Chapter 6
Evidence Chemical Reaction
- Will give a visual signal usually
o Colour change
o Solid forms
o Bubbles form
o Heat or flame form
- But reactions are not always visible
Evidence for a chemical Reaction
- Reactant -> Product
- Involve a rearrangement of the way atoms are
grouped together
- We do not want to alter the atom itself but just to
balance the equation
o Try to balance the most complex first and then
go from there
- A chemical equation represents a chemical reaction
*All atoms presented are not created or destroyed*
How to write and Balance Equation
1. Read the description of the chemical reaction, what are the reactants, the product
and the state?
a. E.g. Hydrogen gas – H2
b. E.g. Oxygen gas – O2
c. E.g. Water – H2O
2. Write the unbalance equation that summarizes the information from step 1
a. H2 (g) + O2 (g) -> H2O (l)
3. Balance the equation (start with the most complicate molecule)
a. 2H2 (g) + O2 (g) -> 2H2O (l)
4. Check to see that the coefficients used give the same number of each type of atom
on both sides of the arrow; also, the coefficients used the smallest integers that give
the balanced equation
Summary:
- The number of atoms of each type of element must be the same on both sides of a
balanced equation
Evidence Chemical Reaction
- Will give a visual signal usually
o Colour change
o Solid forms
o Bubbles form
o Heat or flame form
- But reactions are not always visible
Evidence for a chemical Reaction
- Reactant -> Product
- Involve a rearrangement of the way atoms are
grouped together
- We do not want to alter the atom itself but just to
balance the equation
o Try to balance the most complex first and then
go from there
- A chemical equation represents a chemical reaction
*All atoms presented are not created or destroyed*
How to write and Balance Equation
1. Read the description of the chemical reaction, what are the reactants, the product
and the state?
a. E.g. Hydrogen gas – H2
b. E.g. Oxygen gas – O2
c. E.g. Water – H2O
2. Write the unbalance equation that summarizes the information from step 1
a. H2 (g) + O2 (g) -> H2O (l)
3. Balance the equation (start with the most complicate molecule)
a. 2H2 (g) + O2 (g) -> 2H2O (l)
4. Check to see that the coefficients used give the same number of each type of atom
on both sides of the arrow; also, the coefficients used the smallest integers that give
the balanced equation
Summary:
- The number of atoms of each type of element must be the same on both sides of a
balanced equation
