Chemical Changes
Monroe 1-9-09
What are the parts to a chemical formula?
Coefficient
Atoms
Subscripts
What are the parts to a chemical formula?
Coefficient ~ Tells the number of units of compound. It always goes on the front.
Subscripts ~
Element
Compound
What are the parts to a chemical formula?
Coefficient ~ Tells the number of units of the compound. It always goes in the front.
Subscripts ~ Tells the number of atoms in the compound. Subscript means “below writing”.
Element ~
Compound
What are the parts to a chemical formula?
Coefficient ~ Tells the number of units of substance.
Subscripts ~ Tells the number of atoms in the compound
Element ~ Tells the type of atom in the compound
Compound
What are the parts to a chemical formula?
Coefficient ~ Tells the number of units of substance.
Subscripts ~ Tells the number of atoms in the compound
Element ~ Tells the type of atom in the compound
Compound ~ Tells what combination of atoms, chemically combined, you are looking at.
What are the parts to a chemical formula?
Coefficient ~ Tells the number of units of substance.
Subscripts ~ Tells the number of atoms in the compound
Element ~ Tells the type of atom in the compound
Compound ~ Tells what combination of atoms, chemically combined, you are looking at.
What are the parts to a chemical formula?
Coefficient ~ Tells the number of units of substance.
Subscripts ~ Tells the number of atoms in the compound
Element ~ Tells the type of atom in the compound
Compound ~ Tells what combination of atoms, chemically combined, you are looking at.
C8H10N4O2
This is a compound
What are the parts to a chemical formula?
Coefficient ~ Tells the number of units of substance.
Subscripts ~ Tells the number of atoms in the compound
Element ~ Tells the type of atom in the compound
Compound ~ Tells what combination of atoms, chemically combinded, you are looking at.
C8H10N4O2
This is a subscript
What are the parts to a chemical formula?
Coefficient ~ Tells the number of units of substance.
Subscripts ~ Tells the number of atoms in the compound
Element ~ Tells the type of atom in the compound
Compound ~ Tells what combination of atoms, chemically combined, you are looking at.
C8H10N4O2
This is an element
What do they tell us? They tell us how different chemicals will combine with each other.
What do they tell us? They tell us how different chemicals will combine with each other.
O2 + H2 H2O + heat
What is very, very wrong with this equation?
What do they tell us? They tell us how different chemicals will combine with each other.
O2 + H2 H2O + heat
It is NOT balanced.
Oxygen 2 1
Hydrogen 2 2
What do they tell us? They tell us how different chemicals will combine with each other.
O2 + H2 H2O + heat
O2 + 2H2 ---> 2H2O + heat
Oxygen 2 2
------------------------------------------------------------
Hydrogen 4 4
(Always multiply the coefficient and the subscript)
Some important things to remember.
1. The stuff on the left is the reactants
2. The stuff on the right is the products
3. The total amount of stuff on the left MUST equal the amount of stuff on the right, because of the law of conservation of mass.
Some important things to remember.
1. The stuff on the left is the reactants
2. The stuff on the right is the products
3. The total amount of stuff on the left MUST equal the amount of stuff on the right, because of the law of conservation of mass.
4 g of Hydrogen + 32 g Oxygen = 36 g Water
O2 + 2H2 ---> 2H2O + heat
Balancing equations
1. Solid magnesium burns with gaseous oxygen to make solid magnesium oxide.
2. Step one is to write out the sentence with chemical symbols, according to what actually happens.
Mg (s) + O2(g) --> MgO(s) + energy
Step two is to choose coefficients that balance the number of atoms on each side, but never, never ever change the subscripts. If you change the subsript, you are saying that something else is being made.
2Mg (s) + O2 (g) --> 2MgO(s)
If there is no coefficient, or subscript, it is a “one”.
Hydrogen gas burns with oxygen to make liquid water, and excess energy. Hydrogen gas and oxygen gas are always O2 and H2.
Hydrogen gas burns with oxygen to make liquid water, and excess energy. Hydrogen gas and oxygen gas are always O2 and H2.
H2(g) + O2(g) ---> H2O(l) + energy
Hydrogen peroxide (H2O2) liquid decomposes into oxygen gas and water, if energy is added to the equation.
Hydrogen peroxide (H2O2) liquid decomposes into oxygen gas and water, if energy is added to the equation.
H2O2 + energy --> H2O + O2
Hydrogen peroxide (H2O2) liquid decomposes into oxygen gas and water, if energy is added to the equation.
H2O2 + energy --> H2O + O2
2H2O2 + energy --> 2H2O + O2
Butane gas (C3H8) burns with oxygen gas to make carbon dioxide gas and liquid water, and gives off energy.
Butane gas (C3H8) burns with oxygen gas to make carbon dioxide gas and liquid water, and gives off energy.
C3H8 + O2 ---> CO2 + H2O + energy
Butane gas (C3H8) burns with oxygen gas to make carbon dioxide gas and liquid water, and gives off energy.
C3H8 + 5O2 ---> 3CO2 + 4H2O + energy
Photosynthesis is when sugar, C6H12O6 and O2 combine to make carbon dioxide and water.
C6H12O6 + O2--> CO2 + H2O
Photosynthesis is when sugar, C6H12O6 and O2 combine to make carbon dioxide and water.
C6H12O6 + 6O2--> 6CO2 + 6H2O