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Chemical Reactions
Chemical Reactions
Chemical Reactions
Chemical Reactions
Chemical Reactions
Chemical Reactions
Chemical Reactions
Chemical Reactions
Chemical Reactions
Chemical Reactions
Chemical Reactions
Chemical Reactions
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Chemical Reactions


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  • chalk = calcium carbonite (CaCH3) ammonia = NH3
  • Like the days of the month, the chemical elements can be arranged in a way that shows a repeating, or PERIODIC pattern. DRY ERASE EXERCISE Patterns: atomic # increases as you move left to right Groups share same # of valence electron Energy levels increase as you move down a group
  • Remember: a substance is an element or compound. New elements are not FORMED in reactions. ***The (g) is for gas and (l) is for liquid coefficients tell how many molecules of each substance are involved in each reaction - no coefficient means there is just ONE molecule
  • C 6 H 12 O 6 + O 2 = CO 2 + H 2 O is the reaction in your body's cells that turn sugar and oxygen into usable energy (ATP), with CO2 and water as waste products ***reaction is reversed in plants (sugars are created from water and CO2 with sunlight's energy) OFTEN A TRIAL AND ERROR PROCESS TO GET THINGS BALANCED
  • A catalyst is a substance that speeds up a reaction without being used up itself . Here is an example of a reaction with a catalyst. Hydrogen peroxide decomposes (falls apart) to form water and oxygen gas: hydrogen peroxide —> water + oxygen This reaction only occurs very slowly unless we add the compound manganese oxide that acts as a catalyst for this reaction. When the catalyst is added the reaction speeds up greatly but the manganese oxide never runs out. How does a catalyst work? 1) A catalyst provides a surface on which the reaction can take place. This increases the number of collisions between the particles of the substances that are reacting. 2) A catalyst lowers the activation energy (the minimum amount of energy needed for a reaction to take place). This means that the particles can react with less energy than they needed before the catalyst was added. If we lower the amount of energy needed for particles to react, then more particles can react .
  • C 3 H 8 = propane
  • Transcript

    • 1. Chemical Reactions Basic Chemistry Heartlife Physical Science
    • 2. Reading The Periodic Table - Review
      • What is this and what does it tell you?
        • the atomic number
        • # of protons (& electrons)
      • What is this number and what does tell you?
        • the atomic mass (in amu's)
        • weight of combined protons & neutrons
        • lets you calculate the # of neutrons by subtracting the atomic number
      • What is this called?
        • atomic symbol ( abbreviation of element name)
        • allows easier written chemical formulas
          • H 2 O 2 , CO 2 , C 6 H 12 O 6
      • Describe an electron.
        • Carries a negative charge.
        • Very tiny - has virtually no mass.
        • Orbits around the nucleus in energy levels.
    • 3.
      • What are the columns of the periodic table called?
      • What do elements in the same group have in common?
        • similar chemical & physical properties
        • same # of valence electrons
      • What are the rows of the periodic table called?
      • What do the periods show us?
        • highlight the repeating nature of elements (periodicity)
          • arranged in order of increasing atomic number (no other similarities)
      Periodic Table Arrangement - Review
      • groups (family)
      • periods
      • What are the 3 main types of elements?
        • Metals
        • Metalloids
        • Nonmetals
      • In which state of matter are most elements found at room temperature?
        • Solid
    • 4. Review - Chemical Bonding
      • What are two ways to draw an atom?
        • Bohr Model - ALL electrons orbiting an atom
          • # of protons & neutrons in center
        • Lewis Dot Structures - ONLY the valence electrons
      • A bond where electrons are SHARED by two atoms:
      • An electron is transferred, forming charged atoms that are then attracted due to their electrical charges:
        • IONIC BOND (ions are formed)
      • What makes for a happy atom (stable/unreactive)?
        • full energy levels (filled valence electron shell)
        • paired electrons
      • What elements make up the Alkali Earth Metals?
        • Berryllium, Magnesium, Calcium, Strontium, Barium, Radium
      • What elements make up the Halogens?
        • Fluorine, Chlorine, Bromine, Iodine, Astatine
      Sr H H H H
    • 5. Another type of Bonding - Metallic Bonds
      • How many valence electrons do most metals have?
