1 Properties of Matter Chapter 4 Hein and Arena Eugene Passer Chemistry Department Bronx Community College © John Wiley and Sons, Inc Version th Edition

2 Chapter Outline 4.1 Properties of SubstancesProperties of Substances 4.2 Physical ChangesPhysical Changes 4.3 Chemical ChangesChemical Changes 4.4 Conservation of MassConservation of Mass 4.5 EnergyEnergy 4.6 Heat: Quantitative MeasurementHeat: Quantitative Measurement 4.7 Energy in Chemical ChangesEnergy in Chemical Changes 4.8 Conservation of EnergyConservation of Energy

3 4.1 Properties of Substances

4 A property is a characteristic of a substance. Each substance has a set of properties that are characteristic of that substance and give it a unique identity. Properties of a Substance

5 Physical Properties

6 The inherent characteristics of a substance that are determined without changing its composition. Examples: tt aste cc olor pp hysical state mm elting point bb oiling point

7 2.4 times heavier than air color is yellowish-green odor is disagreeable melting point –101 o C boiling point –34.6 o C Physical Properties of Chlorine

8 Chemical Properties

9 Describe the ability of a substance to form new substances, either by reaction with other substances or by decomposition.

10 It will not burn in oxygen. It will support the combustion of certain other substances. It can be used as a bleaching agent. It can be used as a water disinfectant. It can combine with sodium to form sodium chloride. Chemical Properties of Chlorine

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Physical Changes

13  tearing of paper  change of ice into water  change of water into steam  heating platinum wire Changes in physical properties (such as size, shape, and density) or changes in the state of matter without an accompanying change in composition. Examples: Physical Changes No new substances are formed.

Chemical Changes

15 In a chemical change new substances are formed that have different properties and composition from the original material.

16 Heating a copper wire in a Bunsen burner causes the copper to lose its original appearance and become a black material. Formation of Copper(II) Oxide Heating a copper wire in a Bunsen burner causes the copper to lose its original appearance and become a black material. The black material is a new substance called copper(II) oxide. Copper is 100% copper by mass. Copper (II) oxide is: 79.94% copper by mass 20.1% oxygen by mass. The formation of copper(II) oxide from copper and oxygen is a chemical change. The copper (II) oxide is a new substance with properties that are different from copper.

17 Formation of Copper(II) Oxide Copper(II) oxide is made up of Cu 2+ and O Neither Cu nor O 2 contains Cu 2+ or O 2- A chemical change has occurred.

18 Water is decomposed into hydrogen and oxygen by passing electricity through it. Decomposition of Water The composition and physical appearance of hydrogen and oxygen are different from water. The hydrogen explodes with a pop upon the addition of a burning splint. The oxygen causes the flame of a burning splint to intensify. They are both colorless gases.But the burning splint is extinguished when placed into the water sample.

19 Chemical Equations

20 Water decomposes into hydrogen and oxygen when electrolyzed. reactant products yields

21 Chemical symbols can be used to express chemical reactions

22 Water decomposes into hydrogen and oxygen when electrolyzed. reactant yields 2H 2 O2H 2 O2O2 products

23 Copper plus oxygen yields copper(II) oxide. yield product reactants heat

24 Copper plus oxygen yields copper(II) oxide. yield product reactants heat 2CuO2O2 2Cu 2 O

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Conservation of Mass

27 No change is observed in the total mass of the substances involved in a chemical change.

28 sodium + sulfur  sodium sulfide 46.0 g32.1 g78.1 g 78.1 g product mass products 78.1 g reactant → mass reactants =

Energy

30 Energy is the capacity to do work

31 Types of Energy mechanical chemical electrical heat nuclear radiant

32 Potential Energy Energy that an object possesses due to its relative position.

33 increasing potential energy 50 ft 20 ft The potential energy of the ball increases with increasing height. increasing potential energy

34 Potential Energy Stored energy

35 The heat released when gasoline burns is associated with a decrease in its chemical potential energy. The new substances formed by burning have less chemical potential energy than the gasoline and oxygen. Gasoline is a source of chemical potential energy.

36 Kinetic Energy Energy matter possesses due to its motion.

37 Moving bodies possess kinetic energy. The flag waving in the wind.

38 Moving bodies possess kinetic energy. A bouncing ball. The running man.

39 The runner Moving bodies possess kinetic energy.

40 The soccer player. Moving bodies possess kinetic energy.

Heat: Quantitative Measurement

42 Heat A form of energy associated with small particles of matter. Temperature A measure of the intensity of heat, or of how hot or cold a system is.

