IB Investigating Specific Latent Heat of Vaporization of Water

Table 2: Mass of water evaporate over time with uncertainties

(Average of mass of water Evaporated) = (Trial 1 + 2 +3+4+5)/5

= (4.7+4.8+5.2+5.0+5.4)/5

= 4.9 g

(Uncertainty in mass of water Evaporated)         

= ((Max Value)-(Min Value))/2

= (5.4-4.7)/2

= 0.4 g

Variables on the graph

The formula given was

                                

                                Q = mL

If we divide both sides by ∆t (time)

                

                                                        

So,

                                

From the data processed above a graph of mass of water evaporated vs. time can be plotted whose slope will give

                                

Graph 2: Mass of Water Evaporated vs. Time Graph

Slope of the graph is 0.3985 g/s

Maximum Slope = 0.4110 g/s

Minimum Slope = 0.3870 g/s

So, the slope of the graph is 0.40 g/s ± 0.01 g/s

Calculating the specific latent heat of vaporization

Calculation of Uncertainty in specific latent heat of vaporization

The calculated value for latent heat of vaporization is 2500 J/g ±60 J/g

Conclusion

The graph of mass of water evaporated over time is linear because the best fit line passes through all error bars. From the calculations the specific latent heat of vaporization of water is calculated to be 2500 J/g ±60 J/g. The  of specific latent heat of vaporization of water is 2260 J/g, which is quite low. Percentage error is

        

                                           

(100)

                                                             

                                                               

The total percent error is 10.6% and the total percent uncertainty is 2.5% which is quite low compared to the percentage error. 2.5% uncertainty means the final result can be ±2.5% off. That means the total error caused by uncertainties is 2.5%, rest is from systematic errors. One of the biggest systematic errors could be the heat loss from the water to the atmosphere. A well-insulated plastic kettle was used to boil the water so there will be minimum heat loss from water to kettle and kettle to surroundings. If the heat is lost to the surroundings from water, it means that the power supplied by the kettle is not completely used to boil water as it is lost in the surrounding so the power supplied is less than 1000W.

While recording the mass of water, the mass of the water in the electronic balance was not constantly decreasing. Sometimes it increased, sometimes it decreased slowly and sometimes rapidly and because of this there was a high error in collecting data. An electronic balance with high mass capturing should have been used for better results. The electronic balance used did not have a wide base and the kettle used to boil water was overturning it which also can result in high error. An electronic balance with wide base should be used for more accurate results.

Works Cited

"Latent Heat." Wikipedia. Wikimedia Foundation, 10 May 2012. Web. 07 Oct. 2012. <http://en.wikipedia.org/wiki/Latent_heat>.