CHEMICAL REACTIONS - PowerPoint PPT Presentation

Loading...

PPT – CHEMICAL REACTIONS PowerPoint presentation | free to view - id: 702155-ZjY4M



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

CHEMICAL REACTIONS

Description:

CHEMICAL REACTIONS PHYSICAL VERSUS CHEMICAL CHANGE A REFRESHER Physical Change A change that alters the form or appearance of a material but DOES NOT convert the ... – PowerPoint PPT presentation

Number of Views:20
Avg rating:3.0/5.0
Slides: 26
Provided by: BeckyD154
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: CHEMICAL REACTIONS


1
CHEMICAL REACTIONS
2
PHYSICAL VERSUS CHEMICAL CHANGE A REFRESHER
Physical Change A change that alters the form or appearance of a material but DOES NOT convert the material into a new substance.
Chemical Change A change in matter that forms one or more new substances. The new substances) are made of the same elements as the original substance, but are now in different combinations.
3
ATOMS AND MOLECULES
  • Atom is the smallest particle of an element.
  • All atoms of an element have the same chemical
    properties.
  • A molecule is a particle made of two or more
    atoms bonded together.
  • Some molecules are made of the same element
    (example O2 the form of oxygen we breathe)
  • MOST molecules are made of more than one type of
    atom. (example H20 )
  • Try to count the atoms how many total atoms are
    there in 1 molecule of water?

4
MORE ABOUT MOLECULES
  • All compounds are molecules.
  • but NOT all molecules are compounds.
  • Think about it.
  • A compound is a pure substance made up of two or
    more elements.
  • A molecule is two or more atoms.

5
OBSERVING CHEMICAL REACTIONS
  • Chemical Reaction The process in which
    substances undergo chemical changes that results
    in the formation of new substance.
  • How can you tell if a chemical reaction has taken
    place?
  • Evidence for chemical reactions
  • Color change
  • A Precipitate Forms
  • Precipitate is a solid that forms from solution
    during a chemical reaction.
  • Gas is produced (like when you mix baking soda
    and vinegar)
  • Changes in temperature
  • Changes in properties

6
(No Transcript)
7
CHEMICAL REACTION VOCABULARY
  • Look up the definitions for the following terms
    and add to your notes (Page 24-25 or glossary)
  • Symbol, Chemical Formula, Chemical Equation,
    Subscript
  • Symbol In chemistry, a one-letter or two-letter
    set of characters used to identify an element.
  • O, Fe, He, H
  • Chemical formula A combination of symbols that
    represent the elements in a compound.
  • NaCl, CO, CO2
  • Chemical Equation Uses symbols and formulas to
    show the reactants and the products of a chemical
    reaction.
  • Subscripts Show the number of atoms of an
    element in a molecule or the ratio of elements in
    a compound.
  • If a letter doesnt have a subscript the number 1
    is understood to be there.
  • For example, CO2 has 1 atom of Carbon and 2
    atoms of Oxygen, for a total of 3 atoms.

8
STRUCTURE OF A CHEMICAL EQUATION
  • A chemical equation summarizes a chemical
    reaction.
  • The REACTANTS are the materials you have at the
    beginning of the reaction.
  • The PRODUCTS are the new materials that you have
    when the reaction is complete.
  • Chemical equations have a definite structure.
  • The reactants are always on the LEFT, followed by
    an arrow (yields).
  • The products are always on the RIGHT.
  • Reactant Reactant Product
    Product

9
CHEMICAL BONDS AND REACTIONS
  • A Chemical Bond is the force that holds atoms
    together.
  • Think of it like the glue that makes atoms
    stick together.
  • Chemical Reactions occur when chemical bonds
    break or when new bonds form.

10
LAW OF CONSERVATION OF MASS
  • The Law of Conservation of Mass states that the
    amount of matter in a chemical reaction does not
    change. Therefore, the total mass of the
    reactants MUST EQUAL the total mass of the
    products.

11
COUNTING ATOMS
  • Make a 2-column list of the different elements in
    each compound.
  • Write down how many atoms of each element.
  • Add all of the atoms together for a total.
  • Example NaOH
  • Now You Try MgO
  • Did you say Mg 1 and O 1 for 2 Total?

