TWEED RIVER HIGH SCHOOL



TWEED RIVER HIGH SCHOOL

2006

PRELIMINARY CHEMISTRY

Unit 1

The Chemical Earth

Part 2

• Although most elements are found in combinations on Earth, some elements are found uncombined.

Abundance of Elements in zones of the Earth.

1. The lithosphere:

|Element |% by weight |

|Oxygen |50.0 |

|Silicon |26.0 |

|Aluminium |7.5 |

|Iron |5.0 |

|Calcium |3.5 |

2. The Hydroshpere:

|Element |% mass |

|Oxygen |86.0 |

|Hydrogen |10.75 |

|Chlorine |1.90 |

|Sodium |1.06 |

3. The Biosphere (Living Cell)

|Element |% Mass |

|Oxygen |60.0 |

|Carbon |21.0 |

|Hydrogen |11.0 |

|Nitrogen |3.5 |

|Calcium |2.5 |

4. The Atmosphere: As per part 1

• Explain the relationship between the reactivity of an element and the likelihood of it existing and an uncombined element.

Reactivity of elements.

The reactivity of an element, in general, depends on the number of electrons in its outer shell.

Elements in Groups 1 , 2, 3, 5, 6 and 7 are very reactive and are not found in their elemental state in nature.

The group 8 elements, the noble gases are not reactive and are found in their elemental state in nature.

Some metals such as gold and silver are also unreactive and are found in their natural state in nature.

• Classify elements as metals, non-metals and semi-metals according to their physical properties.

1. Metals

Typical metals share the following physical properties:

• Relatively high densities.

• Good conductors of heat and electricity

• Malleable and ductile.

• Have a shiny surface (Lustre)

• Relatively high melting points

2. Non-Metals

• State and form is variable

• Usually not lustrous

• Poor conductors of heat and electricity

• Not malleable or ductile

• Variable melting points

3. Semi-Metals

• Also known as metalloids

• Semi-metals have a wide rage of properties which are a combination of the properties of metals and non-metals.

Practical Assignment

• Plan and perform an investigation to examine some physical properties, including malleability, hardness and electrical conductivity and some uses of a range of common elements to present information about the classification of elements as metals, non-metals and semi-metals.

Your investigation must include the following points:

• Aim

• Risk Assessment

• Method

• Results

• Discussion

• You will then perform the experiment in the lab.

You will be given a list of elements available to you.

Assignment

• Analyse information from secondary sources to distinguish the physical properties of metals and non-metals.

You are to prepare a table outlining to outline the different physical properties of metals and non-metals. Place the table in the space below.

• Account for the uses of metals and non-metals in terms of their physical properties.

Choosing the right metal for the job

|Metal |Properties |Uses |

|aluminium |low density, does not corrode |suitable for the bodies of planes |

|[pic] | | |

|copper |good conductor of electricity, does not |electrical wires as it is a good conductor |

|[pic] |react with water |water pipes due to its low reactivity |

|gold |very good conductor of electricity, |electrical connections on circuit boards - due|

|[pic] |unreactive |to its conductivity |

| | |jewellery - due to its lack of reactivity |

|steel |cheap and strong |suitable for building material |

|[pic] | | |

[pic]

Assignment

• Process information from secondary sources and use a Periodic Table to present information about the classification of elements as:

- metals. non-metals and semi-metals

- solids. Liquids and gases at 25°C and normal atmospheric pressure.

Use the following two Periodic Tables to present your information.

Use the first Periodic Table to represent metals, non-metals and semi-metals, and the second Periodic Table to represent solids, liquids and gases.

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