1. Acids, Bases, and Solutions

2. Understanding Solutions
A solution is a mixture with its particles uniformly spread throughout a solvent
A solvent is the part of the solution that dissolves other substances
The solute is a substance that is dissolved by the solvent

3. A solution has the same properties throughout
It contains solute particles (molecules) that are too small to see and are suspended in the solvent
Sugar dissolved in coffee is an example of a solution
The coffee is the solvent and the sugar is the solute
Solvent is water
Solutes are sugar and flavoring

4. Salutes in a solution seem to disappear when they are mixed in a solvent
When a solution forms, particles of the solvent surround and separate the particles of the solute

5. Solutes and solvents have different physical properties such as boiling point, melting point, color, size, density, and others
Physical changes do not change the chemical properties of a substances
Physical changes can often be undone to recover the original materials

6. Dissolving a solute into a solvent is an example of a physical change
Physical properties can be used to recover the solute from the solvent
Suppose you dissolve salt into water
Because water has a lower boiling point than salt, the water can be boiled off leaving the salt behind

7. Solutes have various affects on solvents
The addition of solutes to a solvent can lower its freezing point or raise its boiling point
Ordinarily, the freezing point of water is 0°C
By adding salt to water, the freezing point can be lowered to -4oC (That’s why salt is spread on roads to lower the freezing point in the winter…Oh! That’s right…California doesn’t have icy roads!

8. When liquid water freezes with the solute particles (salt) in it, the solute particles make it harder for the water molecules to form ice crystals
The temperature must drop lower than 0°C for The solution to freeze
Therefore, the presence of a solute in water lowers the freezing point of the water

9. The same is true for increasing the boiling point
Solutes like salt raise the boiling point of water
In a water solution, some of the molecules are water and others are particles of the solute
The water molecules in a solution now need more energy to reach the boiling point
By adding salt to the water decreases cooking time for food because the water is hotter

10. Car manufacturers make use of solutes to protect engines from heat and cold
The coolant in a car’s radiator is a solution of water and another liquid called anti-freeze
The mixture of the two liquids has a higher boiling point and lower freezing point then water alone
The solution can reduce the risk of damage to the car from freezing and overheating

11. In many common solutions, the solvent is water
Water dissolves so many substances that it is called The "universal solvent"
For example, water is the solvent for sodas
Food coloring, carbon dioxide, sugar, and flavoring are the solutes

12. Life depends on water solutions
Nutrients used by plants and animals are dissolved in water within the cells
Water is the solvent in blood, saliva, and tears

13. Many solutions are made with solvents other than water
A solution may be a combination of gases, liquids, or solids
For example
Gasoline is the solution of several different liquid fuels
Alloys are solutions of different metals
Air is a solution of different gases

14. Colloids and Suspensions
Not all mixtures are solutions
Colloids and suspensions are mixtures that have different properties than solutions
A colloid is a mixture that contains small, undissolved particles too small to be easily seen , but big enough to scatter light trying to pass through it
Because the particles scatter the light, it is impossible to see through the mixture
Milk is a colloid

15. A suspension is a mixture in which particles can be seen suspended (held up) in a liquid or gas
The particles can be easily separated by settling or filtration
The particles are visible and larger than the particles in solutions or colloids
Snow globes and salad dressings are examples of suspensions

16. Ionic and Molecular Compounds in Solutions
When an ionic compound mixes with water, the positive and negative ions are attracted to the polar water molecules
Water molecules surround each ion as the ions leave the surface of the compound
As each layer of the compound is exposed, more ions can dissolve
Ions - - - - - - + + + + + + O + O + - -
Water molecule - - - - -

17. Not every substance breaks into ions when dissolved in water
A molecular compound, such as sugar, breaks up into individual neutral molecules
The polar water molecules attract the slightly taller sugar molecules
This causes the sugar molecules to move away from each other
The covalent bonds within the molecules remain unbroken

18. Solutes and Conductivity
Supposed to have a water solution, but you don't know if the solute is salt or sugar
A solution of ionic compounds (salt) conducts electricity
A solution molecular compounds (sugar) does not
If the solution does not conduct electricity, no ions are present which means you have a sugar solution
Salt or Sugar?

