Physical Week 16
Day 1 | Day 2 | Day 3 | Lab | Vocabulary Test | Chemical Reactions WebQuiz

Solution Solvent Solute Concentrated Dilute Mole Saturated Unsaturated	Supersaturated Universal solvent Polar mulecule Hard water Soft water Aqueous Tincture Miscible	Solubility Freezing point depression Boiling point elevation Electrolyte Dissociation Ionization Suspension Colloid

Solution Chemistry

What happens to the freezing point of a liquid when a solute is dissolved in it?

The 2 parts of a solution: Solvent - The substance that does the dissolving. In chemistry, solvent sometimes needs to be defined as the substance present in the largest amount. Solute - The substance that is dissolved. In chemistry, solute sometimes needs to be defined as the substance present in the least amount.

Solutions may have more than one solute, but they can have only one solvent.

Solution concentration compares amounts of solute and solvent.

Concentrated solutions have a large amount of solute.
Dilute solutions have a small amount of solute.

While these two terms give you a general idea about concentration, they do not provide an exact comparison of the amounts of solute and solvent. As you learn more about solutions, you will learn to compare these amounts exactly.

Chemistry class describes solution concentration using a term called moles.

Solution saturation - compares the amount of dissolved solute in a solution with the maximum amount of dissolved solute possible under the given conditions.

	Unsaturated solutions contain less than the maximum amount possible. As more solid is added to this solution, it will dissolve.		Saturated solutions contain all the solute it is possible to dissolve under a given set of conditions. As more solid is added to this solution, it will not dissolve.
	Supersaturated solutions are unstable solutions that have been forced to dissolve more solute than should be possible under a given set of conditions. If a crystal of solid is placed into this solution, the crystal will grow. These solutions are commonly prepared by raising the temperature of the solution during dissolving, then allowing the solution to slowly cool.

Making solutions:

Water is sometimes called the universal solvent because it will dissolve so many different substances. The charges on a water molecule are not equally distributed, making it a polar molecule. The attraction for other particles increases water's dissolving ability. In the diagram at the top of this page, water molecules are shown with the red particles representing oxygen and the blue particles representing hydrogen.

Ground water with a lot of minerals dissolved in it is referred to as hard water, while soft water has few dissolved minerels. Solutions that have water as the solvent are called aqueous solutions while solutions in which alcohol is the solvent are known as tinctures.

Miscible - refers to two liquids that will dissolve in each other.

Water and alcohol are miscible.

Solubility - how much of the solute can be dissolved in a given amount of solvent.

The two main factors that affect solubility are:

• Temperature - most solvents will dissolve more solute at higher temperatures.
• Pressure - most solvents will dissolve more solute at higher pressures.
  • Effervescence - the escape of a gas from a liquid solution.

Rate of solution - refers to how quickly a solute dissolves in a solute.

The rate of solution can be increased by:

• Stirring the solution
• Grinding the solid solute
• Heating the solution

Freezing point depression - lowering the freezing point of a liquid with a solute.
Boiling point elevation - raising the boiling point of a liquid with a solute.

Homework Assignment 161:
This assignment must be turned in by the beginning of class tomorrow to receive credit.
Scoring criteria

1. Air is a gaseous solution of nitrogen and oxygen. Which is the solvent and which is the solute? Give a reason for your answer.
2. A water molecule is composed of one oxygen and two hydrogen atoms. Draw a diagram of a water molecule showing its shape. Explain why the shape makes water a "polar" molecule.
3. Carbon dioxide gas is the "carbonation" in soda pop. Write one sentence describing your experience with the solubility of CO₂ in soda pop. You must use the words "temperature", "pressure", and "effervescence" in this sentence.

Day 2

When does a solution conduct electricity?

A solution that contains ions is a good conductor of electricity.
A solution with no ions is a nonconductor.

Pure water contains no ions and is therefore a nonconductor.

Meteorologist

Electrolytes - substances that form aqueous solutions that conduct electricity. These substances produce ions in the solution. Those ions get there by one of the following processes. Although the difference between the two seems small, it is an important one. Dissociation - the separation of ions from a compound during solution. Ionization - the formation of ions from solute molecules by the action of a solvent.

1. With your table, design a safe way to verify that pure H₂O does not conduct electricity. Have your science facilitator approve your test.
2. Using your procedures in #1, determine which of the following are electrolytes.
   1. sugar
   2. table salt
   3. dish-washing soap

Day 3

Is the water in a muddy river a colloid or a suspension?

Suspensions and colloids are not like solutions.

• Suspension - a heterogeneous mixture in which the solute particles are large enough to be seen. This makes a suspension appear "cloudy".
  • The length of time the particles remain suspended in the solvent varies with particle size, but they will eventually settle out.
  • The solute particles can be removed by filtering.
• Colloid a homogeneous mixture with solute particles larger than a solution, but smaller than a suspension.
  • The solute particles are larger than atoms, ions, or molecules but are small enough to be kept permanently suspended by collisions with the solvent particles.
  • A beam of light passing through a colloid will be scattered by the solute particles.

• With your table, place about 10 ml of vegetable oil and an equal amount of vinegar in a plastic bag.
• Shake the bag and observe. Do they mix? This is a suspension.
• Add the yolk of one egg to the bag. Shake and observe. You now have a colloid.
• You might use this as a spread on a sandwich. What is it called?

Research Links:

• Solutions - Purdue University

Physical Science

The freezing point of a liquid is lowered when a solute is dissolved in it.

A solution will conducte electricity only when there are ions in the solution.

If water is taken out of a muddy river and allowed to sit undisturbed, the material in the water will settle to the bottom. This means it is a suspension.