        • 1, 2, or 3
      • These electrons are not held tightly, so they often escape
        • Resulting atoms are positive ions (+1, +2 or +3 charge)
        • Free electrons tend to float around in a constantly moving "sea"
      • The pooled electrons zoom around the positive ions
        • Give metals their unique traits
        • pass on heat & electricity easily (conductivity)
        • slide past one another easily (malleability)
      • usually occur in pure metallic elements, like aluminum
    • 6. Chemical Reactions
      • A chemical reaction occurs when two or more substances interact to form new substances
        • reactants : the substances that interact in a chemical reaction
        • products : the new substances from due to the chemical reaction
        • reactants products
        • H 2 + Cl 2 2HCl 2H 2 + O 2 2H 2 O
      reactants product
        • a diatomic molecule is a molecule made of two atoms
        • hydrogen (g) + chlorine (g) hydrochloric acid (l)
        • hydrogen (g) + oxygen (g) water (l)
    • 7. Conservation of Mass & Energy
      • Matter (made of atoms) cannot be created or destroyed.
        • Law of Conservation of Mass
      • During chemical reactions, changes will occur, but
        • no atoms can ever cease to exist
        • no atoms can ever come from nothing
        • atoms can only be rearranged into different forms or substances
      • Also true for energy
        • Energy cannot be created or destroyed.
        • change forms (see picture)
        • move from one place to another
    • 8. Balancing Chemical Equations
      • What do you notice about reactants & products in this reaction?
        • Fe + Cl 2 = FeCl 3
          • total # of iron atoms in the reactants: 1
          • total # of chlorine atoms in reactants: 2
      • To make it equal on both sides, coefficients are added to balance the equation.
        • 2 Fe + 3 Cl 2 = 2 FeCl 3
      • Let's try another one:
        • C 6 H 12 O 6 + O 2 = CO 2 + H 2 O
        • C 6 H 12 O 6 + 6 O 2 = 6 CO 2 + 6 H 2 O
      ferric chloride
    • 9. Steps to Balancing an Equation
      • Example: Balance the equation that takes place when sodium hydroxide reacts with sulfuric acid to form sodium sulfate and water.
      Chemical Reactions Check to be sure you have the same number of atoms of each element on both sides of the equation. Step 4 Try coefficients that will balance the equation. - Start with elements that appear only once on each side of the equation. - Never change the subscripts in a chemical formula. Step 3 Count the number of atoms of each element on each side of the equation. (use a table to keep track) Step 2 Identify reactants & products and write their chemical formulas on the appropriate sides of the equation. Step 1
    • 10. More Practice
      • Balance the equation that takes place when methane gas reacts with oxygen to form carbon dioxide and water.
      • Step 1: CH 4 + O 2 CO 2 + H 2 O
      • Step 2:
      • Step 3: CH 4 + 2 O 2 CO 2 + 2 H 2 O
      • Step 4:
      After Before Element 3 2 O 2 4 H 1 1 C After Before Element 4 4 O 4 4 H 1 1 C
    • 11. Reaction Rates
      • Collision Theory : substances cannot react unless their particles come in contact with one another
        • the more they collide, the more likely they'll react (faster rate)
        • the slower the particles move, the less likely they'll collide and thus react (slower rate)
      • Factors affecting the rate of reaction:
        • Concentration
          • more reactants per volume increases the number of particle collisions
        • Temperature
          • heat makes particles move faster
        • Surface Area
          • a spread-out solid increases the chances for liquid or gas to come in contact with it
        • Catalysts
          • lower the energy needed to get a reaction started ( activation energy )
      Temperature & Surface Area Demo
    • 12. Types of Chemical Reactions
      • Synthesis : two or more substances combine to form a new substance
        • A + B  AB
        • examples: photosynthesis, formation of rust and table salt
      • Decomposition : one substance breaks down into two or more simpler substances
        • AB  A + B
        • examples: rotting leaves, electrolysis of water
      • Combustion : a substance combines with elemental oxygen and produces heat
        • C 3 H 8 + 5 O 2  3 CO 2 + 4 H 2 O
        • examples: burning wood, coal or gas, fireworks
      • Displacement : an atom in a compound is replaced by a different atom
        • A + BC  B + AC
          • useful for separating a particular element from a compound
          • examples: silver from silver nitrate Cu + 2 AgNO 3  Cu(NO 3 ) 2 + 2 Ag
      Single Displacement Example