1. Describing Chemical Reactions

2. Learning Targets You will:
Identify if a chemical reaction has occurred.
Write a balanced chemical equation from a chemical reaction sentence or word problem.

3. How is cooking muffins like a chemical reaction?
Cooking food always involves a chemical reaction.
Ingredients are mixed and produce muffins.
Reactants yield products
Chemists use a chemical equation to convey as much information as possible about what happens in a chemical reaction.
You will identify if a chemical reaction has occurred.
You will write a balanced chemical equation from a chemical reaction sentence or word problem.

4. You will identify if a chemical reaction has occurred.
Word Equations
Reactants are written on the left and separated by plus signs
Products are written on the right and separated by plus signs
An arrow separates the reactants and products
The arrow reads as yields, gives, or reacts to produce
You will identify if a chemical reaction has occurred.
You will write a balanced chemical equation from a chemical reaction sentence or word problem.

5. You will identify if a chemical reaction has occurred.
Tips
MUST have correct nomenclature
REMEMBER diatomic molecules
Leave space for coefficient in front of each reactant and product
Use physical states and symbols when applicable
Most elements are solid in natural state
Bromine and mercury are liquid in natural state
Hydrogen, nitrogen, oxygen, fluorine, chlorine and noble gases are gas in natural state
You will identify if a chemical reaction has occurred.
You will write a balanced chemical equation from a chemical reaction sentence or word problem.

6. You will identify if a chemical reaction has occurred.
Example
Hydrochloric acid reacts with solid sodium hydrogen carbonate. The products formed are aqueous sodium chloride, water, and carbon dioxide gas. Write an unbalanced equation for this chemical reaction.
__ HCl (aq) + __ NaHCO3 (s)  __ NaCl (aq) + __ H2O (l) + CO2 (g)
You will identify if a chemical reaction has occurred.
You will write a balanced chemical equation from a chemical reaction sentence or word problem.

7. You will identify if a chemical reaction has occurred.
Try on your own
Sulfur burns in oxygen to form gaseous sulfur dioxide. Write an unbalanced equation for this chemical reaction.
__ S (s) + __ O2 (g)  __ SO2 (g)
Write a sentence that describes this chemical reaction:
__ Na (s) + __H2O (l)  __ NaOH (aq) + __ H2 (g)
Solid sodium reacts with liquid water to produce aqueous sodium hydroxide and hydrogen gas.
You will identify if a chemical reaction has occurred.
You will write a balanced chemical equation from a chemical reaction sentence or word problem.

8. You will identify if a chemical reaction has occurred.
Try on your own again …
Solid mercury (II) oxide decomposes to produce mercury and oxygen.
__ HgO (s)  __ Hg (l) + __ O2 (g)
Carbon reacts with oxygen to form gaseous carbon dioxide.
__ C (s) + __ O2 (g)  __ CO2 (g)
You will identify if a chemical reaction has occurred.
You will write a balanced chemical equation from a chemical reaction sentence or word problem.

9. Balancing Chemical Equations
The law of conservation of mass states that mass is neither created nor destroyed.
In order to show that mass is conserved during a reaction, a chemical equation must be balanced.
Coefficients are used to balance a chemical equation — small whole numbers that are placed in front of the formulas in an equation in order to balance it.
MUST be in simplest whole number ratio!
You will identify if a chemical reaction has occurred.
You will write a balanced chemical equation from a chemical reaction sentence or word problem.

10. You will identify if a chemical reaction has occurred.
Balancing activity
Obtain an iPad and go to the following link,
Search and select “balancing chemical equations” simulation
Hit play and work through the introduction
Work through make ammonia, separate water and combust methane
When complete with the introduction hit the game icon at the bottom and work through all three levels
Report your score for each level to me
You will identify if a chemical reaction has occurred.
You will write a balanced chemical equation from a chemical reaction sentence or word problem.

11. Balancing Chemical Equations
No one solid way to balance
Some may:
balance by sight
follow a strict order
make a table
whatever the method, # of atoms going into the equation should = # of atoms going out of the equation.
Helpful tips:
H2O may also be thought of as HOH.
Balance polyatomic ions as groups ONLY if they exist on BOTH sides of the equation
Leave hydrogen and oxygen last to balance (ESPECIALLY true w/combustion reactions)
You will identify if a chemical reaction has occurred.
You will write a balanced chemical equation from a chemical reaction sentence or word problem.

12. You will identify if a chemical reaction has occurred.
Example
Students suspended copper wire in an aqueous solution of silver nitrate. They noticed a deposit of silver crystals on the copper wire when the copper reacted with the silver nitrate. They recorded the equation for this reaction but didn’t balance it. Balance their equation:
__ AgNO3(aq) + __ Cu(s) → __ Cu(NO3)2(aq) + __ Ag(s)
2 AgNO3(aq) + __ Cu(s) → __ Cu(NO3)2(aq) + 2 Ag(s)
You will identify if a chemical reaction has occurred.
You will write a balanced chemical equation from a chemical reaction sentence or word problem.

13. You will identify if a chemical reaction has occurred.
Try on your own
Balance the equation:
__ Al (s) + __ O2 (g)  __ Al2O3 (s)
4 Al (s) + 3 O2 (g)  2 Al2O3 (s)
Balance the following equation:
__ Fe2O3 (s) + __ H2 (g)  __ Fe (s) + __ H2O (l)
Fe2O3 (s) + 3 H2 (g)  2 Fe (s) + 3 H2O (l)
You will identify if a chemical reaction has occurred.
You will write a balanced chemical equation from a chemical reaction sentence or word problem.

14. You will identify if a chemical reaction has occurred.
Try on your own again …
Balance the following equations:
__ SO2 (g) + __ O2 (g)  __ SO3 (g)
__ P (s) + __ O2 (g)  __ P4O10 (s)
__ Al (s) + __ N2 (g)  __ AlN (s)
2 SO2 (g) + __ O2 (g)  2 SO3 (g)
4 P (s) + 5 O2 (g)  __ P4O10 (s)
2 Al (s) + __ N2 (g)  2 AlN (s)
You will identify if a chemical reaction has occurred.
You will write a balanced chemical equation from a chemical reaction sentence or word problem.

15. You will identify if a chemical reaction has occurred.
Put it all together …
Write and balance equations for the following reactions:
Iron metal and chlorine gas react to form solid iron (III) chloride.
Solid aluminum carbonate decomposes to form solid aluminum oxide and carbon dioxide gas.
Solid magnesium reacts with aqueous silver nitrate to form solid silver and aqueous magnesium nitrate.
You will identify if a chemical reaction has occurred.
You will write a balanced chemical equation from a chemical reaction sentence or word problem.

16. You will identify if a chemical reaction has occurred.
Check yourself …
2 Fe (s) + 3 Cl2 (g)  2 FeCl3 (s)
Al2(CO3)3 (s)  Al2O3 (s) + 3 CO2 (g)
Mg (s) + 2 AgNO3 (aq)  2 Ag (s) + Mg(NO3)2 (aq)
You will identify if a chemical reaction has occurred.
You will write a balanced chemical equation from a chemical reaction sentence or word problem.

17. SUMMARIZE … You will: Identify if a chemical reaction has occurred.
Write a balanced chemical equation from a chemical reaction sentence or word problem.