Chapter 22 Solutions

What is a solution? A solution is a mixture that has the same composition, color, density and even taste throughout The most common solutions are liquids and have water in them, but not all are To describe a solution, you might say that one substance is dissolved in another

Parts of a solution The substance being dissolved is the solute, and it is always in lower amounts that the solvent The solvent is the substance that does the dissolving and is always in higher amounts than the solute Water is known as the “Universal Solvent” because it can dissolve many things

Non liquid Solutions Solutions can be solid, like bronze, which is a mixture of both copper and tin. Brass is a mixture of copper and zinc. Solid solutions are known as alloys Air is a gaseous solution that is a mixture of Nitrogen, oxygen, carbon dioxide, hydrogen and others.

Identify the solvent and solute in each Kool Aid Water + Sugar mix Ocean water Water + Salt Bronze Copper + Tin Air Nitrogen + Oxygen, CO2 ,etc. Carbonated soft drink Water + CO2 , acidic acid, etc.

Water is Polar Water is a special molecule that can dissolve just about everything The trick is, like dissolves like Water is a polar liquid, so it can dissolve polar solids such as salt Something is considered polar if it has a positive area and a negative area in the same molecule

Polar Molecules Water Table Salt and Water

How does sugar dissolve in water Step 1: Water clusters around sugar molecules, negative ends attracted to positive Step 2: Water molecules pull sugar molecules into solution Step 3: Water and sugar molecules mix evenly, forming a solution

More Dissolving Gases can dissolve in liquids Liquids can also dissolve in liquids Making solid solutions, or alloys is more complicated, you must melt the solids down and mix them so they will remain mixed when cooled

Rate of Dissolving When one thing dissolves in another, it does so at a constant rate You can increase the dissolving rate by doing three things Stirring- brings more solvent into contact with solute Decreasing crystal size (grinding)- gives solvent more surface area to dissolve Increase temperature- makes particles move faster and mix easily

What do these three pictures represent?

Solubility and Concentration How much can dissolve? Solubility is the maximum amount of solute that can be dissolved in a solvent at a certain temperature Concentration depends on how much solute is dissolved in the solvent A solution with more solute than another in the solvent is considered more “concentrated” Example orange drink is 10 % juice, where orange juice is 100 % juice– the juice is more concentrated in one than the other

Saturated vs Unsaturated Solutions A saturated solution is one that holds all the solute that it can at a certain temperature. In an unsaturated solution, more solute can be dissolved in the solvent at a certain temperature

Solubility Curves You can use these to determine how much of a solute can dissolve in a given solvent at a certain temperature

Supersaturated Solutions Unstable solution that have more solute dissolved in the solvent than they should You can supersaturate a solution by heating it, forcing more solute to dissolve, then letting it cool As it cools, some of the solute falls out of solution You can make rock candy using a supersaturated solution of sugar and water

Solubility of Gases You can increase the amount of a gas dissolving in a liquid by INCREASING the pressure or DECREASING the temperature More carbon dioxide gas is dissolved in a cold soft drink than a warm one, that’s why sodas get “flat” as they warm up

Particles in Solution Pure water is a poor conductor of electricity. In order for water to conduct electricity well, you have to add ions to it. Solutions of ions that conduct electricity well are called electrolytes

Effects of Solute Particles Adding antifreeze to the water in your car radiator both lower the freezing point of the water AND raise the boiling point of water Meaning, that with the antifreeze, the water in your radiator won’t freeze or boil as easily Some animals such as polar fish and caribou have a natural antifreeze in their bodies that keep them from freezing in cold temperatures

When Water Won’t Work Water cannot dissolve all substances. If a substance is non-polar, meaning it has even charges all the way through and no negative and positive ends, the water cannot dissolve it Some substances are both polar and non-polar because part of the molecule is charged, and the other part is not. Ethanol is an example.

Nonpolar Solvents Goo gone, lighter fluid, dry cleaning solution are all examples of nonpolar solvents and can dissolve things that water can’t. Nonpolar solvents are often toxic and flammable They can produce harmful vapor

The Chemistry of Soap Non polar ends of soap attach to dirt and oil and dissolve it Polar ends of soap mix with water and all is washed away Soap works because it is BOTH Polar and Non-polar