19. Concentration and Solubility
Concentration is the amount of solute in a solvent
The more solute, the greater the concentration
It takes approximately 43 gallons of maple sap to make 1 gallon of maple syrup
In order to get the sap sweet enough for pancake syrup, the water (solvent) in the sap must be removed to make a sweeter solution

20. Fruit juices are sometimes packaged as concentrates
To make the concentrate, water (solvent) is removed from the natural juice
When you prepare the juice to drink, you dilute the concentrate by adding back the water

21. Measuring Concentration
To measure concentration, you compare the amount of solute to the total amount of the solution
Concentration is measured as a percent of solute in the solution by volume or mass
The mass of a solute or solvent is measured in grams
The volume of a solute or solvent is measured in milliliters or liters

22. Solubility
Solubility is the measure of how much solute can dissolve in a solvent at a given temperature
There is a maximum amount of solute that can be dissolved in a solvent before the solvent becomes saturated and no more solute can dissolve

23. Working with Solubility
You can identify a substance by its solubility
Solubility is a property of matter
If you had a white powder and could not tell if it was salt or sugar, you could identify it by its solubility
Salt dissolves faster because salt molecules are smaller than sugar molecules
Sugar

24. Factors Affecting Solubility
The solubility of solutes change when conditions change
The factors that affect solubility of a substance include PRESSURE, the TYPE of SOLVENT, and TEMPERATURE
Example: Sugar will dissolve faster in hot tea than ice tea
A sugar solution will become saturated (no more sugar will dissolve) in ice tea faster than hot tea
Hot tea will dissolve much more sugar than ice tea before becoming saturated

25. Pressure Increasing the pressure increases the solubility of gases
Soda water contains dissolved carbon dioxide gas
To increase the carbon dioxide concentration in the solution, the gas is added under high-pressure
Opening the bottle releases the pressure and makes the hissing sound you hear

26. Scuba divers must be aware of the effects of pressure on gases
When divers breath compressed air, nitrogen from the air dissolves in their blood
More dissolves as they go deeper
If divers return to the surface too quickly, nitrogen bubbles form in the blood and block blood flow and divers double over in pain, which is why this condition is sometimes called “The Bends"

27. Solvents Some solvents and solutes are not compatible
Your vinegar and oil salad dressing has to be shaken because vinegar and oil do not mix
When you stop shaking the dressing, it quickly separates into layers of vinegar and oil

28. For liquid solutions, the solvent affects how well a solute dissolves
Polar compounds are molecules that have a positive charge on one side and a negative charge on the other side
Polar compounds dissolve in polar solvents
Nonpolar compounds do not dissolve in polar solvents Example—
Polar water-based paints clean up with soap and polar water
Nonpolar oil-based paints require a nonpolar solvents such as turpentine

29. Waterand oil do not mix because water is a polar compound and oil is nonpolar
Polar compounds a nonpolar compounds do not mix

30. Temperature Solubility increases as the temperature increases
Example— At room temperature, not much sugar can dissolve in water
The solubility of sugar in g of water changes from 180g at 0°C, to g at 25°C, to g at 100°C

31. Unlike most solids, gas in a liquid becomes less soluble when the temperature of the liquid increases
Example— More carbon dioxide will dissolve in cold water than hot water
Warm soda taste "flat“ because warm soda contains less carbon dioxide
Fish love cold water because cold water can hold more oxygen

32. Describing Acids and Bases
Properties of Acids
Acids are compounds whose properties include the kinds of reactions they undergo
An acid tastes sour, reacts with metals, carbonates, and turns blue litmus paper red

33. Reactions with Indicators
Litmus paper is called an indicator
It is made by coating strips of paper with Litmus which is made from plants
Acids turn blue litmus paper red
Other color litmus papers are used to indicate other substances

34. Some common acids are hydrochloric acid, nitric acid, sulfuric acid, carbonic acid, and acetic acid

35. Sour taste
Citrus fruits lemons, grapefruit, oranges, and limes all contain citric acid
Other fruits (cherries, tomatoes, apples) and many other types of foods contain acids, too

36. Scientists never taste chemicals in order to identify them
You should never taste a substance unless you know it is safe to eat

37. Reactions with Metals
Acids react with certain metals, such as magnesium, zinc, and iron, to produce hydrogen gas
When they react, the metals seem to disappear in the acid solution
This observation is one reason acids are described as corrosive, meaning they "wear away" other materials

38. Reactions with Carbonates
A product of an acid's reaction with a carbonate is carbon dioxide
Geologists use this property of acids to identify rocks containing limestone
Limestone is a compound that contains the carbonate ion
If you pour hydrochloric acid on limestone, bubbles of carbon dioxide appear on the rock's surface

