Preliminary Chemistry- Dot Points on MetalsMetals

1. Metals have been extracted and used for many thousands of years.

-Outline and examine some uses of different metals through history, including contemporary uses, as uncombined metals and alloys.

Copper Age (3200 - 2300 BC): Copper was the first metal to be extracted from its ore. Molten copper was used to make ornaments and utensils. Its MP was very high and its products were soft.

Bronze Age (2300 – 1200 BC): Heating copper with tin produces bronze. Bronze was much harder than copper and had a lower MP and was used for making tools and weapons.

Iron Age(1200 BC – 1AD): Iron was more reactive than copper so it required a higher temperature to extract. Hematite (Fe2O3) was mixed with charcoal and heated in a primitive furnace to obtain a high temperature. It replaced bronze for making weapons as it had a higher tensile strength and was harder than bronze.

Modern Age (1 AD – present): The modern age was characterized by the extraction and use of many other metals such as aluminum, chromium, and alloys. Although iron and its alloys are still the most widely used metal today, many other metals have come into common use due to advancements in extraction technology.

-Describe the use of common alloys including steel, brass, and solder and explain how these relate to their properties.

Alloy Properties Uses

Mild Steels

Soft and malleable Car bodies, roofing, pipes, nuts and bolts

Structural Steels

High tensile strength, hard

Beams, girders, railways, concrete reinforcement

Brass Lustrous gold appearance, hard, easily machined

Plumbing, musical instruments, decorations

Bronze Hard, resists corrosion, easily cast

Casting statues, shipping propellers

Solder Low MP, adheres firmly to other metals

Joining metals together

-Explain why energy input is necessary to extract a metal from its ore

In order to break the chemical bonds in the compounds, energy such as heat or electricity is required to break these bonds and extract the metal.

-Identify why there are more metals available for people to use then there were 200 years ago.

Many metals are available because of advancement in extraction techniques and lower cost of electricity generation. Two hundred years ago, the extraction technology was not as advanced and this resulted in less metals able to be extracted and made available for use.

2. Metals differ in their reactivity with other chemicals and this influences their uses.

-Describe observable changes when metals react with dilute acid, water, and oxygen.

By Peter Huynh

Preliminary Chemistry- Dot Points on MetalsReactions with oxygen: Most metals will react with oxygen in the air at room temperature to form metal oxides. When metals react with gases to form new substances, this is called corrosion. Corrosion causes the metal to become weaker.

Metal + Oxygen → Metal Oxide

Reactions with water: Most metals combine with water to form hydrogen and a metal hydroxide.

Metal + Water → Hydrogen + Metal Hydroxide

Reactions with acids: During a reaction, the metal dissolves as electrons are lost and cations are formed. Hydrogen ions from the acid gain these electrons and form hydrogen gas. This is called a redox reaction.

Metal + Acid → Salt + Hydrogen

-Describe and justify the criteria used to place metals into an order of activity based on their ease of reactions with oxygen, water, and dilute acids.

The reactivity of metals can be listed in sequence. Metals on the bottom or further to the left tend to be most reactive.

-Identify the reactions of metals with acids as requiring the transfer of electrons.

During a reaction, the metal dissolves and gives up electron and becomes positively charged. The hydrogen ions gain electrons to form hydrogen gas. Because the reaction involves the transfer of electrons, it is called a redox (reduction – oxidation) reaction. OILRIG

-Outline examples of the selection of metals for different purposes based on the reactivity, with a particular emphasis on current developments in the use of metals.

Metals are used for different purposed depending on many factors such as abundance, ease of extraction, hardness, and reactivity.

Metals with a low reactivity such as gold and silver are used in jewellery because of their shiny lustre and the fact that they do not tarnish easily.

Magnesium, on the other hand, is highly reactive. It is used to protect less reactive metals from corrosion. Magnesium is also highly reactive when burnt in oxygen and is used in flares and some fireworks.

-Outline the relationship between the relative activities of metals and their position on the Periodic Table.

The most reactive metals are in the first group, furthest to the left. Because of their valency, they will easily react with other elements in order to lose electrons.

Generally, the further the metal is to the right of the periodic table, the less reactive it is. This is because the metal tends to want to keep its electrons more.

-Identify the importance of first ionization energy in determining the relative reactivity of metals.

The first ionization energy is the energy needed to remove the first electron from an element in the gaseous state.

The less energy required removing the first electron from an element, the more reactive it is. This is because it is easier for the electron to give electrons to another element.

3. As metals and other elements were discovered, scientists recognized that patterns in their physical and chemical properties could be used to organize the elements in the periodic table.

-Identify an appropriate model that has been developed to describe the atomic structure

Bohr’s model: The nucleus is in the centre of the atom and contains protons and neutrons. The electrons are around the nucleus orbiting in electrons shells represented by circles.

