Unit I: Matter & Energy. Textbook Chapters 1,2,11 & 12

Transcription

1 Unit I: Matter & Energy Textbook Chapters 1,2,11 & 12

2 What is Chemistry? Concerned with the properties of chemicals and the changes chemicals can undergo

3 Physical vs. Chemical Changes Physical Change change in appearance but the substance itself is not changed. Chemical Change produces new substances with different properties. Aka Chemical Reaction H 2 O + ½O 2 H 2 O 2 H 2 O (l) H 2 O (s) Paper Demo Image taken from on 8/11/11.

4 Evidence of a Chemical Change/Reaction 1. Evolution of a Gas 2. Formation of a Precipitate 3. Release or Absorption of Energy 4. Color Change in the Reaction System Image taken from on 8/11/11.

5 Properties of Matter Physical property Can be recognized without changing the substance to anything else. Examples: color, odor, density, melting pt. Chemical property Describes how a substance reacts to form a new substance. Examples: stable, reactive, flammable, inert Image taken from warningsignsdirect.co.uk on 8/11/11.

6 Common States (Phases) of Matter Solid Liquid Gas Plasma Image taken from ission_sunearth_closeup1.html on 8/11/11.

7 Solids Particles close together Particles vibrate but do not move Strong attractive forces between particles Crystalline structure (regular geometric pattern) Definite shape Definite volume Lowest PE Image taken from on 8/11/11.

8 Liquids Particles still close together. Particles vibrate and rotate allowing for movement. Weaker attractive forces between particles No regular pattern of particles Take shape of container Definite Volume Image taken from on 8/11/11.

9 Gases Particles are very far apart and move all over. Particles vibrate, rotate and translate (move from place to place). Weakest attractive forces between particles. Take shape and volume of container. Greatest disorder Highest PE Image taken from on 8/11/11.

10 Phase Changes {Change in Position of Particles (PE)} Types of Physical Change Melting Freezing (Solidification) Vaporization (Boiling) Condensation Sublimation Deposition Sublimation of Iodine Image taken from on 8/11/11.

11 Triple point At this temperature and pressure, substance can exist as a solid, liquid or gas. Under higher pressure, harder for a solid to melt or a liquid to boil. Under lower pressure, melting and boiling points lower (easier to change). Exception is water: increasing pressure, lowers freezing/melting point (think ice skating).

12 Endothermic vs. Exothermic Endothermic Heat energy is absorbed. Chemical Bonds broken in chemical rxn. 6 kcal + H 2 + I 2 2HI Exothermic Excess heat is given off (released). Chemical Bonds formed in chemical rxn. CaO(s) + H 2 O(l) Ca(OH) 2 (s) kj/mol Images taken from uline.com and en.wikipedia.org on 8/11/11.

13 Demo Is this reaction exothermic or endothermic? Ba(OH) 2. 8H 2 O + 2NH 4 NO kj/mol Ba(NO 3 ) 2 + 2NH H 2 O

14 Heating Curves Endothermic or exothermic? Be able to label all phases, phase changes, changes in temperature, PE and KE. Animated Heat Curve

15 Endothermic or exothermic? Be able to label all phases, phase changes, changes in temperature, PE and KE. Cooling Curves

16 2 Factors Affecting Phase of a Material Temperature Pressure n.f.p.= solid-liquid equilibrium point n.b.p.= liquid-gas equilibrium point Image taken from on 8/11/11.

17 Vapor Pressure Evaporation L G that takes place at the surface of the liquid and occurs at all temp s. From evaporation, vaporization & boiling, the gas (vapor) produced exerts a pressure called vapor pressure. Temp of liquid, vapor pressure Each substance has its own vapor pressure at differing temperatures. Ref Table H Vp animation Image taken from on 8/11/11.

18 Boiling Point Liquid will boil at temperature at which vapor pressure = pressure on liquid. Point of equilibrium between gas and liquid If vapor pressure = 1 atm (std pressure) then called the normal boiling point. Ref Table H Low pressure lowers b.p. demo Image taken from on 8/11/11.

19 Di = 2 Atomic = atoms 7 Diatomics 7 elements that exist in nature as paired atoms in a molecule. To identify them, go to PT start with element #7 and make the shape of a #7 N 2,O 2,F 2,Cl 2,Br 2,I 2 Missing one? Whose #1? H 2 Image taken from on 8/11/11.

