1. Describing Chemical Reactions
Chapter 6.2
Page 224

2. Section 2: Describing 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 + 6CO C6H12O O2
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
Balance the equation for the reaction of sodium metal (Na) with oxygen gas (O2), forming sodium oxide (Na2O).

11. 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 Section: Describing Chemical Reactions Work on Cornell Notes for 6.2