1. Chemical Reactions Chapter 10 (page 294)

2. Essential Question!!
Why is learning how to identify & classify chemical reactions and writing equations essential to chemist??

3. Vocabulary: Section 1 Chemical reaction Chemical equation Reactants
Products
Law of conservation of mass
Unbalanced chemical equation
Balanced chemical equation

4. The alphabet of chemistry
More than 200,000 words in the English language
Trillions of substances
that make up the universe

5. The language of chemistry
Element symbols
H, O, Na, Fe
Compound formulas
H2O, CO2, NaCl
Chemical equations
2H2 + O H2O
Alphabet
of chemistry
Words
Sentences

6. Chemical Reactions
A chemical reaction is the process of breaking of chemical bonds in one or more substances, and the reforming of new bonds to create new substances.
When you make pizza, which changes are physical and which are chemical changes?

7. Evidence of chemical change
Four indicators of chemical change are:
Formation of new gas
Formation of new solid
Release of energy (heat or light)
Color change

8. Products and reactants
In chemical reactions, you start with reactants that are combined to make products.
The reactants are the starting substances.
The products are the new substances which result from the chemical reaction.

10. Reactants and products
In the reaction, methane (a natural gas) is burned or combusted.
Some energy is added to get the reaction started.

11. Chemical Equations
In a chemical reaction there is always the material you start with and the material you finish with
The starting materials in a reaction are called the reactants
The material you end up with is called the product
Reactants ----- Products

12. Assignment Take a new sheet of paper and fold it into three sections
Write your name, the title of the chapter and the number
On the first section from the sheet of paper, please write six things that you learned from your notes so far that could appear on your test.

13. Chemical Equations
When a chemical reaction is written using chemical formulas and symbols, it is called a chemical equation.

14. Water is: 2H2 + O2 --- 2H2O

15. Chemical Equations-is a way to describe a chemical reaction using chemical formulas and symbols
Antoine Laurent Lavoisier, established an important principal based on his experiments with chemical reactions.
He stated that the total mass of the products of a reaction is equal to the total mass of the reactants.
The law of conservation of mass holds true for even a burning mass of wood.

16. Reactants and products
In the reaction, methane (a natural gas) is burned or combusted.
Some energy is added to get the reaction started.

17. Reaction that fuels the space shuttle:
Hydrogen burns with oxygen to produce water
The “white smoke” is actually water vapor

18. Chemical equations
An arrow is always included between reactants and products.
It means “to produce” or “to yield.”
to produce
Reactants
Products
“Methane combines with oxygen gas to produce carbon dioxide gas and water vapor.”

19. Assignment
Write a three dollar page summary of what was learned this lesson in your journal using 4 of the vocabulary words
Complete page 322 # 1- 6
Honors Chemistry Homework
Page 323 #

20. Vocabulary: Section 2
Balanced chemical equation
Products
reactants

21. Cellular respiration
What is the number of C, H and O atoms on each side of the reaction arrow?

22. Balancing Equations
The combined mass of the burning wood and oxygen is converted into carbon dioxide and water.

23. Conservation of mass
Lavoisier showed that a closed system must be used when studying chemical reactions.
When chemicals are reacted in a closed container, you can show that the mass before and after the reaction is the same.

24. 6 1 8 3 12 2 Not balanced! Cellular respiration Reactants Products
Carbon (C) 6 1
Oxygen (O) 8 3
Hydrogen (H) 12 2
Not balanced!

25. Formula mass
The sum of the atomic mass values of the atoms in a chemical formula is called the formula mass.

26. Molar Mass
The mass (in grams) of one mole of a compound is called its molar mass.

27. Solving Problems What is the molar mass of one mole of CaCO3?
Looking for:
… molar mass of CaCO3
Given
… chemical formula
Relationships:
no. amu in formula = molar mass in grams

28. Formula mass CaC03 = 100.19 g 1 mole CaC03 = 100.19 g CaCO3
Solving Problems
Solution
Formula mass CaC03 = g
1 mole CaC03 = g CaCO3

29. Numbers in equations

30. Balancing equations
The law conservation of mass is applied by balancing the number and type of atoms on either side of the equation.

31. Balancing equations
Counting atoms is necessary to balance an equation.
How many carbon atoms?
How many hydrogen atoms?
How many oxygen atoms?

32. Assignment
On the second section of that sheet of paper, please write six things that you learned from your notes so far that could appear on your test.

33. Strategy to balance a chemical equation:
Write down the unbalanced chemical equation.
Identify the element that occurs in only one compound on both sides, and balance it first.
Continue with the rest of the elements. If a free element is present, it is balanced last.
Check each element to make sure that the equation is balanced.
Make sure the coefficients are the smallest possible whole numbers.

34. Steps for balancing
If not provided, write the word form of the equation.
Calcium carbonate reacts with hydrochloric acid to produce calcium chloride, carbon dioxide and water.

35. Steps for balancing
If not provided, write the chemical equation from the word form.

36. Steps for balancing
Count the number of each type of atom on both sides.

37. Steps for balancing
Add coefficients to balance the equation.

38. Solving Problems
In this reaction, chalcocite (a mineral) reacts with oxygen in the presence of heat. The products are a type of copper oxide and sulfur dioxide. Balance this equation:
Cu2S + O2 → Cu2O + SO2

39. Solving Problems Looking for: Given
…the coefficients for each molecule
Given
… chemical formulas which show types and no. of atoms

40. Solving Problems Relationships
Coefficients can be added in front of any chemical formula in a chemical equation.
When a coefficient is added in front of a chemical formula, all atoms in that formula are multiplied by that number.
Use common denominators to help choose coefficients to try.