20 Temperature vs. Heat Which one has more heat, a pot of boiling water or the Arctic Ocean? Describe the temperature and heat of a 4 th of July sparkler. Sparklers

21 Temperature Measure of the average kinetic energy (KE) of the particles of a substance. Instrument thermometer Units Fahrenheit ( o F) Celsius ( o C) Kelvin (K) (SI Unit) Ref Table T Δ of 1 o C= Δ of 1K Temperature Animation Animated Temp Movie Image taken from on 8/11/11.

22 Energy transferred between objects that are at different temperatures. Energy always flows from source to sink. Instrument Units calorimeter Calories Joules (SI Unit) Heat Sink (Temp) Source (Temp) Image taken from on 8/11/11.

23 Specific Heat Amount of heat energy required to raise the temperature of 1 gram of a material 1 o C What is the specific heat capacity of water? Ref Table B 4.18 J/g o C or 4.18 J/gK Equal to 1 calorie/g o C ESCI connection metals vs. water Boiling water in a paper cup Using a bomb calorimeter to determine calories of an almond (4min) Image taken from on 8/11/11.

24 3 Heat Formulas (Ref Table T) Q=mH f Q=mH v Q=mcΔT Try examples! Ref Table B Em Cee Delta Tee video Animated Heating Curve

25 Energy Conversion Energy Ability to do work or transfer heat Law of Conservation of Energy Energy can not be created nor destroyed, just converted from one form to another. 2 Types of Energy Kinetic and Potential Forms of Energy Kinetic (motion, electrical, sound, radiant, thermal) Potential (chemical, nuclear, gravitational, stored mechanical) Image taken from on 8/11/11.

26 Matter Classifying Matter Anything that has mass and volume. Should remember terms mass, weight, volume and density (Ref Table T) from esci. [Text 1-2] Image taken from on 8/11/11.

27 Elements Substances that can not be broken down into simpler substances by chemical means. Each element is composed of one type of atom. Examples: Review diatomics. allotropes Image taken from on 8/11/11.

28 Compounds 2 or more different elements chemically combined in a definite ratio Can be decomposed chemically into elements. Image taken from on 8/11/11.

29 Pure Substances A sample of matter that has definite chemical and physical properties. All samples of a single pure substance are identical in their properties. Examples: elements & compounds Image taken from on 8/11/11.

30 Mixtures 2 or more substances physically combined with no definite proportions. In a mixture, each substance retains its own properties. Homogeneous or Heterogeneous Image taken from on 8/11/11.

31 Heterogeneous Mixtures Physical combination of substances that are NOT uniform in composition throughout. Examples: sand & water, tossed salad, milk Milk under a microscope Image taken from on 8/11/11. Image taken from on 8/11/11.

32 Homogeneous Mixtures Physical combination of substances that are uniform in composition and properties throughout. Examples: salt & water, all solutions and alloys Image taken from 20Exam%20Reviews/Exam%201%20Review/salt_in_solution.jpg on 8/11/11.

33 Separating Mixtures Because mixtures are not chemically combined, they can be separated physically. Such as. Filtration Centrifugation Chromatography Magnetism Distillation Image taken from filtration.gif on 8/11/11. Image taken from on 8/11/11.

34 Fractional Distillation of Petroleum Distillation Process by which a mixture of liquids or a liquid and a solid can be separated by different boiling points. Distillation of Saltwater Image taken from on 8/11/11. Image taken from on 8/11/11.

35 Image taken from on 8/11/11.

36 Three Ways Compounds Differ from Mixtures 1. Compounds are chemically combined elements. Mixtures are physically combined substances. 2. Compounds are formed from a definite proportion. Mixtures can have varying proportions. (Compounds have a definite formula or recipe. 3. Compounds have different properties than ingredients. Mixtures retain the same properties of the ingredients. NaCl (s) NaCl (aq) Image taken from on 8/11/11.

37 Molecular Models of Matter Can you identify the following pics as element, compound or mixture??? solid, liquid or gas??? Online practice More visuals Image taken from on 8/11/11.

38 Fluids Low Density Properties of Gases Highly Compressible Completely Fill a Container Propane gas can be compressed in tanks for home heating and gas barbeques. It can be so highly compressed it becomes a liquid.

