Compounds, Mixtures, Solutions and Reactions

Classifying MatterMatter

Pure Substances Mixtures

Elements Compounds

Homogeneous Heterogeneous

Fe, O H2O, CO2

milk, tea Rocky Road ice cream, muddy water

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

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

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

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

How Do Compounds Form?• Compounds form by the interaction

between the nuclei and valence electrons of 2 or more elements.

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

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

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

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

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

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

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

Solutions

• Solutions can be solids, liquids, or

gases

• One substance dissolves in another

solvent --The substance that does the dissolving

*Water is the most common solvent.

solute

Rule #1: Usually there is more solvent than solute

--The substance that gets dissolved

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 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

• Saturated solution: contains the

maximum quantity of solute that can dissolve in a certain quantity of solvent−Supersaturated

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

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

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

Solutions/Solubility Video

• http://app.discoveryeducation.com/search?Ntt=solutions+and+solubility&N=18342&N=4294949582&N=4294939055

• Do p. 545 question 1-4 and p.550 questions 1-4

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)

How Do I Know If A Chemical Reaction Has Occurred?

• There are 5 indicators of a chemical reaction

1. Evolution of a gas2. Evolution of light3. Evolution of heat4. Color change5. Evolution of a precipitate

Precipitate: an insoluble substance that is produced as result of a chemical reaction

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

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

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

Exothermic Reactions

• A reaction in which energy is released

• Often produces an increase in temperature

• Reactants = Products + Energy

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

Endothermic Reactions

• A reaction in which energy is absorbed

• Often produces a decrease in temperature

• Reactants + Energy = Products

Endothermic Examples

• Instant cold pack

• Photosynthesis

• Baking a cake- The cake batter will not bake unless it absorbs energy