43 Units of Heat Energy

44 The SI unit for heat energy is the joule (pronounced “jool”). Another unit is the calorie J = 1 cal (exactly) Joules = 1 calorie This amount of heat energy will raise the temperature of 1 gram of water 1 o C.

45 A form of energy associated with small particles of matter. A measure of the intensity of heat, or of how hot or cold a system is. An Example of the Difference Between Heat and Temperature

46 Twice as much heat energy is required to raise the temperature of 200 g of water 10 o C as compared to 100 g of water. 200 g water 20 o C A 100 g water 20 o C B 100 g water 30 o C 200 g water 30 o C heat beakers 4184 J 8368 J temperature rises 10 o C

47 Specific Heat

48 The specific heat of a substance is the quantity of heat required to change the temperature of 1 g of that substance by 1 o C.

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50 The units of specific heat in joules are:

51 The units of specific heat in calories are:

52 The relation of mass, specific heat, temperature change ( Δ t), and quantity of heat lost or gained is expressed by the general equation: ΔtΔt=heat mass of substance )( specific heat of substance )(

53 Example 1

54 Calculate the specific heat of a solid in J/g o C and in cal/ g o C if 1638 J raise the temperature of 125 g of the solid from 25.0 o C to 52.6 o C. (mass of substance)(specific heat of substance)Δt = heat (g)(specific heat of substance)Δt = heat heat = 1638 J mass = 125 g Δt = 52.6 o C – 25.0 o C = 27.6 o C

55 Calculate the specific heat of a solid in J/g o C and in cal/ g o C if 1638 J raise the temperature of 125 g of the solid from 25.0 o C to 52.6 o C. Convert joules to calories using cal/4.184 J

56 Example 2

57 A sample of a metal with a mass of 212 g is heated to o C and then dropped into 375 g of water at 24.0 o C. If the final temperature of the water is 34.2 o C, what is the specific heat of the metal? When the metal enters the water, it begins to cool, losing heat to the water. At the same time, the temperature of the water rises. This process continues until the temperature of the metal and the temperature of the water are equal, at which point (34.2 o C) no net flow of heat occurs.

58 A sample of a metal with a mass of 212 g is heated to o C and then dropped into 375 g of water at 24.0 o C. If the final temperature of the water is 34.2 o C, what is the specific heat of the metal? Calculate the heat gained by the water. Calculate the final temperature of the metal. Calculate the specific heat of the metal.

59 A sample of a metal with a mass of 212 g is heated to o C and then dropped into 375 g of water at o C. If the final temperature of the water is 34.2 o C, what is the specific heat of the metal? Δt = 34.2 o C – 24.0 o C = 10.2 o C temperature rise of the water Heat Gained by the Water heat gained by the water =

60 A sample of a metal with a mass of 212 g is heated to o C and then dropped into 375 g of water at o C. If the final temperature of the water is 34.2 o C, what is the specific heat of the metal? Δt = o C – 34.2 o C = 90.8 o C temperature drop of the metal Once the metal is dropped into the water, its temperature will drop until it reaches the same temperature as the water (34.2 o C). Heat Lost by the Metal heat lost by the metal heat gained by the water = =

61 A sample of a metal with a mass of 212 g is heated to o C and then dropped into 375 g of water at o C. If the final temperature of the water is 34.2 o C, what is the specific heat of the metal? specific heat of the metal = The heat lost or gained by the system is given by: (mass) (specific heat) (Δt) = energy change rearrange

Energy in Chemical Changes

63 In all chemical changes, matter either absorbs or releases energy.

64 Energy Release From Chemical Sources Type of Energy Energy Source ElectricalStorage batteries LightA lightstick. Fuel combustion. Heat and LightCombustion of fuels. Body Chemical changes occurring within body cells.

65 Chemical Changes Caused by Absorption of Energy Type of Energy Chemical Change Electrical Electroplating of metals. Decomposition of water into hydrogen and oxygen LightPhotosynthesis in green plants.

Conservation of Energy

67 An energy transformation occurs whenever a chemical change occurs. If energy is absorbed during a chemical change, the products will have more chemical potential energy than the reactants. If energy is given off in a chemical change, the products will have less chemical potential energy than the reactants.

H 2 + O 2 have higher potential energy than H 2 O energy is given offenergy is absorbed Electrolysis of WaterBurning of Hydrogen in Air higher potential energylower potential energy

69 Law of Conservation of Energy Energy can be neither created nor destroyed, though it can be transformed from one form of energy to another form of energy.

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