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Compounds, Mixtures, and Reactions. Unit II-Part 5. Classifying Matter. Matter. Pure Substances. Mixtures. Homogeneous. Heterogeneous. Elements. Compounds. Rocky Road ice cream, muddy water. milk, tea. Fe, O. H 2 O, CO 2. What is a Pure Substance?. - PowerPoint PPT Presentation
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Compounds, Mixtures, and Reactions
Unit II-Part 5
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 cannot be separated by physical means.
• It is a classification of matter that includes both elements and compounds
Elements
• We have already studied elements−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)
Can a compound be reversed?
http://www.youtube.com/watch?v=OTEX38bQ-2w “Breaking Down Water”- Anode: The anode of a device is the
terminal where current flows in from outside.
- Cathode: The cathode of a device is the terminal where current flows out.
How Do Compounds Form?• Compounds form by the interaction
between the nuclei and valence electrons of 2 or more elements
• THE OCTET RULE: an element is most stable with 8 valence electrons−Elements will join chemically to
get 8 valence electrons
What Do Compounds Have To Do With My Life?
• Compounds are the substances that make up ALL living and non-living things
• http://www.pslc.ws/mactest/level1.htm
• 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
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: liquid it is dissolved into
• 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
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 (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