Chapter 13.2. Standards: GLE 0807.9.4 – Distinguish among elements, compounds, and mixtures. GLE...
-
Upload
sarah-park -
Category
Documents
-
view
227 -
download
6
Transcript of Chapter 13.2. Standards: GLE 0807.9.4 – Distinguish among elements, compounds, and mixtures. GLE...
Balancing Equations
Chapter 13.2
Standards:
• GLE 0807.9.4– Distinguish among elements, compounds, and
mixtures.• GLE 0807.9.9– Explain the law of conservation of mass
• GLE 0807.9.8– Interpret the events represented by a chemical
equation
Key concepts:
• Interpret and write simple chemical formulas• Identify the reactants and products of a
chemical reaction.
Key Vocabulary:
• Reactant• Product• Law of conservation
of mass
What do you already know?
• Where do you find reactants? • Where do you find products?• Why do we use symbols instead of
writing out everything?• What does conservation mean?
Now imagine having to write out names!
Let’s talk compound vs. element:
• Is it a compound or element?
He
Let’s talk compound vs. element:
• Is it a compound or element?• How many atoms?
CO2
Let’s talk compound vs. element:
• Is it a compound or element?• How many atoms?
NaClO
Chemical Reaction:
• Chemical equation uses symbols and formulas to describe a chemical reaction.
• Parts:– Reactants—starting materials– Products—what you make– Yield—this is the arrow sign• This usually means that energy is going
in or out
Think of this a piece of sheet music...
Cheat sheet time!
Reactants point to products
R P
Balancing Equations:
• Conservation means the before is equal to the after…meaning whatever we do to the reactants, we must do to the products.
• All atoms must be equal• Law of conservation of mass states
that the mass is neither created nor destroyed in a chemical change. – Reactants = Products
How many atoms?-H20-C6H1206
-CH4
R P
Balancing the Parts:
• Important parts:– Coefficient: the number that is place
in the front of a symbol• This is what WE will use to balance the
equation
– Subscripts• Number written below and to the right
of the symbol
How many atoms?-H20-C6H1206
-CH4
Balancing the Parts:• How to balance:
1. Determine the number of atoms for each element
2. Pick an element that is not equal on both sides (start with metals)
3. Add a coefficient in front the formula with that element and adjust your counts
4. Continue to add coefficients to get the same number of atoms of each side
Remember to keep track of the atoms!
Practice times
Balancing Equations
• Hydrogen and oxygen are diatomic elements.
• Their subscripts cannot be changed.• The subscripts on water cannot be
changed.
Hydrogen + oxygen water
H2 + O2 H2O
Balancing Equation
• Count the atoms on each side.–Reactant side: 2 atoms H and 2
atoms O–Product side: 2 atoms H and 1
atom O
H2 + O2 H2O
Balancing Equations
•H2 + O2 H2O
• If the subscripts cannot be altered, how can the atoms be made equal?
• Adjust the number of molecules by changing the coefficients.
Balancing Equations
• Reactants: 2 atoms of H and 2 atoms of O
• Products: 4 atoms of H and 2 atoms of O
• H is no longer balanced!
H2 + O2 2H2O
Balancing Equations
• Reactant side: 4 atoms of H and 2 atoms of O
• Product side: 4 atoms of H and 2 atoms of O
• It’s Balanced!
2H2 + O2 2H2O
Balancing Equations
• Count atoms.–Reactants: 2 atoms N and 2 atoms
H–Products: 1 atom N and 3 atoms of
NH3
N2 + H2 NH3
Nitrogen + hydrogen ammonia
Balancing Equations• Nothing is balanced.• Balance the nitrogen first by
placing a coefficient of 2 in front of the NH3.
N2 + H2 2NH3
Balancing Equations• Hydrogen is not balanced.• Place a 3 in front of H2.
• Reactant side: 2 atoms N, 6 atoms H
• Product side: 2 atoms N, 6 atoms HN2 + 3H2 2NH3
We need practice!
• On the back of your notes, let’s practice.• Do not write on the hand-outs. I will take
these up when you leave.– Balancing Act
Pearls of Wisdom:
• How do you balance equations?• What are some important steps?
Homework:
• Finish your worksheet.