39. Properties of Bases
Bases are another group of compounds that can be identified by their properties
A base tastes bitter, feels slippery, and turn red litmus paper blue
Common bases include sodium hydroxide, calcium hydroxide and ammonia
Red = Acid
Blue = Base

40. Bitter Taste Bases are bitter
The slight bitterness of soda is caused by the base quinine
Soaps, shampoos and detergents are bitter too, but they are NOT safe to taste

41. Slippery Feel The slippery feel is a characteristic of bases
Remember, don’t touch anything that you don’t know what it is
Strong bases can irritate or burn your skin
A safer way to identify bases is by using an indicator like litmus paper

42. Reactions with Inhibitors
Since litmus paper can be used to test acids it can also be used to test bases
Bases turn red litmus paper blue
Litmus paper gives a reliable, safe test

43. Uses of Acids and Bases Acids and bases are almost everywhere
Manufacturers, farmers, and builders are only some people who depend on acids and bases in their work
Some acids are vitamins, including vitamin C and folic acid

44. Vitamins are essential in small amounts to normal growth and functioning of the body
Many cell processes also produce acids as waste products
for example— Lactic acid builds up in your muscles when you make them work too hard

45. Acids and Bases in Solution
Acids in solution
A hydrogen ion (H+) is an atom of a hydrogen that has lost its electron
Hydrogen ions are the key to the reaction of acids

46. Acids in a water solution produce positive hydrogen ions
These hydrogen ions form the properties of acids for example— When acid interacts with certain metal atoms, hydrogen gas (H2) is produced
Hydrogen ions also react with blue litmus paper, turning it red

47. Bases in solution Not all bases contain hydroxide ions
for example— the gas ammonia does not, but in solution, ammonia will react with water to form hydroxide ions
A base produces hydroxide ions in water
Hydroxide ions are responsible for the bitter taste and slippery feel of bases, and turn red litmus paper blue

48. Strength of acids and bases
The strength of acids and bases refers to how well an acid or a base produces ions in water
With a weak acid, very few ions form in solution
At the same concentration, a strong acid produces more hydrogen ions
Examples of strong acids include hydrochloric acid, sulfuric acid, and nitric acid
Most other acids, such as acetic acids are weak

49. Measuring pH
Knowing the concentration of hydrogen ions is the key to knowing how acidic or basic a solution is
To describe the concentration of ions, chemist use a numeric scale called the pH scale
The pH scale is a range of values from 0 to 14

50. Most acidic items are at the low-end of the pH scale
A pH lower than 7 is acidic
The most basic items are at the high-end of the scale
A pH higher than 7 is basic
If the pH is 7, the solution is neutral
That means it's neither an acid nor a base
Pure water has a pH of 7

51. A low pH indicates that the concentration of hydrogen ions is big
In contrast, a high pH indicates that the concentration of hydrogen ions is low
If you keep these ideas in mind, you can make sense of how the scale works

52. The pH of a solution can be determined by use of pH paper
pH paper turns a different color for each pH value
Matching the color the paper with the color of the test scale indicates how acidic or basic the solution is

53. Some indicator solutions will change color over the entire pH scale other indicators solutions only change color within a range of approximately two pH units
Knowing the pH range over which this color change occurs gives you a rough estimate of pH
Most chemistry laboratories contain a pH meter that makes rapid pH measurements

54. Using acids and bases safely
Even a dilute solution of hydrochloric acid can eat a hole in your clothing
In order to handle acids and bases safely, you need to know both their strengths and their concentration

55. Acid-base reactions
After neutralization, an acid or base solution is less acidic or basic than either of the starting solutions
The pH depends on the type, the volume, and the concentration of the reactants
A solution with a small amount of strong base reacting with a much larger amount of strong acid will remain acidic
When mixing a solution of strong acid containing hydrogen ions and a solution of strong base containing an equal amount of hydroxide ions a neutral solution will be the result

56. "Salt" may be a familiar name of the stuff you sprinkle on food
But to a chemist a salt is any compound made from the neutralization of an acid with a base
A salt is made from the positive ions of a base and the negative ions of an acid
One product of a reaction of nitric acid with potassium hydroxide (base) is neutral water

57. The other products is potassium nitrate, and salt
Potassium nitrate is soluble in water
Some salts are insoluble and form precipitates