1. Compounds, Mixtures, Solutions and Reactions

2. Classifying Matter Matter Pure Substances Mixtures milk, tea Fe, O
Homogeneous
Heterogeneous
Elements
Compounds
Rocky Road ice cream, muddy water
milk, tea
Fe, O
H2O, CO2

3. What is a Pure Substance?
A pure substance is a classification of matter that includes both elements and compounds
Pure substances cannot be separated by physical means such as distillation, filtration, or chromatography

4. Elements We will study elements in depth later, but be sure to know…
An element is made of one kind of atom
Found on the periodic table

5. What Is A Compound?
A compound is a pure substance that is created by 2 or more elements chemically reacting and joining together
Ex: NaCl, H2O, CO2, NH3, NaHCO3, and C6H12O6
Notice that elements combine in many ways to make compounds
Ex: H2O, H2O2, CO, and CO2

6. Why Do Compounds Form?
Compounds form to allow elements to become more stable
Na is flammable when it comes in contact with H2O, and Cl2 is a toxic gas
NaCl is a very stable compound that is neither flammable nor toxic (in normal quantities)
Compounds that are extremely unstable will break down to form the more stable elements

7. How Do Compounds Form?
Compounds form by the interaction between the nuclei and valence electrons of 2 or more elements.

8. What Do Compounds Have To Do With My Life?
Compounds are the substances that make up ALL living and non-living things
Examples: Where would you be without:
H2O—water
NaCl—table salt
C3H8O—rubbing alcohol
C55H98O6—an example of an
unsaturated fat

9. What Is A Mixture?
A mixture is the physical combination of 2 or more substances
It is important to understand that a mixture is not chemically combined
Mixtures can be separated by physical means such as filtration, distillation, and chromatography
Mixtures can be divided into 2 groups
Homogenous mixtures
Heterogeneous mixtures

10. How Do Mixtures Form?
Mixtures form by physically “junking” 2 or more substances together
Remember no chemical change is occurring
The formation of a mixture is not a result of lowering energy

11. What Is a Homogenous Mixture?
A homogeneous mixture is a mixture that is evenly distributed
Homogeneous mixtures are commonly called solutions.
Solution = Solute + Solvent
Solute: “stuff” being dissolved
Solvent: “stuff” doing the dissolving
The solvent is present in greater quantity
The solute is present in the lesser quantity
Ex: Salt water: Salt=solute, Water=solvent

12. What Is a Heterogeneous Mixture?
A heterogeneous mixture is a mixture that is unevenly distributed.
Examples:
Iced tea: The ice is floating at the top and therefore is not evenly distributed throughout the tea
Chex Mix: You may find a different number of pretzels or Chex cereal in each handful; therefore, the mixture is unevenly distributed

13. How Are Mixtures Important To My Life?
We encounter mixtures everywhere in our lives
Where would you be without:
Ice cream
Kool-aid
Shampoo
Soup
Milk
Orange juice

14. Place an S beside each solution and an M beside each mixture
Pop Quiz Question #1
Place an S beside each solution
and an M beside each mixture
_____ seawater
_____ steel
_____ salad
_____ air
_____ handful of confetti S S M S M

15. Rule #1: Usually there is more solvent than solute
Solutions
Solutions can be solids, liquids, or
gases
One substance dissolves in another
--The substance that does the dissolving
*Water is the most common solvent.
solvent
Water is the most common solvent. It can dissolve more substances than any other substance on earth, so its called the universal solvent
solute
--The substance that gets dissolved
Rule #1: Usually there is more solvent than solute