By Peter Huynh

Preliminary Chemistry- Dot Points on Metals-Outline the history of the development of the Periodic Table including its origins, the original data used to construct it and the predictions made after its construction

1800s: Around 30 elements were known. Antoine Lavoiser classifies the elements into metals and non-metals.

1829: Dobereiner, a German scientist, recognizes physical and chemical similarities among groups of 3 elements. He calls these groups “Triads”.

1864: About 40 elements had been discovered. John Newlands proposes law of octaves where elements were ordered according to atomic weight.

1869: Russian chemist Mendeleev proposes the periodic law where elements are ordered according to atomic weight.

1914: British chemist Henry Mosely proposed a modified version of Mendeleev’s law where elements were ordered according to their atomic numbers.

-Explain the relationship between the position of elements in the Periodic Table and:

*Electrical Conductivity

*Ionization Energy

*Atomic Radius

*Melting/Boiling Point

*Valency

*Electronegativity

*Reactivity

Property Trend going across

Trend going down

Electrical Decreases as Increases

Conductivity elements get less metallic

Ionization Energy

Increases as elements get less metallic

Decreases as electrons further from nucleus

Atomic Radius Decreases as the nucleus gets more positive

Increases as there are more shells

MP/BP Increases from group I to IV but then decreases

Decreases from group I to IV but then increases

Valency Decreases as elements get less metallic

Increases

Electronegativity Increases Decreases

Reactivity Decreases Increases

Electronegativity: Tendency of an atom to attract electrons

4. For efficient resources use, industrial chemical reactions must use measured amounts for each reactant.

-Define the mole as the number of atoms in exactly 12g of carbon-12.

A mole is simply a number of atoms. That number is known as Avogadro’s number and its value is the exact number of atoms in 12g of carbon-12: 6.02 x1023.

-Compare mass changes in sample of metals when they combine with oxygen.

The total mass of the system remains constant in a chemical reaction. When metals react with oxygen in the air, they generally form metal oxides. The oxygen combines with the metal and adds mass to the original metal.

By Peter Huynh

Preliminary Chemistry- Dot Points on Metals-Describe the contribution of Gay-Lussac to the understanding of the gaseous reactions and apply this to an understanding of the mole concept.

Gay-Lussac contributed to the understanding of gaseous reactions by discovering that gases always combine in whole number ratios.

-Recount Avogadro’s law and describe its importance in developing the mole concept.

Avogadro stated that “Equal volumes of all gases, measured of the same temperature and pressure, contain equal numbers of molecules.”

-Distinguish between empirical and molecular formulae.

The molecular formula is exactly how many of each element are present in a molecule whereas the empirical formula is a simple whole number ratio of the elements in a molecule.

5. The relative abundance and ease of extraction of metals influences their value and breadth of use in the community.

-Define the terms mineral and ore with reference to economic and non-economic deposits of natural resources.

Minerals are naturally occurring inorganic substances of a metal found in the Earth’s crust.

Ores are a deposit of minerals considered to be economically worth mining for the extraction of one or more metals.

-Describe the relationship between the commercial prices of common metals, their abundances, and relative costs of production.

The commercial price of a metal depends on many factors such as:

-Abundance: Greater abundance means higher supply which means lower price.

-Cost of extraction: More reactive metals are more expensive since it takes more energy to extract them.

-Location: If the ore is in a remote place, the cost of extraction would be greater and therefore the price would increase.

-Explain why ores are non-renewable resources.

Ores were formed during the evolution of the universe and planets and are therefore non-renewable resources.

-Describe the separation processes, chemical equations and energy considerations involved in the extraction of copper from its one of ores.

1) Mining, crushing, and grinding (physical change)

2) Froth floatation- The copper minerals adhere to the solution and rise to the top and are collected. (physical change)

3) Roasting and smelting- The copper is roasted in air.

2CuFeS2s+4O2g→Cu2Ss+2FeO s+3SO2g

The mixture is then heated with sand to a sufficiently high temperature. This produces two immiscible liquids.

FeOs+SiO2s→FeSiO3l

The liquid FeSiO3is removed. The copper (I) sulfide is then heated on its own to a higher temperature while air is bubbled through it. This reduces sulfide to copper metal and sulfur dioxide is produced.

CuSl+O2g→2Cul+SO2g

The liquid copper is left to cool and solidify.

-Recount the steps taken to recycle aluminum.

1. Recyclable materials collected from homes, businesses etc.

2. Materials transported to a central processing plant.

By Peter Huynh

Preliminary Chemistry- Dot Points on Metals3. Aluminum is obtained through melting the recyclable materials and is put into ingots to be reused.

By Peter Huynh