Kinetic Energy, Heat, And Temperature

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7.3Kinetic Energy, Heat, andTemperatureKey Question: What is the relationship betweenkinetic energy and temperature of a substance?A book on a table might be sitting still, but all theparticles that make up the book never stop moving.kinetic energyenergy that all movingobjects possess; aparticle has morekinetic energy whenmoving faster andless kinetic energywhen moving slowerThis constant motion gives the particles a special kindof energy. The energy of a moving object is calledkinetic energy. All moving objects have kinetic energy.Flying airplanes, the flapping wings of a bird, andinvisible vibrating particles all possess kinetic energy(Figure 1).Figure 1 All objects that move have kinetic energy. There are even movingparticles inside a balloon.HOW PARTICLES MOVEYou know that the particles of an object are alwaysmoving. These particles have kinetic energy.Particles don’t move at the same speed. Some movevery fast. Others move very slowly. Some just vibrateback and forth. Particles can also move around andbump into one another. Some particles will have morekinetic energy than other particles.Copyright 2010 by Nelson Education Ltd.Chapter 7 Worksheet 7.3-1 139TURN

Think about bumper boats at an amusement park.There are many boats and they all move in differentways. Bumper boats will often run into each other(Figure 2). Sometimes a faster boat will hit a slowerboat. The slower boat might go faster then. Particles inan object move in a similar way.Figure 2 Bumper boats move and collide with each other randomly. The particles ofmatter do the same thing.TEMPERATUREYou know that the particles in hot and cold objects actdifferently. Most of the particles in a hot object movefaster. Most of the particles in a cold object moveslower.This tells us something about the kinetic energy of theparticles. The average kinetic energy in a hot object ishigher than the average kinetic energy in a cold object.temperaturea measure of theaverage kinetic energyof the particles of asubstance140 Chapter 7 Worksheet 7.3-1Temperature is a measure of the average kineticenergy of particles. Think about the air in a house. Itmay be warmer in one room and cooler in another.The room with the higher temperature has fastermoving air particles. The room with the lowertemperature has slower air particles.Copyright 2010 by Nelson Education Ltd.

STATES OF MATTERThere are three main states of matter:1. solid2. liquid3. gasThe particle theory can be used to explain thecharacteristics of solids, liquids, and gases (Table 1).Table 1 States of MatterState of matterDescriptionSolidThe particles in a solid vibrate cannot move around each other are packed close togetherThe shapes and volumes of solids do not change.Kinetic energy lowLiquidThe particles in a liquid move quickly vibrate, rotate, and move around each other are more spread out resist being squeezed close together will not break all the way apart from each otherLiquids take the shape of their container.Kinetic energy mediumGasThe particles in a gas move very quickly vibrate, rotate, and move past each other more thansolids or liquids have very large spaces between them are easy to compressGases expand to fill an empty container.Kinetic energy highCopyright 2010 by Nelson Education Ltd.Chapter 7 Worksheet 7.3-1 141TURN

CHANGES OF STATEThe particle theory of matter states that particles arealways moving. It also states that particles areattracted to each other. This motion (the kineticenergy) and attraction determine if the particles willform a solid, liquid, or gas.thermal energythe total kineticenergy and energy ofattraction of all theparticles of a materialThe kinetic energy of particles plus the energy ofattraction of those particles is called thermal energy.Thermal energy increases as a substance is heated.Thermal energy decreases as a substance is cooled.As thermal energy changes, the state of matter changes(Figure 3).increasing thermal energy of gcondensationliquidgasdepositiondecreasing thermal energy of particlesFigure 3 Changes in thermal energy can cause a change of state.EXPANSION AND CONTRACTIONthermal expansionan increase in thevolume of asubstance caused byheatingWhen most solids, liquids, and gases are heated, theirvolume increases. In other words, they expand, or getlarger. Thermal expansion is an increase in volumebecause of heating.Heating causes particles to speed up. This causes thekinetic energy to increase. Fast-moving particles bumpinto one another more than slow-moving particles.Thermal expansion does not change the mass of anobject. The number of particles in the object does notincrease. The volume changes because there is morespace between the particles.142 Chapter 7 Worksheet 7.3-1Copyright 2010 by Nelson Education Ltd.

Name:thermal contractiona decrease in thevolume of asubstance caused bycoolingDate:When solids, liquids, and gases are cooled, theirvolume usually goes down. In other words, they willget closer together and fill less space. Thermalcontraction is a decrease in volume because of cooling.Cooling causes particles to slow down. This causes thekinetic energy to go down. Slow-moving particlesbump into one another less than fast-moving particles.Thermal contraction will also not change the mass ofan object. The number of particles in the object doesnot decrease. The volume changes because there isless space between the particles.CHECK YOUR UNDERSTANDING1. In your own words, write a definition of “kinetic energy.”2. In your own words, write a definition of “temperature.”3. List the three states of matter in order of kinetic energy of the particles.Most kinetic energy:Less kinetic energy:Least kinetic energy:4. Think back to the Key Question. What have you learned about therelationship between kinetic energy and the temperature of an object?Copyright 2010 by Nelson Education Ltd.Chapter 7 Worksheet 7.3-1 143END

State of matter Description Solid The particles in a solid vibrate cannot move around each other are packed close together The shapes and volumes of solids do not change. . The kinetic energy of particles plus the energy o

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