# 7-2: Concentration & Solubility Science Standard 8.5.a: Students know physical processes including freezing and boiling, in which a material changes form.

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7-2: Concentration & Solubility Science Standard 8.5.a: Students know physical processes including freezing and boiling, in which a material changes form with no chemical reaction.

California Standards Science Standard 8.5.a: Students know physical processes including freezing and boiling, in which a material changes form with no chemical reaction.

Input See vocab sheet

Input & Modeling Concentration To measure concentration, you compare the amount of solute to the total amount of solution. A concentrated solution has a lot of solute dissolved in a certain amount of solvent. You can make it more concentrated by adding solute or taking away solvent A dilute solution has only a little solute dissolved in a certain amount of solvent. So to dilute a solution you add more solvent Concentration can be measured as the percent of solute in solution by volume or mass.

Input & Modeling To calculate the concentration of a solution, compare the amount of solute to the amount of solution and multiply by 100 percent. For example, if a solution contains 10 grams of solute dissolved in 100 grams of solution, then its concentration can be reported as 10 percent.

Input & Modeling Practice Problem A solution contains 15 ounces of solute dissolved in 60 ounces of solution. What is the concentration of the solution? 15/60 = 0.25 25%

Input & Modeling Solubility characteristic  You can identify a substance by its solubility because it is a characteristic property of matter.  Solubility is a measure of how much solute can dissolve in a solvent at a given temperature. If you can continue to dissolve more solute, you still have an unsaturated solution. If no more solute will dissolve, you have a saturated solution.

Input & Modeling Factors Affecting Solubility pressure, the type of solvent, and temperature. Factors that affect the solubility of a substance include pressure, the type of solvent, and temperature. An increase in pressure increases the solubility of gases. Ionic and polar compounds usually dissolve in polar solvents – “like dissolves like” solids The solubility of most solids increases as temperature increases. Gases Gases become less soluble in a liquid when the temperature of the liquid goes up.

Input & Modeling Factors Affecting Solubility Pressure Pressure Shaken bottle of soda “like dissolves like” “like dissolves like” Soap and water cleaned with water based paints Oil paints cleaned with turpentine Temperature Temperature Solid Rock/crystal candy (have to heat water up to add more sugar in it and then cool to get sweet candy) Gas Warm soda going flat faster (Carbon dioxide escapes faster)

Input & Modeling The solubility of the compound potassium nitrate (KNO 3 ) varies in water at different temperatures.

Input & Modeling KNO 3 is least soluble at 0ºC. Reading Graphs: At which temperature shown in the graph is KNO 3 least soluble in water?

Input & Modeling Approximately 65 g of KNO 3 are needed to saturate a water solution at 40ºC. Reading Graphs: Approximately what mass of KNO 3 is needed to saturate a water solution at 40ºC?

7-3: Describing Acids & Bases What are the properties of acids and bases? Science Standard 8.5.e: Students know how to determine whether a solution is acidic, basic, or neutral.

What do these two things have in common? They both have a sour taste because they contain acids.

Input See vocab sheet

Input & Modeling Properties of Acids & Bases An acid tastes sour, reacts with metals and carbonates, and turns blue litmus paper red. PROPERTIES: Sour Taste Scientist do not use this one to test- too dangerous Reaction with metals hydrogen gas Acids react with some metals (magnesium, zinc, iron) to produce hydrogen gas corrosive Acids are corrosive

Input & Modeling Properties of Acids & Bases PROPERTIES: Reaction with carbonates When mixed with acid it will produce carbon dioxide (gas) Geologist use this to identify limestone (since it contains carbonates) Reactions with indicators Litmus paper is an example

Input & Modeling Properties of Acids & Bases A base tastes bitter, feels slippery, and turns red litmus paper blue. COMMON Bases= calcium and sodium hydroxide, and ammonia Properties Bitter taste Slippery feel – Be careful touching bases- they can burn your skin Reaction with indicators – Bases turn Blue

Input & Modeling REMEMBER…

Input & Modeling Uses of Acids & Bases Acids and bases have many uses around the home and in industry. You can find acids and bases everywhere! Vitamins (A) Fertilizers(A) Car batteries (A) Cleaning products (B) Baking soda (B) Baking soda reacts with acid (such as buttermilk) and creates gases to make things light and fluffy Mixing cement (B)

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