Macroscopic Particle Level Symbolic. Structure of matter Energy that governs interactions of particles. Ways of representing behavior of matter

Transcription

1 EM 103 Macroscopic Particle Level Symbolic Lecture otes January 24, 2006 Prof. Sevian 1 Thinking like a hemist Macroscopic Matter that comprises everything Properties of materials Particle level Structure of matter Energy that governs interactions of particles Symbolic Ways of representing behavior of matter Sevian 1

2 Example: ce (solid water) Particle Level Understanding Macroscopic Understanding From hemistry & hemical Reactivity 5 th edition by Kotz / Treichel Reprinted with permission of Brooks/ole, a division of Thomson Learning: Fax Symbolic Representation 2 (s) ce crystal structure picture from What Kind of nformation? Macroscopic: iceberg has properties Appears white Floats on water Particle level: ice structure explains Regular, repeating lattice structure What are the holes? Symbolic: 2 (s) explains Basic formula: two for every one Solid phase Sevian 2

3 Macroscopic Understanding What are some properties of ice? From hemistry & hemical Reactivity 5 th edition by Kotz / Treichel Reprinted with permission of Brooks/ole, a division of Thomson Learning: Fax What kinds of properties? t melts at 32 o F t s cold (what does this mean?) t cools down a hot drink t tastes like water t has no odor t is used to put out fires t soaks into most things (wets them) Lots of materials can dissolve in it ce floats in liquid water Sevian 3

4 Macroscopic Understanding Physical properties observed and measured without changing the composition of a material (e.g., color, odor, hardness, density, melting temperature) hemical properties involve a change in composition of the material (e.g., flammability, reactivity) 7 Properties can be Extensive depend on the amount of material present (e.g., mass, volume, weight) ntensive independent of the amount of material present (e.g., density, chemical composition) Sevian 4

5 ce: What can we observe? t melts at 32 o F t s cold (it feels cold to the touch) t cools down a hot drink t tastes like water t has no odor t is used to put out fires t soaks into most things (wets them) Lots of materials can dissolve in it ce floats in liquid water 9 What kinds of properties? ce melts at 32 o F t s cold (it s cold to the touch) t cools down a hot drink t tastes like water t has no odor t is used to put out fires t soaks into most things (wets them) Lots of materials can dissolve in it ce floats in liquid water Physical, ntensive Sevian 5

6 What kinds of properties? ce melts at 32 o F t s cold (it s cold to the touch) t cools down a hot drink t tastes like water t has no odor t is used to put out fires t soaks into most things (wets them) Lots of materials can dissolve in it ce floats in liquid water Physical, ntensive 12 Why is this important? ntensive properties can be used to identify a material, extensive properties cannot ntensive properties have predictive power, extensive properties do not Physical properties depend on the organization of the particles that comprise the matter hemical properties depend on energy considerations when one kind of matter interacts with another Sevian 6

7 Think-Pair-Share A sample of ethanol ntensive or extensive? hemical or physical? Boils at 79 º Fills a volume of 200 ml Does not react with water 15 Particle Level Understanding ow does a particle level understanding explain some properties of ice? Sevian 7

8 ce Structure -- bond angles and attraction between one water s and another s give rise to regular, repeating hexagonal pattern ce is a solid up to 0º Solid structure is more expanded than liquid ce floats in liquid water Distances between some water molecules are close to the wavelength of visible light waves Snow appears white 18 Particle Level Understanding Matter is composed of atoms What is an atom? Electron cloud ucleus (protons & neutrons) From hemistry & hemical Reactivity 5 th edition by Kotz / Treichel Reprinted with permission of Brooks/ole, a division of Thomson Learning: Fax ote: ot drawn to scale! Sevian 8

9 ow many kinds of atoms? From hemistry & hemical Reactivity 5 th edition by Kotz / Treichel Reprinted with permission of Brooks/ole, a division of Thomson Learning: Fax Particle Level Understanding Matter is composed of atoms. Therefore, it can be broken down into atoms. Water ( 2 ) can be broken into hydrogen () and oxygen (), which are present in exactly a 2:1 ratio. affeine ( ) can be broken into carbon (), hydrogen (), nitrogen (), and oxygen (), which are present in exactly an 8:10:4:2 ratio. From hemistry & hemical Reactivity 5 th edition by Kotz / Treichel Reprinted with permission of Brooks/ole, a division of Thomson Learning: Fax Sevian 9

10 Symbolic Representation What information does the formula contain? xygen ydrogen 2 (s) Solid phase Two atoms ne atom 22 What hidden information does a symbol contain? Each unit (molecule) of 2 has: ne atom (red) Two atoms (yellow) Sevian 10

11 Many Symbolic Representations ores Electron loud 2 (s) Macro-Particle-Symbolic Each level provides information Macroscopic Properties of matter Particle Level nteractions between particles that give rise to matter s properties Symbolic Representation of matter Sevian 11

12 2 (s) Representation ores A two-dimensional picture of several units of water, 2, in a liquid state Electron loud A single molecule (unit) of water, 2 26 opyright Royal Society of hemistry States (Phases) of Matter From hemistry & hemical Reactivity 5 th edition by Kotz / Treichel Reprinted with permission of Brooks/ole, a division of Thomson Learning: Fax Sevian 12

13 Solid vs. Gaseous 2 2 (s) 2 (g) ote: ot drawn to scale. True density of a gas is about 1/1000 th of solid. opyright Royal Society of hemistry 28 ther ategorizations of Matter Material Pure Substance Mixture of Substances Element ompound omogeneous Mixture eterogeneous Mixture Sevian 13

14 Practice #1 Pure substance or mixture? Element or ompound? omogeneous or eterogeneous? opyright Royal Society of hemistry 30 Practice #2 Pure substance or mixture? Element or ompound? omogeneous or eterogeneous? opyright Royal Society of hemistry Sevian 14

15 Practice #3 Pure substance or mixture? Modified from opyright Royal Society of hemistry Element or ompound? omogeneous or eterogeneous? 32 Please bring your calculator to class on Thursday (and from now on) hem 103 Prof. Sevian Sevian 15