Did the copper disappear in yesterday's lab? When you eat a bowl of ice cream, it disappears--but where does it go? How about gas in the tank of a car?
Even though the original form of a material may disappear, the atoms that compose them remain!
In our lab activity, the copper pennies became coated with zinc! The copper mixed with zinc to become brass. The original copper and zinc atoms were not changed.
In your car, the carbon and hydrogen molecules in the gas reacts with air to create carbon monoxide, carbon dixoide and water. These leave through the car's exhaust system. The original atoms are not destroyed, just rearranged.
"Using things up" means chemically changing materials, not destroying them.
The law of conservation of matter says in a chemical reaction, matter is neither created nor destroyed.
Chemical equations must be balanced so that you don't end up with more than you started with.
C + O2 --> CO2
coal and oxygen react to carbon dioxide
produce
(Reactants) (Products)
All atoms appearing in the products originally came from the reactants.
Cu + O2 --> Cu2O
This is not an equation because it is not balanced.
Because a unit of Cu2O contains only one atom of oxygen, two units of Cu2O must form.
Cu + O2 --> 2Cu2O
How many copper atoms are needed to produce these two units of Cu2O?
4Cu + O2 --> 2Cu2O
This is the completed equation.
The numbers placed in front of the chemical symbols or formulas are called coefficients.
Atom inventories help confirm that a chemical equation is balanced. Count the atoms of each element on each side of the euqation.
Reactant side Product side
4 Cu 4 Cu
2 O 2 O
Begin Your Turn on p. 95
Questions? Comments??
Amanda Noland