Describing Chemical Reactions

1
Describing Chemical Reactions

• Chapter 6.2
• Page 224

2
Section 2Describing Chemical Reactions

• What information does a chemical equation
  contain?
• How is matter conserved during a chemical
  reaction?
• What must a balanced chemical equation show?
• What are three types of chemical reactions?

3
Chemical Formulas

• The chemical formula of a compound identifies the
  elements in the compound and the ratios in which
  their atoms are present.
• What do the following chemical formulas tell you?

4
What Are Chemical Equations?

• Chemical equations use chemical formulas and
  other symbols instead of words to summarize a
  reaction.

5
Conservation of Matter

• The principle of conservation of matter states
  that in a chemical reaction, the total mass of
  the reactants must equal the total mass of the
  products.

6
Conservation of Matter

• In chemical reactions, the number of atoms stays
  the same. They are just rearranged to form
  different substances.
• 6H2O 6CO2 C6H12O6 6O2
• water carbon dioxide
  glucose oxygen

PHOTOSYNTHESIS
7
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.

8
Balancing Equations Activity

• Click the Active Art button to open a browser
  window and access Active Art about balancing
  equations.

9
Balancing Chemical Equations

• Magnesium (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.

10
Balancing Chemical Equations

• Balancing Chemical Equations
• Balance the equation for the reaction of sodium
  metal (Na) with oxygen gas (O2), forming sodium
  oxide (Na2O).

11
Balancing Chemical Equations

• Balancing Chemical Equations
• Balance the equation for the reaction of tin (Sn)
  with chlorine gas (Cl2), forming tin chloride
  (SnCl2).

12
Classifying Chemical Reactions

• Many chemical reactions can be classified in one
  of three categories synthesis, decomposition, or
  replacement.

Synthesis combining two or more substances to
make a more complex substance
Decomposition breaking compounds down into
simpler substances
Replacement when one element replaces another
in a compound
13
End of SectionDescribing Chemical
ReactionsWork on Cornell Notes for 6.2