2.B: Earth’s Mineral Resources

Objectives

1) Describe the chemicals in the Earth’s atmosphere, hydrosphere and lithosphere.

2) Describe and recognize factors that determine the feasibility of mining.

3) Define oxidation and reduction. 4) Identify oxidation and reduction

processes.

2.B.1: Sources and Uses of Metals

1) Human needs for resources must be met by chemical supplies currently present on Earth.

2) The needs include: creating a new coin, manufacturing of clothing, petroleum products, fertilizer for food and energy needs.

3) Resources can be cataloged by where they are found on Earth.

2.B: Earth’s Mineral Resources

Atmosphere: provides nitrogen, oxygen, neon and argon.

Hydrosphere: water and dissolved minerals.

Lithosphere: solid part of the earth which provides the greatest variety of chemical resources. These include petroleum, metals, ores and minerals.

Earth’s Resources

Earth’s Resources

Ore: a naturally occurring rock or mineral that can be mined.

An ore contains a mixture of components.

Of these minerals are the most important part of the ore.

Average thickness is 3,840 miles. Most of the mined resources occur in the first 25 miles (crust).

Metals found in the crust include: aluminum, sodium, iron, calcium, magnesium and potassium.

These metals must be mined form the earth.

Lithosphere

Challenges faced in mining:

1. Use of supplies needed to mine the metal2. Where should mining occur3. The quantity of useful ore found at the site4. The percent of metal in the ore5. The type of mining and processing needed to

extract the metal from its ore6. The distance between the mine and metal-refining

facilities and markets7. The metal’s supply vs. demand status8. The environmental impact of the mining and metal

processing.

Mining Copper Ores

Copper is one of the most familiar and widely used metals in society. Uses include:

1) Electrical wiring.2) Second only to silver in electrical conductivity.3) Relatively low cost and corrosion resistance4) Ductility – ability to be drawn into wires.5) Used to produce brass, bronze, jewelry and

artwork.

Properties of Copper

Mining Copper Ores

The first copper ores mined were relatively rich in copper metal: 35% to 88%.

Such ores are no longer available. Today it is possible to mine ores

containing less than 1% copper These ores are chemically processed

to produce metallic copper.

Classwork

Using the table on page 136, answer the following questions:

1) What metal might Australia wish to obtain from the United States?

2) What metal could Australia export to the United States?

3) From which nation might the United States to obtain nickel?

4) What metal does China have in abundance compared to there nations?

5) What metals might Canada seek to import?

B.2 Production vs. Use

Follow the guidelines on page 138-139 to research the metal you are assigned.

Prepare a PowerPoint presentation answering questions (following slide) about your metal.

Due: Class Presentation – March 25th

PowerPoint Presentation

Cover slide – name of metal / name of student Symbol of metal, number of protons, common

isotopes of the metal Where is metal found on earth (countries) History of metal How abundant is metal (worldwide production) The metals properties (shiny, color soft, etc.) Three current uses of metal

Some useful websites for your research

All metals: http://minerals.usgs.gov/mineralshttp://pearl1.lanl.gov/periodic/default.htm

Aluminum: www.aluminum.org Copper: www.copper.org Lead: www.ldaint.org/default.htm Nickel: www.nickelinstitute.org Silver:

http://www.silverinstitute.org/index.php Tin: http://minerals.usgs.gov/ Zinc: www.zincworld.org

B.3: Converting Copper

Lab: Handout and page 139 in textbook

B.4: Metal Reactivity

2 Cu(s) + O2(g) 2 CuO (s)

a. Identify the reactant(s).

b. Identify the product(s).

c. What do the letters in parentheses represent?

Symbols used in chemical equations:

(s) = solid (l) = liquid, typically H2O, Hg and Br (g) = gas (aq) = aqueous solutions, the solvent

has to be water. Ex. Salt water solution

Although copper metal reacts with oxygen gas when heated, no reaction takes place at room temperature.

This fact is observed with copper pennies or copper wiring that do not turn black under normal conditions.

Magnesium metal also reacts with oxygen gas to form magnesium oxide.

Unlike copper metal, magnesium heated in air ignites and produces a brief flash of light.

Magnesium metal is used in fireworks.

2 Mg(s) + O2(g) 2 MgO (s)

By contrast, gold (Au) does not react with any components in air, including oxygen gas.

This makes gold a valuable metal.

It is ideal to use in jewelry, automobile components and audio cables (gold plated components) because it is non reactive.

Thousands of chemical reactions are known to occur in living systems, industrial process and chemical labs.

But just because you mix two reagents together does not mean they will react.

There is a way to predict whether a reaction will occur.

Activity Series The ranking of elements according to their

chemical reactivity. Table on page 145.

For example, Au (gold), does not react with any components of air such as oxygen. This is one reason why it is used in jewelry. Therefore it is ranked low on the Metal Activity Series.

Elements higher on the list are more reactive.

Elements higher on the list can replace elements below it in a chemical reaction.

Metal Activity Series Reactive metals

are more difficult to release from their compounds.

