### E-AIM Tutorial

 Lesson 7: Variation of Solution Properties with Temperature

### Introduction

In previous lessons, we considered thermodynamic properties such as the deliquescence, water uptake, and gas/particle partitioning of particles at a fixed temperature of 298.15 K. In Lessons 7 to 9 we examine how these properties depend on temperature.

### Preparation

Before starting, ensure that this browser window occupies only the left half of your screen. You should leave enough space for another browser window where you can enter data into E-AIM and read the results. If your screen is too small for two windows, print out this tutorial and use this window to run the E-AIM model. In these lessons we assume that you will have two browser windows open.

Select this link to open a second browser window containing the data input page for "variable temperature" calculations using Model II (http://www.aim.env.uea.ac.uk/aim/model2/mod2t.php). Arrange the windows on your screen so that both are visible and the left window contains this text.

### The Lesson

This consists of the two sets of calculations described in the links below, which should be done in the order listed.

### Conclusion

You have completed Lesson 7, and learned that:

• The water content of particles is a relatively weak function of temperature. In the two simple strong electrolyte solutions examined here the water activity coefficient in the aqueous phase and the water content of the particle both increase, by about 10% for NH4NO3 and 1.5% for (NH4)2SO4 between 275 K and 300 K.

• In a more complex solution such as aqueous H2SO4, in which there is a chemical equilibrium between the HSO4 and SO42− ions, the activity coefficient and water content changes are not as easy to predict. For the H2SO4 solutions studied here the influence of the equilibrium reaction on water uptake – via the total number of ions – appears to dominate water uptake. This results in a decrease in the water uptake by about 2% from 275 K to 300 K.

Now proceed to Lesson 8 to explore how solid/aqueous phase transitions (deliquescence) vary with temperature.