1. Unit 2- Materials: Structure and Uses

2. Unit 2- Materials: Structure and Uses
Section 2. A –
Why we use what we do

3. Do Now
Read pages

4. Objectives 1. Define properties and changes.
2. Distinguish between physical and chemical changes and classify examples of each.
3. Differentiate between metals, non metals, and metalloids and their locations on the period table.
4. Distinguish between isotopes based on total neutrons.

5. Unit 2. A.1-A3: Reading Guide
Complete the reading guide worksheet
Due:

6. 2.A.1: Properties make the difference
What are some materials people of the past have used as currency?
What makes a material suitable or useable to produce coins?
How important is appearance or cost?
Answers depend on physical and
chemical properties

7. Physical Properties
Characteristics that distinguish elements from other things
Ex. Color, density, odor…
Can be observed without altering chemical structure

8. Physical Properties
Physical properties and the ability of a material to undergo physical changes, such as melting, boiling and bending, influence the use of that material.
In a physical change, the material remains the same, although it form appears to have changed.

9. Chemical Property
Describes how the element reacts with other elements or substances.
When a substance changes into one or more new substances, it has undergone a chemical change.
A substance’s chemical properties, often determine the substance’s usefulness.

10. Chemical Property
Chemical change is often observed such as: formation of a gas or solid, a permanent color change or a temperature change.

11. Physical vs. Chemical Property
Copper
metal
Physical
Chemical

12. Chemical vs. Physical Changes
Chemical Change
Physical Change
-substance changes into one or more NEW substances
-Appearance can change although chemical structure remains intact

13. Example
Iron RUSTING:
Observing a chemical change can often mean the formation of a gas or solid
Thermal energy can be given off or absorbed
Permanent color change
Temperature change

14. 2.A.2: Physical and
Chemical Properties

15. Objectives
Distinguish between physical and chemical changes and classify examples of each.

16. Problem 1: p.111
Consider the statement: Copper compounds are often blue in color. Does this statement describe a physical or chemical property? Why?

17. Answer
Consider the statement: Copper compounds are often blue in color. Does this statement describe a physical or chemical property?
Color is a characteristic physical property of many compounds

18. Problem 2: p. 111
Consider this statement: Oxygen gas supports the burning of wood. Does this statement refer to the physical or chemical property of oxygen gas? Explain.

19. Answer Burning or combustion of wood- involves a chemical reaction
Wood and oxygen (reactants) change into ash, carbon dioxide and water vapor.

20. Do Now
List at least one chemical property and one physical property

21. Homework
Page 112: Questions #1-9
Due:

22. Unit 2. A1
Quiz – complete A.1 supplement
worksheet

23. A.3: Properties Matter Considerations when selecting materials
for a specific use:
Cost
Desired properties (physical and chemical)
Available in sufficient quantities

24. A.3: Properties Matter: Designing the Penny
1. Cost
A. Cost of the production of the penny must be matched by it’s face value ($0.01)
B. Early 1980s Copper became too expensive and Zinc replaced it in most of the penny (interior)
C. In 1943, during WWII, Zinc plated steel pennies (quickly corroded)

26. A.3: Properties Matter: Designing the Penny
2. Solution
Post 1982 pennies – 97.5% Zinc
Copper coating a Zinc Core

27. A.4: Chemical Elements

28. Objectives
Identify properties of metals, nonmetals, or metalloids

29. A.4: Chemical Elements Elements are classified in three major groups:
Metals
Nonmetals
Metalloids
Use the periodic table to distinguish the classes of elements

30. Periodic Trends

31. Transition Metals
Transition metals

32. Physical Properties of Metals
Malleability
Ductility
Luster
Heat conductors and electrical conductors
Typically reacts with acids
Ex. Iron (Fe), tin (Sn), zinc (Zn), and copper (Cu)

33. Properties of Nonmetals
Dull in appearance
Brittle
Do not conduct electricity
Ex. Carbon (C) and Oxygen (O)

34. Metalloids Properties of metals and nonmetals
Ex. Silicon (Si) and Germanium (Ge)
Common in the computer
industry

35. Class Project
A.4 Supplement handout
Due:

36. Do Now List the following as a chemical or physical change:
1. A piece of wood burns to form ash.
2. Water evaporates into steam.
3. A piece of cork is cut in half.
4. A bicycle chain rusts.
5. Food is digested in the stomach.
6. Water is absorbed by a paper towel.
7. A change in color

37. A.5: Metal or Nonmetal
Lab
Handout

38. Periodic Trends

41. A.6: Periodic Table Objectives 1. Review physical and chemical changes
2. Identify trends in the periodic table.

42. Periodic Table
By the mid-1800’s, chemists has identified about 60 elements
Five were gases: hydrogen, oxygen, nitrogen, fluorine and chlorine
Two liquids: bromine and mercury
The rest were solids

43. A.6: Periodic Table
Used to organize elements based on their similar properties

44. Dimitri Mendeleev
Created a periodic table (1869) of elements based on:
1. Atomic Weights
2. “Combining Capacity” (how atoms react with other atoms.

45. Periodic Table
Elements with similar chemical properties were placed in the same vertical column.
Horizontal arrangements were based on increasing atomic weights of the elements.

46. A.7: Grouping the Elements
Now you Try
Turn to page 119 and follow steps #1-6
Try to create your own periodic table based on several different properties

47. A.8: The Pattern of Atomic Numbers
Creators of early periodic tables were unable to explain the similarities in properties among neighboring elements.
All elements in the leftmost column are very reactive metals.
All elements in the rightmost column are unreactive (noble) gases.
50 years after Mendeleev for explanation.