Ex. Can zinc (Zn)

replace Magnesium in Mg(NO3)2?

Can Zn ever replace copper (Cu) in a chemical reaction?

Please rank the following elements in order of reactivity (based on the activity series chart on page 145). List the most reactive element first.

Gold, copper, chromium, magnesium, potassium

B.5: Relative Reactivities of Metals

Lab: Handout and page 142 in textbook

B.6: Metals

Certain metals in nature are found in the uncombined stated.

These metals are known as free elements, rather than in combination with other elements.

These metals include gold, copper and silver. Because they are not combined with other

elements they were the first metals used by man. These metals are also very unreactive.

Most metals are usually found in the form of a metallic ore (combined with other elements)

Metallic ores are also known as minerals. These metals include aluminum and iron. These metals need to be extracted or separated

from their ores to yield the pure metal. Bronze and brass are a combination of copper with

another metal and not a pure metal. Because these metals need to be extracted from

their ores they were used by humans at a later time.

Metal alloys

• An alloy is a mixture of 2 or more elements (one must be a metal)

• These are uniform throughout, so a homogeneous mixture

• Examples: Brass (copper and zinc); Sterling silver (silver and copper) Bronze (copper and tin)

Why have alloys?• Alloys are important because they are combining

properties and are often superior compared to the pure elements

• Typically, more inexpensive than the pure element:• Sterling silver vs pure silver

$0.95 vs $1.68

B.7: Trends in Metal Activity

Class Assignment

Page 146: Questions 1-3

B.8: Oxidation – Reduction Reactions

B.8: Reading Guide Worksheet

IONS

Atoms are neutral because the protons which are positive and electrons that are negative balance out the charge, so there are the same numbers of protons and electrons in an atom. An ion is an atom or group of atoms that has a positive or negative charge due to loss or gain of electrons. There are two forms of ions: cation and anion.

B.8: Review of Ions

Cation – positive ion

Anion – negative ion

Some cations(metals)

Some anions (non metals)

Na+, Cu+2, Mg+2, Fe+2, Al3+, Zn+2

Cl-1, O-2, N-3, S-2

35

Cu+2 (loss of electrons)

Cl- (gain of electrons)

Cu Cu2+ + 2e-

29 protons (+) 29 protons (+)

29 electrons (-) 27 electrons (-)

Net charge = 0 Net charge = +2 Net charge = -2

B.8: Review of Ions

Overall charge on both sides of the reaction arrow are the same

Oxidation – Reduction Reaction

Most metals are not found free in nature. They are found combined with other elements.

These combined compounds are more stable. Metals in the combined state are cations (M+) Metals in the free state (M)

The process of converting cations to a free metal is an oxidation-reduction reaction.

B.8:Oxidation – Reduction Reaction

Reduction:Gain of electrons by a reactant.Ex.

• Cu2+ + 2e- Cu

• The copper cation was reduced, lost its charge by gaining electrons

Converting copper cation (+2) to copper metal

requires the addition of 2 electrons

Oxidation – Reduction Reaction

Oxidation:Loss of electrons.

Ex.• Fe Fe3+ + 3e-

• Iron is oxidized to an iron (III) ion by losing 3 electrons

Remember…

OIL RIGOIL – Oxidation Is Loss (of electrons)

RIG – Reduction Is Gain (of electrons)

Oxidation – Reduction Reaction

Oxidation and reduction reactions occur together and are called redox reactions.

Oxidation and reduction reactions never occur separately.

Cu2+(aq) + Mg(s) Cu(s) + Mg2+(aq)

- Which reactant (Cu2+or Mg(s)) is reduced?

- Which is oxidized?

Oxidation – Reduction Reaction

In a redox reactions the electrical charge, as well as, the atoms must be balanced on either side of the reaction arrow.

This is known as a balanced equation.

Cu2+(aq) + Mg(s) Cu(s) + Mg2+(aq)

The total electrical charge on both sides of the reaction arrow is +2 in the above equation.

On the activity series chart, magnesium is above copper allowing the reaction to occur.

Oxidation – Reduction Reaction

Classwork: Redox Worksheet (B8)

Using Redox Reactions to obtain Pure Metals

Techniques that are used to reduce metal cations to pure metals in industry include:

Electrometallurgy - use of electric current

Pyrometallurgy – use of heat

Hydrometallurgy – use of water

Electrometallurgy

This technique involves using an electrical current to supply electrons to the metal ions.

This process is used when no other chemical reducing agent is available.

Also allows for the production of very high-purity metals.

Pyrometallurgy

The use of heat (blast furnace) is used.

Carbon or carbon monoxide are the common reducing agents supplying the electrons for the reduction reaction.

The oldest method to obtain pure metals from ores.

Hydrometallurgy

This technique uses water to treat the ores.

Used to recover gold and silver from old mines.

Process is known as leaching.

Oxidation – Reduction Reaction

Homework – reading guide Due: Use as a section review

Homework – B8 Supplement Worksheet Due:

End of Chapter

B.9: Naming Ionic Compounds

New PowerPoint presentation.