Warm Up 1. Conductivity, freezing point, and boiling point are all: a. Related to volume b. Chemical properties c. Physical properties d. Related to mass 2. What property is affected when salt is spread on an icy road? How does it change? Freezing point-- becomes lower 3. When is water a good conductor? When is it a poor conductor? When it has an ionic compound dissolved in it. When it is pure.
Solutions A solution is a homogenous mixture of two or more substances. A solute is a substance whose particles are dissolved in a solution. A solvent is the substance in which the solute dissolves. Which is the solvent and the solute? solvent = water / solute=salt Dissolving salt in water
Properties of Liquid Solutions There are three physical properties of a solution that can differ from the properties of the solvent and solute: Conductivity Freezing point Boiling point
Properties of Liquid Solutions Conductivity Example: salt is a poor conductor and pure water is a poor conductor. When NaCl dissolves in water, the ions move freely and the solution conducts electricity.
Properties of Liquid Solutions Freezing point Example: The ions in road salt (MgCl 2 ) interfere with the water molecules arranging themselves into a rigid structure as it freezes. This causes the freezing point of the water to be lowered.
Properties of Liquid Solutions Boiling point Example: ethylene glycol, C 2 H 6 O 2 is used in car radiators to raise the boiling point of water. This keeps the car from overheating.
Factors Affecting Rates of Dissolving Rates of dissolving depend on the energy and frequency of collisions between solvent and solute particles Factors that affect the rate of dissolving: Surface area Stirring Temperature
Factors Affecting Rates of Dissolving Surface area When there is more surface area, there are more frequent collisions between solvent and solute particles. You can increase the surface area of a solid by dividing it into smaller particles. Which will dissolve faster? Why? Smaller particle size = more surface area
Factors Affecting Rates of Dissolving Stirring Stirring moves dissolved particles away from the surface of the solid allows for more collisions between solvent and solute particles.
Factors Affecting Rates of Dissolving Temperature Increasing the temperature of the solvent causes the particles to move faster. The number of collisions and the energy of those collisions increases.
Solubility Solubility: The maximum amount of a solute that dissolves in a given amount of solvent at a constant temperature. Usually expressed as grams of solute per 100 grams of solvent at a specified temperature. Solutions are described as saturated, unsaturated, or supersaturated depending on the amount of solute in solution.
Solubility Saturated : The solution contains as much solute as the solvent can hold at a given temperature. If you add more solute, it will not dissolve. Unsaturated : The solution has less than the maximum amount of solute that can be dissolved. If you add more solute, it will dissolve. Supersaturated : The solution contains more solute than it can normally hold at a given temperature. Supersaturated solutions are very unstable, and solute can easily be deposited out of the solution.
Factors Affecting Solubility Solubility varies with the solvent used and with the conditions of the solution: Temperature Most solids become more soluble as the temperature of the solvent increases Most gases usually become less soluble as the temperature of the solvent increases Pressure: Increasing the pressure of a solvent increases the solubility of a gas. Example: carbonated beverages
Solubility Curves Solubility of Barium nitrate Grams of solute per 100 g H 2 0 If 100 g of barium nitrate are dissolved in 100 g H 2 0 at 40°C, is the solution unsaturated, saturated, or supersaturated? unsaturated
Acids, Bases, and pH pH is the measure of the concentration of hydrogen ions (H + ) or hydronium ions (H 3 O + ) The pH scale ranges from 0 to 14. What is the pH of a neutral solution? 77 What is the pH range for acids? Less than 7 is acidic What is the pH range for bases? Greater than 7 is basic (or alkaline)
Acids, Bases, and pH Acids: Produce hydronium ions (H 3 O + ) when dissolved in water. Taste sour Change blue litmus paper to red. List three common acids: Vinegar, carbonated beverages, car batteries, gastric juices, lemon juice or other fruit and vegetable juices.
Acids, Bases, and pH Bases Produce hydroxide (OH - ) ions when dissolved in water Taste bitter Feel slippery Changes red litmus paper to blue List three common bases: Antacid, drain cleaner, baking soda, bleach, sodium hydroxide, ammonia, cleaning products
Litmus paper video 0:35 What does litmus paper tell you? Whether a solution is an acid or a base What does it not tell you? The pH What would you use to find the pH of a solution? pH Indicator paper
Worksheet Read the paragraph about solutions and conductivity to answer the questions following. You may read aloud in groups or individually. Academic expectations: Review and learn pH, acids, bases, solutions and solubility in preparation for EOC May Work alone or in groups. Turn in the completed worksheet at the end of class. Behavior expectations: Speak at volume that can only be heard at your table. Stay in your seat or ask for permission if you need to get up.
Closure: Class discussion Of the topics we reviewed today, what do you think will be the most difficult when you study it again in high school or college? Why?