39 Pressure Pressure of Gases Amount of force exerted per unit area of surface. Measured with barometer or manometer. ex: atmospheric pressure Units of pressure Atmospheres Pascals mm of Hg Torr How a barometer works How a manometer works Demo: pressure breaking stick How Std. Atm. pressure is determined Demo: Can Crush Images taken from on 8/11/11. Evangelista Torricelli

40 STP Standard Temperature and Pressure Use Reference Table A For Gases, 273K = 0 o C 1atm = inhg = 760mmHg = 760 torr = 101.3kPa For liquids and solids, 25 o C =?K Same pressure Image taken from on 8/11/11.

41 Graham s Law of Effusion (Diffusion) Diffusion- spreading out from area of high to low density. Effusion-movement of gas through a small opening into an evacuated chamber. The rate of diffusion of a gas is inversely proportional to the square root of the gas s density. Video Image taken from on 8/11/11.

42 Kinetic Theory of Gases or Kinetic Molecular Theory (KMT) 1. Gas-composed of individual particles which are in continuous, random straight line motion 2. Not all particles have same KE, avg KE of particles=temp of gas 3. Elastic collisions between particles transfer of energy w/ no loss(total energy stays the same.) 4. Volume of gas particles ignored compared to volume of space in which they contain. 5. Gas particles no attraction to each other Image taken from ek6/gas_pressure.gif on 8/11/11.

43 Gases that follow the 5 points of KMT. Best examples are gases with small molecular masses like H 2 and He. Ideal Gases Low pressure and high temperature conditions are the best for ideal gases. Image taken from on 8/11/11.

44 Real Gases deviate from KMT. Especially under High pressure and Low temperatures. Can you think of ways gases would deviate (not follow) from KMT? KMT Image taken from on 8/11/11.

45 Gas Laws Boyle s Charles Gay-Lussac Combined Ideal

46 Boyles Law At constant temp., volume of a given mass of gas varies inversely with pressure PV=K or V 1 /V 2 = P 2 /P 1 Example: Robert Boyle ( ) Image taken from on 8/11/11. Animation Animation 2 w/ graphing

47 Charles Law At constant pressure, the volume of a given mass of gas varies directly with Kelvin temperature. V 1 /V 2 =T 1 /T 2 or V/T=k Example: Jacques Charles ( ) Image taken from m?id=what-is-charles-lawon 8/11/11. V Animation Balloon Demo

48 Gay-Lussac At constant volume, the Kelvin temperature of a gas is directly related to the pressure. P 1 /T 1 = P 2 /T 2 Example: Joseph Gay-Lussac ( ) Image taken from on 8/11/11. Pressure Cooker Animation Image taken from toolskitchen.net on 8/11/11.

49 Combined Gas Law Changes in volume, pressure and temperature of a gas often occur simultaneously. Combine Boyle s, Charles & Gay-Lussac s. Formula on Ref Table T, remember K temp. Example: Narrated Animation of all Gas Laws

50 Examples a) A sample of ml of oxygen gas is under mmhg of pressure. What will be the new volume of O 2 (g) if the pressure is reduced to mmhg? b) A ml Helium balloon is at a temperature of o C. What is the size of the balloon going to be if the system is warmed to 7.00 o C? c) A 175mL sample of gas is at 20.0 o C and 1.00 atm. What will the new volume be if the temperature is lowered to 10.0 o C and the pressure is raised to 1.50 atm?

51 Partial Pressures Pressure exerted by each of the gases in a gas mixture. Total P = sum of partial pressures solve? John Dalton ( ) Image taken from on 8/11/11. Image taken from ges/chfa_02_img0256.jpg on 8/11/11. Image taken from on 8/11/11.

52 Avogadro s Hypothesis Equal volumes of gases under the same conditions of temp. & pressure contain equal numbers of particles. Avogadro s #=1 mole=6.02 X10 23 Amedeo Avogadro ( ) Image taken from o_avogadro on 8/11/11. Image taken from on 8/11/11.

53 Ideal Gas Law Includes the number of moles of gas related to P (atm. or kpa), T (K) &V (L). Derived from KMT. PV=nRT Which variables are directly related? Inversely related? Example: a) At 5.00 atmospheres pressure and 70.0 o C, how many moles are present in 1.50 liters of O 2 gas? n= number of moles of gas R is the gas constant R= L. atm/mol. K R=8.314 L. kpa/mol. K b) How many moles of gas are contained in liters at kpa and 0.00 o C?