48. A.8:
All atoms are composed of smaller particles, including equal numbers of positively charged protons and negatively charged electrons.

49. Atomic Number – the number of protons
Identifies each atom as a particular element.
Each element has its own unique atomic number.
Example: each sodium atom contains 11 protons. Atomic number of sodium is 11

50. The carbon atom contains 6 protons. Atomic number of sodium is 6
The fluorine atom has 9 protons and an atomic number of 9
Magnesium has 12 protons and an atomic number of 12

51. Refer to the periodic table to identify the elements and atomic numbers (number of protons).
The modern periodic table is arranged by placing the elements in increasing atomic number.

52. In electrically neutral atoms (no charge) the number of positively charged protons equals the number of negatively charged electrons.
Each sodium atom contains 11 protons and 11 electrons.
Each carbon atom contains 6 protons and 6 electrons.

53. Atomic Weight – the total mass of an atom.
Atomic weight is equal to the mass of protons plus the mass of neutrons.
Neutron – an small uncharged particle found in the nucleus of the atom.
Nucleus – the center of the atom containing the protons and neutrons.

54. Mass Number– equal to the total number of protons plus the total number of neutrons.
Generally, the atomic weight of an atom equals its mass number.
Remember that mass number and atomic number are not the same.

56. Isotopes
While all atoms of a particular element have the same number of protons, the number of neutrons can differ from atom to atom of an element.
Carbon: always has 6 protons, but it may contain either 6, 7 or 8 neutrons.
Therefore, carbon may have a mass number of 12, 13 or 14.

57. Isotopes For example, 6 protons + 6 neutrons = mass number of 12

58. Isotopes
Atoms with the same number of protons but different number of neutrons are called isotopes.
Isotopes are atoms of the same element with different mass numbers.
Carbon has 3 isotopes with a mass number of 12, 13 or 14.

59. A.8: Atomic Numbers
Homework: A.8 supplement worksheet
Due:

60. A.10: Organization of the Periodic Table
Refer to periodic table on page 124

61. Periodic Trends Periods: horizontal rows
Groups/Families: vertical columns

62. Periods: horizontal rows
The atomic number (number of protons) increase from left to right across a row.
Elements on the left side are chemically different than elements on the right side of a row (sodium and chlorine).

63. Groups/Families: vertical columns
Each vertical column contains elements with similar properties (sodium, potassium and cesium).
Each vertical column is given a name based on these similar properties.

64. Trends in Periodic Families
Alkali Metal Family:
Group 1
Highly reactive Metals (sodium)
Noble Gas Family:
Group 18
Unreactive (chemically inert) elements (argon)
Halogen Family:
Group 17
Highly reactive (fluorine, chlorine)

66. A.11: Predicting Properties
Some element properties can be estimated by averaging the respective properties of the elements located just above and just below an element on the periodic table.
Mendeleev was able to predict the properties of many unknown elements using this method.

67. Sample problem 1
Given that the density of silicon (Si) is 2.3 g/cm3 and the density of tin (Sn) is 7.3 g/cm3, estimate the density of germanium (Ge).

68. Answer sample problem 1
Density of silicon (Si) is 2.3 g/cm3 and the density of tin (Sn) is 7.3 g/cm3
All three elements are in the same group on the periodic table. Germanium is below silicon and above tin. Therefore the predicted density of germanium is 4.8 g/cm3, the average of silicon and tin densities (actual density is 5.3 g/cm3)

69. Sample problem 2
Formulas for chemical compounds can also be predicted using the periodic table.
For example carbon (C) and oxygen (O) form carbon dioxide (CO2).
Predict the formula for the combination of carbon (C) and sulfur (S)?

70. Answer sample problem 2
Carbon (C) and oxygen (O) form carbon dioxide (CO2).
The periodic table indicates sulfur and oxygen are in the same family (column).
Therefore the predicted formula would be CS2 – carbon disulfide

71. Classwork
Page 126 in text book
Questions 1 – 4
Due:

72. Homework
Unit 2, A.11 supplement handout
Predicting properties
Due:

73. A.12: What Determines Properties
Number of protons (atomic number) determines the identity of the element.
Number and arrangement of electrons determine many chemical properties.
Interatomic attraction determines physical properties such as melting and boiling points.

74. A major difference between metals and nonmetals is that metals lose electrons while nonmetals gain electrons.
If a metal loses electrons it becomes a positively charged cation.
If a nonmetal gains electrons it becomes a negatively charged anion.

75. Some physical properties of metals depend on the attractions among their atoms.
Stronger attractions result in higher melting and boiling points.
Magnesium has a melting point of 650 oC and sodium has a melting point of 98 oC.
Attraction of atoms is higher for magnesium than sodium.

76. Chemical and physical properties of nonmetals also depend on the attractions among their atoms.
The very high boiling and melting point of water (Unit 1) is due to the attraction of the hydrogen and oxygen atoms (positive and negative attraction).

77. Understanding the properties of atoms is the key to predicting the behavior of materials.
These properties explain the physical and chemical world around us.

78. A.13: Desired Properties of Coins
What physical properties must a coin have?
High melting point and identifiable color
What physical properties are desirable?
Size, shape and luster

79. What chemical properties must a coin have?
Resistance to corrosion and reactivity with other metals

80. What would make the best material for a new coin: a metal, nonmetal or metalloid?
Metals have the appropriate physical and chemical properties required.
Nonmetals and metalloids do not.

81. Homework
Unit 2, Section A supplement handout