MATERIALS

AND EQUIPMENT

125 mL Erlenmeyer flask, one-hole rubber stopper, glass and rubber tubing, pneumatic trough, thermometer, screw clamp.

DISCUSSION

The quantitative relationship between the volume and the absolute temperature of a gas is summartzed in Charles'law. This law states: at constant pressure, the volume of a particular sample of gas is directly proportional to the absolute temperature. Charles' law may be expressed mathematically: V ". T (constant pressure) V = kT o, : T = k (constant pressure) (1) (2)

where V is volume, T is Kelvin temperature, and k is a proportionality constant. dependent on the number of moles and the pressure of the gas. If the volume of the same sample of gas is measured at two temperatures, V1/T1 = k and V2/T2- k, and we may say that V, V, or V" = (V,f[]) z \ T1 T2 "[Tr/ {.o.rrt.nt pressure)

(3)

where V1 and T, represent one set of conditions and V2 and T2 a different set of conditions, with pressure the same at both conditions. Experimental Verification of Charles' Law

This experiment measures the volume of an air sample at two temperatures, a high temperature, Ts, and a low temperature, T1. The volume of the air sample at the high temperature, (Vn),decreases when the sample is cooled to the low temperature and becomesV1. All of these measurements are made directly. The experimental data is then used to verify Charles'law by two methods: 1. The experimental volume (V""o) measured at the low temperature is compared to the V1 predicted by Charles' law where

Yy(t oretic (vH,[ he at)= + )

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2. The V/T ratios for the air sample measured at both the high and the low temperatures are compared. Charles'law predicts that these ratios will be equal.

V"_V"

TH TL

Pressure Considerations The relationship between temperature and volume defined by Charles' law is valid only if the pressure is the same when the volume is measured at each temperature. That is not the...

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