Module 4 Intro
1. Module 4 Intro
1.17. Page 6
Module 4—Properties of Solutions
Lesson Summary
In this lesson you explored the following essential questions:
- How did Arrhenius contribute to the understanding of electrolytes, acids, and bases?
- What does it mean to dissolve a substance?
- What role does energy have in the dissolving of a solid?
Dissolving a solute might seem quite simple, but as you have learned from your work in this lesson, many events at the molecular level are involved with this process. Imagine for a moment what life would be like if dissociation and intermolecular forces did not exist. Without dissociation, a beaker of water could not dissolve ionic solids—they would simply accumulate at the bottom. Without intermolecular forces, sugars could not dissolve, and you would be deprived of an energy source required for survival.
Now that you have learned about the many chemical events required to dissolve a solid, you can appreciate how complex processes at the molecular level can result in simplicity at the macroscopic level. While billions of bonds are being broken and formed in the endothermic process of dissolving ammonium chloride in a cold pack, you get to simply squeeze the bag, shake, and apply.
Lesson Glossary
Arrhenius acid: a substance that ionizes in water to produce hydrogen ions
Arrhenius base: an ionic compound that dissociates in water to produce hydroxide ions
dissociation: the separation of ions that occurs when an ionic compound dissolves in water
endothermic: absorbing energy from the surroundings
exothermic: releasing energy to the surroundings
ionization: a process by which a neutral atom or molecule is converted to an ion; the reaction of substances in water to create ions