Objectives To learn the signals or evidences that show a chemical reaction may have occurred

Whoosh Can You Identify any Evidences of a Chemical Reaction?

To learn to identify the characteristics of a chemical reaction Objectives To learn to identify the characteristics of a chemical reaction To learn the information given by a chemical equation

Physical states of compounds are often given in a chemical equation.

Chemical reactions involve a rearrangement of the ways atoms are grouped together. A chemical equation represents a chemical reaction. Reactants are shown to the left of an arrow. Products are shown to the right of the arrow.

The Law of Conservation of Mass The Law of Conservation of Mass states that mass is neither created nor destroyed during a chemical reaction. Plop, Plop, Fizz, Fizz….. A chemical reaction involves the rearrangement of atoms to form new substances. (Coins)

In a chemical reaction atoms are not created or destroyed. All atoms present in the reactants must be accounted for in the products. (Video Clip) (Magnets) Same number of each type atom on both sides of arrow ___CH4 ___O2 ___CO2 ___H2O

In a chemical reaction atoms are not created or destroyed. All atoms present in the reactants must be accounted for in the products. (Video Clip) (Magnets) Same number of each type atom on both sides of arrow ___CH4 ___O2 ___CO2 ___H2O

To learn to identify the characteristics of a chemical reaction Objectives Review To learn the signals or evidences that show a chemical reaction may have occurred To learn to identify the characteristics of a chemical reaction To learn the information given by a chemical equation Work Session: page 234 1, 5, 6, 7, 8 Video of Various Chemical Rx’s Ch 7(Silver I)

To learn to write a balanced equation for a chemical reaction Objectives To learn to write a balanced equation for a chemical reaction Are you ready??

C2H5OH + 3O2  2CO2 + 3H2O A representation of a chemical reaction: reactants products Reactants are only placed on the left side of the arrow, products are only placed on the right side of the arrow. The equation is balanced because all atoms present in the reactants are accounted for in the products. The balanced equation represents an overall ratio of reactants and products, not what actually “happens” during a reaction.

Atoms (mass) are always conserved Can only change the coefficients A chemical reaction is balanced by using a systematic approach: Atoms (mass) are always conserved Can only change the coefficients Balance by trial and error starting with the most complicated molecule(s) At the end check to be sure the equation is balanced (same numbers of all types of atoms on the reactant and product sides)

Example:  Hydrogen gas and oxygen gas combine to form liquid water. Write the formulas of the reactants and products to give the unbalanced chemical equation. ___H2(g) + ___O2(g)  ___H2O(l)

Use a pencil and don’t be afraid of erasing! A chemical reaction is balanced by using a systematic approach: (Patch’s Interpretation) Make Sure you have the equation written correctly and leave spaces in front of each compound formula. Use a pencil and don’t be afraid of erasing! Make sure you are NOT violating the Law of Conservation of Mass!!

___K + ___H2O  ___H2 + ___KOH ___CH4 + ___O2  ___ CO2 + ___H2O More Examples: ___N2 + ___H2  ___ NH3 ___O2  ___ O3 ___K + ___H2O  ___H2 + ___KOH ___CH4 + ___O2  ___ CO2 + ___H2O ___C2H5OH + ___O2  ___ CO2 + ___H2O ___C3H8 + ___O2  ___ CO2 + ___H2O ___HF + ___SiO2  ___ SiF4 + ___H2O ___NH3 + ___O2  ___ NO + ___H2O

___HNO3  ___NO2 + ___ H2O + ___O2 Independent practice: ___NH4NO2  ___N2 + ___H2O ___NO  ___ N2O + ___NO2 ___HNO3  ___NO2 + ___ H2O + ___O2

I. The number of molecules is conserved. Concept Check Which of the following are true concerning balanced chemical equations? There may be more than one true statement. I. The number of molecules is conserved. II. The coefficients tell you how much of each substance you have. III. Atoms are neither created nor destroyed. IV. The coefficients indicate the mass ratios of the substances used. V. The sum of the coefficients on the reactant side equals the sum of the coefficients on the product side. Only III is correct.

Let’s use all of your skills to write a reaction equation to describe the following: Solid Carbon reacts with gaseous oxygen to form gaseous carbon dioxide. Solid Mercury (II) oxide decomposes to produce elemental mercury metal and gaseous oxygen. Solid zinc is added to an aqueous solution of hydrogen chloride to produce gaseous hydrogen that bubbles out of the solution and zinc chloride that remains dissolved in the water.

To learn to write a balanced equation for a chemical reaction Objectives Review To learn to write a balanced equation for a chemical reaction Work Session: page 234: 31, 32, 33, 34, 35, 36 Page 237: 1-8

This is the end of the required material for this chapter.

Example:  Hydrogen gas and oxygen gas combine to form liquid water. Balance by trial and error starting with the most complicated molecule(s).

Example:  Hydrogen gas and oxygen gas combine to form liquid water. At the end check to be sure the equation is balanced (same numbers of all types of atoms on the reactant and product sides). 2H2(g) + O2(g)  2H2O(l)

Balancing a Chemical Equation Unbalanced equation Balancing the equation The balanced equation CH4 + 2O2  CO2 + 2H2O