontium Scandium Mercury Pb I Ne Mg 42

43 Warm-up How many states of matter are there? Which state has a constant volume and takes the shape of its container? 43

44 Warm-up Which state of matter has definite volume and takes the shape of its container? Define temperature. 44