Transcript Living Things - Holland Public Schools

Chemical Reactions - Describing Chemical Reactions
Describing Chemical Reactions
Cellular phone messages make use of symbols and
abbreviations to express ideas in shorter form. Similarly,
chemists often use chemical equations in place of words.
Chemical Reactions - Describing Chemical Reactions
What Are Chemical Equations?
Chemical equations use chemical formulas and other
symbols instead of words to summarize a reaction.
Chemical Reactions - Describing Chemical Reactions
Chemical Formulas
The formula of a compound identifies
the elements in the compound and the
ratios in which their atoms are present.
Chemical Reactions - Describing Chemical Reactions
Conservation of Mass
The principle of conservation of mass states that in a
chemical reaction, the total mass of the reactants must equal
the total mass of the products.
Chemical Reactions - Describing Chemical Reactions
Balancing Chemical Equations
To describe a reaction accurately, a chemical equation must
show the same number of each type of atom on both sides of
the equation.
Chemical Reactions - Describing Chemical Reactions
Balancing Equations Activity
Click the Active Art button to open a browser window and
access Active Art about balancing equations.
Chemical Reactions - Describing Chemical Reactions
Balancing Chemical Equations
Magnesium metal (Mg) reacts
with oxygen gas (O2), forming
magnesium oxide (MgO). To
write a balanced equation for
this reaction, first write the
equation using the formulas of
the reactants and products, then
count the number of atoms of
each element.
Chemical Reactions - Describing Chemical Reactions
Balancing Chemical Equations
Balancing Chemical Equations:
Balance the equation for the
reaction of sodium metal (Na)
with oxygen gas (O2), forming
sodium oxide (Na2O).
Chemical Reactions - Describing Chemical Reactions
Balancing Chemical Equations
Balancing Chemical Equations:
Balance the equation for the
reaction of tin (Sn) with
chlorine gas (Cl2), forming tin
chloride (SnCl2).
Chemical Reactions - Describing Chemical Reactions
Remember These?
Key Terms:
Examples:
Chemical Formula
A chemical equation is a short, easy way to show a
chemical reaction.
Chemical Equation
conservation of mass
Conservation of mass means that during a chemical
reaction, matter is not created or destroyed.
reactant
A new substance produced in a reaction is a product.
product
arrow
A substance you have at the beginning of a reaction is
a reactant.
subscript
Coefficient
A coefficient is a number in a chemical equation
telling you how many atoms or molecules of a reactant
or product take part in the reaction.