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Experiment: Charles’ Law Experiment

Purpose

To verify Charles’ Law- when a given mass of a gas is heated at constant pressure, the volume V of given mass of a gas is directly proportional to its absolute temperature. Theory Charles 'law, also known as Charlie - Lussac's law (Charles-Gaylussac’s Law) (Charles - Gaylussac's Law) discovered by Charles and Gaylussac respectively in 1787 and 1802 AD. Charles-Gay-Lussac's Law tells us that at conditions of constant pressure and constant amount of gas, the change of volume is proportional to the change of temperature. So

P / T = const (1) Quantitative low-density gas volume remains constant; the pressure of a gas changes by 1/273.15(= 1/273) of the pressure at 0 ° C.

)15.273

11(0 TPP (2)

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Instrument NO Accessory Qty NO Accessory Qty 1 Metal Ball 1 2 Manometer 1

3 Removable Connector 1 4 Valve 1

5 Base 1 6 Removable Bracket 1

7 Thermometer 1

Procedure 1. Set up the base and the bracket.

2. Put the metal ball in the ice bucket to lower the temperature to 0℃, and close the valve, the reading on the manometer is zero. (The reading of the manometer is relative pressure, should convert it into absolute pressure.)

3. Heat up the beaker, then wait for the temperature to rise at 0 ° C, 25 ℃, 50 ℃, 70℃, and 90 ℃, and record the pressure change.

3

6

5

2

4

1

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4. According to the equation 1 to calculate the K value of the const, obtain the error%, and plot the p-T experimental data diagram in order to verify that the constant volume of Charles- Lussac's law. Note: 1. Make sure the beaker completely immersed in water. 2. Mix the water and write down the data while the experimental system is in equilibrium. 3. Do not ceaselessly heat up the system.

Note: experimental data calculation reference:

Average const value K n

xx i

i ；Deviation xxd ii ；average standard deviation

)1(

nn

di

i

；

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Experimental Record

Charles-Gaylussac’s Law experimental data Form Room temperature=31.4℃ Room pressure= 1005.3 KPa=1.02540 2cmKgf temperature(℃) 0℃ 29.9℃ 51.1℃ 73.7℃ 90.4℃

Absolute temperature (K)

273.15 303.05 324.25 346.85 363.55

Pressure( 2cmKgf ) 1.0254 1.1454 1.2354 1.3054 1.3654

Const K value 0.376× 210 0.378× 210 0.381× 210 0.376× 210 0.376× 210

Const K value

n

xx i

i =0.377× 210

Deviation -0.186×410

-0.0699×410

0.374× 410 -0.0899×410

-0.168× 410

Average standard deviation

)1(

nn

di

i

=0.416× 410

Result x 0.377× 210 ±0.416× 410

Percentage error % 1.1%

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Charles-Gaylussac’s Law experimental data Form

Room temperature=_____℃ Room pressure= _______KPa=_______ 2cmKgf

temperature(℃)

Absolute temperature (K)

Pressure( 2cmKgf )

Const K value

Const K value

Deviation

Average standard deviation

Result x

Percentage error %

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Questions and Discussions 1. Try to describe Charles-Gaylussac’s Law based on kinetic theory. Ans.: According to kinetic theory, when temperature T rises (T is the absolute temperature K), due to the increase in the average rate of the gas molecules, the frequency of the gas molecules collision on the surface of the container increases, the collision force of the gas molecules gets greater, and the gas generates the greater pressure P. Therefore, P is

proportional to T, TP

= const, so 1

1

TP =

2

2

TP

2. Draw a diagram of the ideal gas P –T and P-1/T to verify the difference between Charles’ law and the experimental result. What is the placement when extend the line to the absolute temperature.

T(K)

P( 2cmKgf )

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3. Find errors from the linear function according to the equation (2) of Charles' law, and discuss the main factors.

Ans.: When quantitative low-density gas volume remains constant, and the temperature rises 1℃; the pressure of a gas changes by 0.0038 of the pressure at 0 ° C. The mathematical equation is )0038.01(0 TPP

From the experiment, we know that when quantitative low-density gas volume remains constant, and the temperature rises 1℃; the pressure of a gas changes by 1∕273.15 of the pressure at 0 ° C. The mathematical equation is )00366.01(0 TPP . In conclusion, because the gas collision rate of non-low-density gas is higher, the measured pressure value will be higher, the error is about 5.4% .

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