Properties of Matter

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Properties of Matter Chapter 4

Hein * Best * Pattison * Arena

Eugene PasserChemistry DepartmentBronx Community College

© John Wiley and Sons, Inc

Version 1.0

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Chapter Outline4.1 Properties of Substances

4.2 Physical Changes

4.3 Chemical Changes

4.4 Conservation of Mass

4.5 Energy

4.6 Heat: Quantitative Measurement

4.7 Energy in Chemical Changes

4.8 Conservation of Energy

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Properties of Substances

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• 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

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Physical Properties

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• The inherent characteristics of a substance that are determined without changing its composition.

• Examples: tastecolorphysical statemelting pointboiling point

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• 2.4 times heavier than air• color is yellowish-green• odor is disagreeable• melting point –101oC• boiling point –34.6oC

Physical Properties of Chlorine

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Chemical Properties

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

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• 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

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• 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

tearing of paperchange of ice into waterchange of water into steamheating platinum wire

• No new substances are formed.

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Chemical Changes

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

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Formation of Copper(II) OxideHeating 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.

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Formation of Copper(II) Oxide

Copper(II) oxide is made up of Cu2+

and O2-

Neither Cu nor O2 contains Cu2+ or O2-A chemical change has occurred.

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Water is decomposed into hydrogen and oxygen by passing electricity through it.

Decomposition of WaterThe 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.

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Chemical Equations

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Water decomposes into hydrogen and oxygen when electrolyzed.

reactant productsyields

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Chemical symbols can be used to express chemical reactions

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Water decomposes into hydrogen and oxygen when electrolyzed.

reactant yields

2H2O 2H2 O2

products

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Copper plus oxygen yields copper(II) oxide.

yield productreactants

heat

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Copper plus oxygen yields copper(II) oxide.

yield productreactants

heat

2Cu O2 2Cu2O

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Conservation of Mass

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

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sodium + sulfur sodium sulfide46.0 g 32.1 g 78.1 g

78.1 g productmass productsmass products

78.1 g reactant →mass reactantsmass reactants ==

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Energy

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Energy is the capacity to do work

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Types of Energy

• mechanical• chemical• electrical• heat• nuclear• radiant

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Potential Energy

Energy that an object possesses due to its relative position.

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increasing potential energy

50 ft

20 ft

The potential energy of the ball increases with increasing height.

increasing potential energy

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Potential Energy

Stored energy.

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• 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.

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Kinetic Energy

Energy matter possesses due to its motion.

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Moving bodies possess kinetic energy.

• The flag waving in the wind.

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• A bouncing ball.• The running man.

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• The runner


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• The soccer player.


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Heat: Quantitative Measurement

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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.

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Units of Heat Energy

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• The SI unit for heat energy is the joule (pronounced “jool”).

• Another unit is the calorie.

4.184 J = 1 cal

(exactly) 4.184 Joules = 1 calorie

This amount of heat energy will raise the temperature of 1 gram of water 1oC.

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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

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Twice as much heat energy is required to raise the temperature of 200 g of water 10oC as compared to 100 g of water.

200 g water

20oC

A100 g water

20oC

B100 g water

30oC

200 g water

30oC

heat beakers 4184 J 8368 Jtemperaturerises 10oC

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Specific Heat

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

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The units of specific heat in joules are:

oJoules

gram Celcius

oJ

g C

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The units of specific heat in calories are:

ocalories

gram Celcius

oJ

g C

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The relation of mass, specific heat, temperature change (Δt), and quantity of heat lost or gained is expressed by the general equation:

Δt = heatmass of substance)(specific heat

of substance)(

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Example 1

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o1638 J

125 g x 27.6 C

Calculate the specific heat of a solid in J/goC and in cal/ goC if 1638 J raise the temperature of 125 g of the solid from 25.0oC to 52.6oC.

(mass of substance)(specific heat of substance)Δt = heat

(g)(specific heat of substance)Δt = heatheatspecific heat =

g x Δt

heat = 1638 Jmass = 125 g

Δt = 52.6oC – 25.0oC = 27.6oC

specific heat = o0.475 J=

g C

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Calculate the specific heat of a solid in J/goC and in cal/ goC if 1638 J raise the temperature of 125 g of the solid from 25.0oC to 52.6oC.

o0.114 cal=

g Co0.475 J

g C

1.000 cal4.184 J

specific heat =

Convert joules to calories using 1.000 cal/4.184 J

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Example 2

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A sample of a metal with a mass of 212 g is heated to 125.0oC and then dropped into 375 g of water at 240.0oC. If the final temperature of the water is 34.2oC, 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 (34.2oC) no net flow of heat occurs.

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• Calculate the heat gained by the water.

• Calculate the final temperature of the metal.

• Calculate the specific heat of the metal.

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Δt = 34.2oC – 24.0oC = 10.2oCtemperature rise of the water

Heat Gained by the Water

o(10.2 C) = (375 )g o4.184 J

g C

heat gained by the water = 41.60 x 10 Jheat lost by the metal

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Δt = 125.0oC – 34.2oC = 90.8oCtemperature 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 (34.2oC).

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heatspecific heat = mass x Δt

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o1.60 x 10 J

(212g)(90.8 C)

o0.831 J

g C)

specific heatof the metal =

The heat lost or gained by the system is given by:

(mass) (specific heat) (Δt) = energy change

rearrange

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Energy in Chemical Changes

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

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Energy Release From Chemical Sources

Type of Energy Energy Source

Electrical Storage batteries

Light A lightstick. Fuel combustion.

Heat and Light Combustion of fuels.

Body Chemical changes occurring within body cells.

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Chemical Changes Caused byAbsorption of Energy

Type of Energy Chemical Change

ElectricalElectroplating of metals. Decomposition of water into hydrogen and oxygen

Light Photosynthesis in green plants.

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Conservation of Energy

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An energy transformation occurswhenever 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.

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H2 + O2 have higher potential energy than H2O

energy is given offenergy is absorbed

Electrolysis of Water Burning of Hydrogen in Air

higher potential energy lower potential energy

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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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Properties of Matter