charleslaw查尔斯定律演示课件.ppt

The relationship between temperature and volumeThe relationship between temperature and volume1If we place a balloon in liquid nitrogen it shrinks:How Volume Varies With Temperature So,gases shrink if cooled.Conversely,if we heat a gas it expands(as in a hot air balloon).Lets take a closer look at temperature before we try to find the exact relationship of V vs.T.2No.68F(20C)is not double 50F(10C)Yes.44 lb(20 kg)is double 22 lb(10 kg)Whats the difference?Weights(kg or lb)have a minimum value of 0.But the smallest temperature is not 0C.We saw that doubling P yields half the V.Yet,to investigate the effect of doubling temp-erature,we first have to know what that means.An experiment with a fixed volume of gas in a cylinder will reveal the relationship of V vs.T Temperature scalesIs 20C twice as hot as 10C?Is 20 kg twice as heavy as 10 kg?3Temperature vs.Volume Graph(fig.7,8 pg.430)5 10 15 20 25 30 Volume(mL)Temperature(C)0 100 273 25 mL at 22C31.6 mL,23.1 mLY=0.0847x+23.1374If a volume vs.temperature graph is plotted for gases,most lines can be interpolated so that when volume is 0 the temperature is-273 C.Naturally,gases dont really reach a 0 volume,but the spaces between molecules approach 0.At this point all molecular movement stops.273C is known as“absolute zero”(no EK)Lord Kelvin suggested that a reasonable temp-erature scale should start at a true zero value.He kept the convenient units of C,but started at absolute zero.Thus,K=C+273.62C=?K:K=C+273 =62+273=335 KNotice that kelvin is represented as K not K.The Kelvin Temperature Scale5What is the approximate temperature for absolute zero in degrees Celsius and kelvin?Calculate the missing temperatures0C=_ K100C=_ K100 K=_ C 30C=_ K300 K=_ C 403 K=_ C25C=_ K0 K=_ C Kelvin Practice273373 17324327130298 273Absolute zero is 273C or 0 K 6Looking back at the temperature vs.volume graph,notice that there is a direct relationship.It can be shown that V/T=constantRead pages 432-3.Answer these questions:1.Give Charless law in words&as an equation.Charless Law:as the temperature of a gas increases,the volume increases proportionally,provided that the pressure and amount of gas remain constant,V1/T1=V2/T2Charless Law72.A sample of gas occupies 3.5 L at 300 K.What volume will it occupy at 200 K?3.If a 1 L balloon is heated from 22C to 100C,what will its new volume be?4.Do questions 16,17,19 on page 434V1=3.5 L,T1=300K,V2=?,T2=200KUsing Charles law:V1/T1=V2/T23.5 L/300 K=V2/200 KV2=(3.5 L/300 K)x(200 K)=2.3 LV1=1 L,T1=22C=295 KV2=?,T2=100 C=373 KV1/T1=V2/T2,1 L/295 K=V2/373 KV2=(1 L/295 K)x(373 K)=1.26 LFor more lessons,visit 8