Element of Atoms
Na 1
O 1
H 1 3 Total
12
COUNTING ATOMS WITH SUBSCRIPTS
  • MgCl2
  • Now You Try!
  • C6H12O6

Subscript
Mg 1
Cl 2 3 Total
C 6
H 12
O 6 24 Total
13
COUNTING ATOMS WITH COEFFICIENTS AND SUBSCRIPTS
H 4
N 4
O 12 2o total
  • 4HNO3
  • Coefficient number placed in front of a chemical
    formula in an equation. It tells you how many
    atoms or molecules of each reactant and product
    take place in the reaction.
  • Count Just Like Before
  • List each element.
  • Multiply each element by the coefficient.
  • If the element also has a subscript, multiply the
    coefficient by the subscript.
  • Now You Try!
  • 6 PO4

P 6
O 24
30 total
14
COUNTING ATOMS WITH COEFFICIENTS, SUBSCRIPTS AND
PARENTHESIS
  • Ca (C2H2O2)2
  • Just like before make a chart of all elements in
    the chemical formula.
  • Start with the parenthesis.
  • Count each atom of the elements.
  • Multiple each element by the parenthesis
    subscript.
  • Now You Try Mg(C2H3O2)2
  • What happens if we add a coefficient of 2 in
    front of the entire formula?

Ca 1
C 2 X 2 4
H 2 X 2 4
O 2 X 2 4
TOTAL OF 13 Atoms TOTAL OF 13 Atoms TOTAL OF 13 Atoms TOTAL OF 13 Atoms
15
BALANCING CHEMICAL EQUATIONS
16
(No Transcript)
17
TWO SIDES TO A CHEMICAL EQUATION
  • REACTANTS PRODUCTS
  • Reactants what goes into the chemical rxn
  • Products what comes out of the chemical rxn

18
  • In chemical reactions, new things are made

19
BASIC EQUATION
  • Chemical Equation
  • CO2 H2O C6H12O6 O2
    H2O

20
LAW OF CONSERVATION OF MATTER????
  • Matter cannot be created or destroyed
  • -Look at the equation again, is there the same
    amount of matter on the REACTANTS side as there
    is on the PRODUCTS side? Count the number of
    atoms for each element in the Reactant side and
    the Product side.
  • CO2 H2O C6H12O6 O2
    H2O

C 1
O 3
H 2
C 6
O 14
H 9
21
COUNT THE ATOMS NOW REMEMBER TO MULTIPLY WITH
THE COEFFICIENT!
C 6
O 24
H 24
C 6
O 24
H 24
22
HOW TO BALANCE A CHEMICAL EQUATION
  • Create a list of the atoms of each element just
    as if you are counting atoms.
  • Pick an element that is not equal on both sides
    of the equation.
  • Add a coefficient in front of the formula with
    that element and adjust your original counts.
  • Continue adding coefficients until you get the
    same number of atoms of each element on both
    sides.
  • Update your list (inventory) after every move.
  • Save Oxygen and Hydrogen for last
  • PRACTICE!
  • H2 O2 H2O
  • C Cl2 CCl4

23
DEMONSTRATION - CONSERVATION OF MASS
  • Vinegar baking soda reaction
  • We need to measure the mass of all reactants
    BEFORE the reaction.
  • Vinegar and baking soda
  • After we measure the mass of the reactants you
    should be able to calculate the total mass of the
    product. What would it be?
  • We also need to find the mass of the bag and
    cups. Why?
  • We then need to close the bag to created a closed
    system.
  • Why do you think we need to create a closed
    system by closing the bag? What might be lost if
    we did not close the bag?

24
MORE PRACTICE
  • Complete the front of the balancing act
    worksheet.
  • If you finish, try these

25
LAW OF CONSERVATION OF MASS
  • Open system versus Closed System
  • If a chemical reaction takes place in a closed
    system, no matter can enter or leave the
    reaction.
  • - the reaction takes place in a sealed container
    or in a vacuum.
  • If a chemical reaction takes place in an open
    system, matter can enter or leave during the
    reaction.
  • The reaction DOES NOT take place in a sealed
    container.
About PowerShow.com