charles law查尔斯定律

1、2021/6/161The relationship between temperature and volumeThe relationship between temperature and volume2021/6/162If 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 t

2、ake a closer look at temperature before we try to find the exact relationship of V vs. T.2021/6/163No. 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 do

3、ubling 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? 2

4、021/6/164Temperature vs. Volume Graph (fig.7,8 pg.430) 5 10 15 20 25 30 Volume (mL) Temperature (C) 0 100 273 2021/6/165 If 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 v

5、olume, 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

6、, K = C + 273.62C = ? K: K=C+273 = 62 + 273 = 335 K Notice that kelvin is represented as K not K.The Kelvin Temperature Scale2021/6/166What is the approximate temperature for absolute zero in degrees Celsius and kelvin?Calculate the missing temperatures0C = _ K100C = _ K100 K = _ C 30C= _ K300 K = _

7、 C 403 K = _ C25C = _ K0 K = _ C Kelvin Practice273373 17324327130298 273Absolute zero is 273C or 0 K 2021/6/167Looking 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:Give Charless law i

8、n 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 Law2021/6/168A sample of gas occupies 3.5 L at 300 K. What volume will it occupy at 200 K?If a 1 L balloon is heated from 22C to 100C, what will its new volume be?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 =