16. What Affects Solubility?
Demo 1: Motion
Rule #2: stirring helps to break up particles and bring particles in contact with the solvent
Demo 2: Particle Size/Surface Area
Rule #3: the smaller the particle, the faster a solute will dissolve
Demo 3: Pressure
Rule #4: For gases, the higher the pressure, the more gas that can be dissolved in a liquid
Demo #1: Sugar sprinkled in bottom of beaker (on overhead) vs. sprinkled on bottom of beaker + stirring
Demo #2: Sugar cube vs. granular sugar (must explain granular)
Demo #3: which is less dense, gas or liquid? Why? (takes up more space). What happens when you first open a soda? (sound of gas escaping, release of pressure). Open the soda. The only way to get all that carbon dioxide gas in the soda is to put the liquid under a lot of pressure. When the pressure escapes, the carbon dioxide gas begins to escape because it is less dense than the liquid. What happens as the soda sits? Gets flat as gas continues to escape.
Demo 4:
A. Stir sugar into room temperature water in beaker. Have hot beaker, can stir in more water.
B. Have two beakers on hot plate—one just boiling water, measure temperature; second with salt in water, measure temperature. 2 water bottles: put salt water in bottle to freeze, should not freeze over night (or check each hour to see when freezes. C.

17. Demo 4: Temperature
Rule #5: increase in the temperature of the solution increases the solubility of a solute
Rule #6: Adding a solute will decrease the freezing point and increase the boiling point
Rule #7: the more solute in a solution, the less additional solute that will dissolve; the more solvent, the more solute can be dissolved

18. Saturated solution: contains the
maximum quantity of solute that can dissolve in a certain quantity of solvent
Supersaturated
Saturated solution: if you try to put sugar in your tea, and some ends up at the bottom, the sugar at the bottom wouldn’t “fit” in the solution---the solution is saturated.
If I raise the temperature of a solution, I can add more and more solute, until it can’t handle anymore

19. Pop Quiz Question #2 Which is the solute? Which is the solvent?
A. salt in water
B. 40% tin in 40% copper
C. strawberries in cream
D. carbon dioxide gas in water

20. Amounts of Solute
A solution’s concentration depends on the amount of solute dissolved in the solvent
A solution with a high concentration has a large amount of solute
A solution with a low concentration of solute is called a dilute solution
Soda bottles with different concentrations of color.

21. Solubility
Solubility is the ability of a substance to dissolve in another substance
It is the amount of substance that will dissolve in a certain amount of solvent at a given temperature
If a solute is highly soluble, a solution will be very concentrated
If a solute has a low solubility, the solution will be dilute
Ask for results to lab—what’s soluble in water?

22. Solutions/Solubility Video
Do p. 545 question 1-4 and p.550 questions 1-4

23. How Can We Change Matter Into New Substances?
Chemical reaction (also known as a chemical change) is a change in a substance or substances that results in a totally new substance
Ex: 2H2(g) + O2(g)  2H2O(g)
Notice that the reactants (the substances you start with) combine to form a new substance (the product)

24. How Do I Know If A Chemical Reaction Has Occurred?
There are 5 indicators of a chemical reaction
Evolution of a gas
Evolution of light
Evolution of heat
Color change
Evolution of a precipitate
Precipitate: an insoluble substance that is produced as result of a chemical reaction

25. Why Do Chemical Reactions Occur?
Chemical reactions occur to produce a more stable product than the existing reactants
Ex: 2Na(s) + Cl2(g)  2NaCl(s)
*The sodium is highly unstable and the chlorine gas is somewhat unstable. The resulting Sodium Chloride is VERY stable.
**It is important to understand that the products have totally different properties than the reactants

26. Where Does The Matter Go?
It is important to understand that when matter undergoes a chemical reaction (ie a chemical change) it does not disappear or appear
The atoms are rearranged and form new bonds, but no matter is lost nor gained
This is called the Law of Conservation of Matter

27. What Kind of Chemical Reactions Do I Experience?
The acidic milk and basic baking soda that produce CO2 gas when a cake bakes
Paper burning to produce ashes, CO2, and H2O vapor
Hydrogen peroxide decomposing to produce water and oxygen gas

28. Exothermic Reactions A reaction in which energy is released
Often produces an increase in temperature
Reactants = Products + Energy

29. Exothermic Examples
Glow sticks- work by a chemical reaction that releases energy as light
Fireflies- light up by a reaction that takes place between oxygen and a chemical called luciferin

30. Endothermic Reactions
A reaction in which energy is absorbed
Often produces a decrease in temperature
Reactants + Energy = Products

31. Endothermic Examples Instant cold pack Photosynthesis
Baking a cake- The cake batter will not bake unless it absorbs energy