1. Substances, Mixtures, and Solubility Chap. 21

2. What is a Solution
Section 1

3. Substance
A substance can’t be broken down into simpler parts by ordinary physical processes (boiling, etc.)
Only chemical processes can change them.

4. Elements
An element is an example of a pure substance; it cannot be broken down into simpler substances.
Iron, Nickel, and Oxygen are all examples of elements.

5. Compounds
Water is not an element. It is an example of a compound which is made of two or more elements that are chemically combined.
The ratio of the atoms in a compound is always the same.

6. Reactants and Products
Whenever reactants are combined, the products must be exactly equal.
For example:
Baking Soda + Vinegar= Carbon Dioxide + Sodium Chloride + Water
(8.7g) (6.2g) = (2.7g) (6.9g) __?__g

7. Mixtures
Mixtures are combinations of substances that can be separated by physical processes. (don’t always have the same proportions).

8. Mixtures
Unlike compounds, mixtures do not always contain the same proportions of the substances that they are composed of.

9. Heterogeneous Mixture
A type of mixture where the substances are not mixed evenly is called a heterogeneous mixture

10. Homogeneous Mixture
A homogeneous mixture contains two or more substances that are evenly mixed.
Another name for a homogeneous mixture is a solution.

11. Solute and Solvent
The substance that dissolves—or seems to disappear—is called the solute.
The substance that dissolves the solute is called the solvent.

12. Types of Solutions
Liquid-Solid—an example of this would be sugar and water.
Liquid-Liquid—This is when two liquids are combined (coffee w/ milk).
Gas-Gas—one gas may be dissolved into another gas (like the air you breathe).

13. Types of Solutions Cont’d
Liquid-Gas—when a gas is mixed w/ a liquid (carbonation in soda)
Solid solution—an example would be two metals.

14. Solubility
Section 2

15. Water—The Universal Solvent
Because water can dissolve so many different solutes, chemists often call it the universal solvent.
A solution in which water is the solvent is called an aqueous solution.

16. Two Types of Bonding Covalent—when compounds share electrons (e-).
Ionic—when compounds do not share e-. (this gives it a negative charge).

17. Ions Atoms with a charge are called ions.
Table salt is ionic, meaning it has a negative charge.

18. Solubility
Solubility is a measurement tells how much solute dissolves in a given amount of solvent.
The solubility of a material has been described as the amount of the material that can dissolve in 100 g of solvent at a given temperature.

19. Solubility Solubility can change depending on temperature.
For example, if you heat water, not only does the sugar dissolve at a faster rate, but more sugar can dissolve in it.

20. Saturation
A solution that contains all of the solute that it can hold under the given conditions is called a saturated solution.
In other words, it can’t possibly hold any more of the solute.

21. Supersaturation
If a saturated solution is cooled slowly, sometimes the excess solute remains dissolved for a period of time.
Such a solution is said to be supersaturated, because it contains more than the normal amount of solute.

22. Acidic and Basic Solutions
Section 3

23. Acids
Acids are substances that release positively charged hydrogen ions, H+, in the water.

24. Properties of Acidic Solutions
Sour taste is one of the properties of acidic solutions.
Another property of acidic solutions is that they can conduct electricity.
Acidic solutions also are corrosive, which means they break down certain substances. Many acids can corrode fabric, skin, and paper.

25. Uses of Acids
Vinegar, which is used in salad dressing, contains acetic acid.
Lemons, limes, and oranges have a sour taste because they contain citric acid.

26. More Uses of Acids
Acids often are used in batteries because their solutions conduct electricity.

27. Bases Basic solutions feel slippery. Bases also taste bitter.
Bases are substances that can accept hydrogen ions (H+).
Basic solutions feel slippery.
Bases also taste bitter.
Like acids, bases are corrosive.

28. Uses of Bases
Bases give soaps, ammonia, and many other cleaning products some of their useful properties.

29. pH pH is a measure of how acidic or basic a solution is.
The pH scale ranges from 0 to 14.
Acidic solutions—pH values below 7.
A solution with a pH of 0 is very acidic.
A solution with a pH of 7 is neutral.
Basic solutions—pH values above 7.

30. pH Scale
A change of 1 pH unit represents a tenfold change in the acidity of the solution.
In other words, a change of 1 on a pH scale means that a solution is 10 times more or less acidic.

31. Periodic Table
The Periodic Table displays all of the elements.

32. Atomic Number
Atomic Number is the number of protons in an atom.
This number is found at the top of an element.

34. Protons
The atomic number is the number of protons in an atom of an element.
Protons are positively charged particles of an element (p+).

35. Neutrons
Neutrons are particles of an element that have no charge (no).

36. Electrons Electrons are negatively charged (e-)
Elements will have the same number of electrons as they have protons.

37. Atomic Weight
The atomic weight is basically a measurement of the total number of particles in an atom's nucleus.
To find atomic weight, you add protons + neutrons.