1. Understanding Solutions
7-1

2. What is a Solution? Solution Solvent Solute
Well-mixed mixture that contains a solvent and at least one solute
Solvent
Part of a solution present in the largest amount
Solute
Substance that is present in a solution in a smaller amount and is dissolved by the solvent
Water is the universal solvent; because it dissolves so many substances.

4. Colloids
Mixture containing small, undissolved particles that do not settle
A colloid contains larger particles than a solution
The particles are too small to be easily seen, but large enough to scatter a light beam

6. Suspensions
Mixture in which particles can be seen and easily separated by settling or filtration
Suspensions do not have the same properties throughout
Contains visible particles that are larger than those in solutions or colloids

8. Particles in Solution
When a solution forms, particles of the solute leave each other and become surrounded by particles of the solvent
Ionic and molecular solutes
Ionic solutes break into ions when they dissolve
Molecular solutes break into individual neutral molecules
Solutes and Conductivity
Solution of ionic compounds conducts electricity
Solution of molecular compounds doesn’t conduct electricity

9. Effects of Solutes on Solvents
Solutes lower the freezing point and raise the boiling point of a solvent
What are examples of how we use this property?
We put salt on roads to prevent ice from forming or to melt it
We add salt to water when making pasta, increases the boiling temperature so water is hotter when pastas is cooked

10. Concentration and Solubility
7-2

11. Concentration Dilute solution Concentrated solution
A mixture that has only a little solute dissolved in it
Concentrated solution
A mixture that has a lot of solute dissolved in it
You can change the concentration of a solution by adding more solute
You can add more water to make a more diluted solution

13. Measuring Concentration
To measure concentration, you compare the amount of a solute to the amount of solvent or to the total amount of the solution
Measurement is in grams

14. Sample Problem
Rubbing alcohol sold in grocery stores is a mixture of isopropyl alcohol and water. The concentration of a 473.0mL is 70% alcohol by volume. Find the volume of alcohol in the solution.
0.7 x 473.0mL = mL

15. Practice problem #1
What is the concentration of a solution that contains 45 grams of sugar in 500 grams of solution?

16. Practice Problem #2
How much sugar is dissolved in 500 grams of a solution if the solution is 70 percent sugar by mass?

17. Solubility
Definition: the measurement of how will a solute can dissolve in a solvent at a given temperature
Saturated and Unsaturated solutions
Saturated: contains as much solute as possible at a given temperature
Unsaturated: the solution does not hold as much solute as is possible at the given temperature

20. Working with Solubility
Solubility tells you how much solute you can add before a solution becomes saturated
Solubility is a characteristic property of a compound
It helps you identify a compound

21. Changing Solubility Solublities can change depending on conditions
Temperature
In solids increasing temperature, increases solubility
When heated a solute can hold more solute than it can hold at cooler temperatures
Supersaturated solution- a mixture that has more dissolved solute than is predicted by its solubility at the given temperature
Gases-become less soluble when the temperature goes up

22. Pressure
The higher the pressure, the more gas can dissolve

23. Which person’s tea will dissolve the sugar faster?

24. Solvents Ionic and polar covalent compounds usually dissolve
Polar and non-polar compounds do not mix very well

26. Describing Acids & Bases
7-3

27. Properties of Acids
Acids- a substance that tastes sour, reacts with metals and carbonates, and turns blue litmus paper red
Sour taste
Fruits, tea, spoiled milk
Some acids are hard to identify, or may not be safe to eat
Not a good way to identify if a solution is an acid

28. Reactions with carbonates Reactions with indicators
Reactions with metals
Acids react with certain metal to produce hydrogen gas
When reaction takes place, the metals seem to disappear (corrode)
Reactions with carbonates
Gas forms from adding carbon and an acid
Reactions with indicators
Litmus paper is an indicator in which changes color
If the litmus paper turns red, it is an acid

30. Properties of Bases
Bases- a substance that tastes bitter, feels slippery, and turns red litmus paper blue
Bitter tastes: tonic water
Slippery feel- think of how your hands feel with water and soap on them
Reactions with indicators- bases turn litmus paper blue
Reactions of bases-does not react with carbon to form a gas

31. Uses of Acids and Bases What are some ways we use them?
Bases: cleaners, baking
Acids: food (tomatoes & oranges), fertilizer, batteries

32. Acids and Bases in Solution
Acids: any substance that produces hydrogen ions in water
Produces one or more hydrogen ions and a negative ion in solution of water
Hydrogen or hydronium ion: atom of hydrogen that has lost its electron
Negative ion: nonmetal or polyatomic ion

33. Example of reaction in water:

34. Bases: any substance that produces hydroxide ions in water
Made of positive ions combined with hydroxide ions
Hydroxide ions: negative ion made of oxygen and hydrogen
Produces a positive ion and a hydroxide ion in a solution of water

35. Example reaction in water:

36. Measuring pH pH scale: range of values from 0-14 pH of 7 is neutral
Expresses the number of hydrogen ions in a solution
Low pH tells you that the concentration of hydrogen ions is high. In contrast, a high pH tells you the concentration of hydrogen ions is low
pH of 7 is neutral
Can determine pH by using an indicator

37. Acid-Base Reactions
Reaction between an acid and a base is called a neutralization
Example reaction:

38. Reactants
Final pH depends on the volumes, concentrations, and identities of the reactants
Products
Salt: ionic compound that can be made from neutralization reaction
Positive ion of base and negative ion of acid
Water: the other product of a neutralization reaction

39. In a neutralization reaction, an acid reacts with a base to produce a salt and water
Example:

40. Digestion and pH
7-5

41. What is digestion?
Food must be broken down into simpler substances that your body can use for raw materials and energy
Digestion: breaks down the complex molecules of foods into smaller molecules
Mechanical digestion
Physical process in which large pieces of food are torn into smaller pieces
Size of food is reduced, but food isn’t changed into other compounds

42. Chemical digestion Breaks large molecules into smaller ones
Using help from enzymes (catalyst that speed up reactions)
Enzymes require the right conditions to work (temperature and pH)

43. pH in the Digestive System
Your mouth
Teeth chew and mash food (mechanical digestion)
Food is mixed with saliva
Saliva contains enzyme, amylase that works best at pH of 7

44. Stomach Mechanical continues
Chemical digestion begins for foods containing protein (meat, fish, & beans)
Cells release enzymes (ex. Pepsin) and hydrochloric acid (pH of 2)

45. Small Intestine Chemical digestion continues
Digestive fluid containing bicarbonate ions surrounds the food (pH of 8)
Contains enzymes that breakdown carbohydrates, fats, and proteins
Large food molecules have been broken down into smaller ones and they pass through the wall of the small intestine into the bloodstream and carried to cells that need them