41. Solving Problems
Solution- Trial and error

42. Assignment
Write a three dollar summary of what was learned this lesson in your journal using 4 of the vocabulary words
Complete page 322 # 7-14
Honors Chemistry Homework
Page 324 #

43. Vocabulary: Section 3 Decomposition reaction Enthalpy
Single displacement
Double displacement
Precipitate
Solubility
Polymerization reactions
Polymer
Exothermic reaction
Endothermic reaction
Enthalpy
Thermochemical equation
Enthalpy of formation
Photosynthesis
Energy barrier
Spontaneous reaction
Chemical engineering
Green chemistry

44. Chemical equations tell stories…
Reactants Products
… and stories can be put into different categories
Nonfiction
Science fiction
Adventure
Romance
History
Psychology
Children’s literature …

45. Addition reactions
The process of creating large molecules from small ones is called polymerization.

46. Addition reactions
In an addition reaction, two or more substances combine to form a new compound.

47. Decomposition reactions
A chemical reaction in which a single compound is broken down to produce two or more smaller compounds is called a decomposition reaction.

48. Single Displacement
In a single-displacement reaction, one element replaces a similar element in a compound.

49. Double Displacement
In a double-displacement reaction, ions from two compounds in solution exchange places to produce two new compounds.
One of the compounds formed is usually a precipitate that settles out of the solution, a gas that bubbles out of the solution, or a molecular compound such as water.

50. Precipitation reactions
A precipitate is a new solid product that comes out of solution in a chemical reaction.
The formation of a cloudy precipitate is evidence that a double-displacement reaction has occurred.

51. Precipitation
The limewater test for carbon dioxide is a precipitation reaction.

52. Precipitate reaction
Solubility rules for common ionic compounds in water

53. Combustion reactions
A combustion reaction, also called burning, occurs when a substance such as wood, natural gas, or propane combines with oxygen and releases a large amount of energy in the form of light and heat.

54. Combustion reactions
What do reactants like wood, natural gas, and propane have in common?

56. Assignment
On the third section of that sheet of paper, please write six things that you learned from your notes so far that could appear on your test.

57. Oxidation and Reduction
Oxidation is the loss of electrons
Reduction is the gain of electrons
Stronger nonmetals are reduced and weaker nonmetals become oxidized
Generally:
Metals become oxidized
Nonmetals become reduced

58. Objectives Students will be able to:
Contrast endergonic and exergonic reactions.
Contrast endothermic and exothermic reactions.
Explain why activation energy is needed to begin chemical reactions.
Describe what happens when ionic compounds are dissolved in water.

59. Energy and Reactions
Energy is involved in chemical reactions in two ways:
to break some (or all) bonds between atoms in the reactants so the atoms can form new bonds or
when the atoms or products form new bonds to make new products.

60. Two Types of Reactions
We classify chemical reactions based on how the energy of the reactants compares to the energy of the products.

61. Exothermic reactions
If forming new bonds releases more energy than it takes to break the old bonds, the reaction is exothermic.

62. Exothermic reactions
A good example is the reaction of hydrogen with oxygen.
Once started, exothermic reactions tend to keep going as each reaction releases more energy to fuel neighboring molecules.

63. Endothermic reactions
If forming new bonds in the products releases less energy than it took to break the original bonds, the reaction is endothermic.

64. Endothermic reactions
An important endothermic reaction is photosynthesis.
Plants need energy from sunlight to make glucose and oxygen from carbon dioxide and water.

65. Activation Energy
Activation energy is the energy needed to begin a reaction and break chemical bonds in the reactants.

66. Activation Energy
This is why a flammable material like gasoline does not burn without a spark or flame.

67. Carbon Reactions
Carbon dioxide and other atmospheric gases are called “greenhouse gases.”
Scientists believe the rise in amount of greenhouse gases will result in rises in sea level and changes in weather.

68. Assignment
On the first section of the back side of that sheet of paper, please write six things that you learned from your notes so far that could appear on your test.

69. Examples of Endothermic Reactions
Most of the reactions used in industry to produce useful materials require more energy than they produce.
One process that uses endothermic reactions is the refining of ores to produce useful metals.

70. Examples of Endothermic Reactions
Most of the reactions used in industry to produce useful materials require more energy than they produce.
The reaction taking place inside an instant cold pack is endothermic.

71. Catalyst and Inhibitors
A catalyst is a substance that speeds up a chemical reaction without being permanently changed in the process
Inhibitors are substances that are used to slow down a chemical reaction

72. Examples of Endothermic Reactions
When you squeeze the plastic bag the water reacts with the ammonium nitrate crystals, and the reaction dissolves the ionic bonds in the ammonium nitrate.

73. Examples of Endothermic Reactions
The reaction is also a dissolution reaction.
Dissolution occurs when an ionic compound (like ammonium nitrate) dissolves in water to make an ionic solution.

74. Assignment
Write a three dollar summary of what was learned this lesson in your journal using 4 of the vocabulary words
Complete page 322 # 15-23
Honors Chemistry Homework
Page 325 #

75. Test: - Next week Tuesday or Thursday depending on your block
Homework requirement: Learn all terms and concepts learned on this topic
Make sure you have all assignments between page completed and turned in by your test date.