Download Chemical Equations

Chemical Reactions
Performance Expectations
• MS-PS1-5. I can explain the conservation of mass through
a model of chemical reactions.
• MS-PS1-3 I can gather information to describe the origins
and impacts of synthetic material
What is a chemical reaction?
• When elements and/or compounds interact to form new
compounds
• A new substance is made during a chemical reaction
Chemical Equations
• We use chemical equations to represent the chemical
reaction with chemical formulas and numbers.
2 H2 + O2  2 H2O
This is the chemical equation showing how hydrogen and
oxygen react to make water
Parts of a Chemical Equation
Reactants and Products
• Chemical reactions are read left to right.
• The starting substances are called the reactants
• The substance that is made as a result of the chemical
reaction are called products
2 H 2 + O 2  2 H2 O
Reactants
Products
Parts of a Chemical Equation
Chemical Formulas
• A chemical formula is a why to represent a substance.
• Atomic Symbols- from the periodic table to represent the
types of atoms in the substance
• Subscripts- tell the number of each type of atom in a
molecule
2 H 2 + O 2  2 H2 O
H2 is the chemical formula
for a hydrogen molecule.
H2O is the chemical
formula for a water
molecule
Parts of a Chemical Equation
Coefficients
• Coefficients tell us the proportions that the molecules need
to react in.
• They show how matter is conserved
2 H2 + O2  2 H2O
The coefficient of 2 shows us
that two molecules of
hydrogen need to react for
every 1 molecule of oxygen
Not having coefficient is the same as
saying 1
How Do I know a Chemical Reaction
Happened
• You may not be able to see the molecules but there are
some signs that a reaction has occurred
• Color Change
• Creation of a New Gas
• Change in Temperature
• Smell
• Light
Vocabulary Pt II.
Chemical formula
A representation of a substance in which the elements are
represented by their symbols and subscripts represent the
number of atoms of each element
H 2O
Chemical change
The formation of a new substance with different properties;
cannot be undone by physical means
Chemical equation
A representation of a chemical reaction by symbols and
numbers
2 H2 + O2  2 H2O
Law of conservation of mass
Matter is not created or destroyed; only rearranged
Product
Substance(s) resulting from a chemical reaction
Reactant
Substances that are combined and changed during a
chemical reaction
Element
A substance made of only one kind of atom.
Synthetic
Made by human means and not originally found in nature.