Transition elements against Group 1 sim
Weigh cubes of sodium, iron and copper, turn pale green iron(II) yellow-brown with hydrogen peroxide, and time how iron(III) oxide and copper(II) oxide speed up oxygen from hydrogen peroxide while sodium chloride does nothing.
The Periodic Table: transition elements · covers the O-Level, IGCSE, GCSE topic
What the sim shows
Iron and copper are transition elements; sodium is in Group 1. Equal 2.00 cm cubes (8.00 cm³) are weighed: density = mass ÷ 8.00 cm³. Data book (CRC Handbook): sodium 0.968 g/cm³, melts at 98 °C; iron 7.87 g/cm³, 1538 °C; copper 8.96 g/cm³, 1085 °C. Transition metals are much denser and melt much higher (mercury, a liquid at room temperature, is the exception for melting point). They are also stronger and harder, and much less reactive than Group 1 metals: sodium reacts fast with cold water, iron and copper do not. Other transition elements include chromium, manganese, cobalt and nickel. Their ions are coloured: iron(II) pale green, iron(III) yellow-brown, copper(II) blue, while sodium ions are colourless. Iron forms ions with two different charges: acidified hydrogen peroxide oxidises Fe²⁺ to Fe³⁺ (2Fe²⁺ + H₂O₂ + 2H⁺ → 2Fe³⁺ + 2H₂O); sodium only ever forms Na⁺. Many transition elements and their compounds act as catalysts: iron in the Haber process; here, iron(III) oxide and copper(II) oxide speed up 2H₂O₂ → 2H₂O + O₂, and sodium chloride does not. The oxides are not used up: filtered, dried and weighed again afterwards, the powder is still 0.50 g. 20.0 cm³ of 1.00 mol/dm³ hydrogen peroxide can give off at most 0.0100 mol of oxygen, 0.320 g (240 cm³ at room temperature and pressure); the flask on balance B loses that mass as the oxygen escapes through the cotton wool (the gas relights a glowing splint: the test for oxygen). Rates here are illustrative: real ones depend on how finely powdered the oxide is. A 2 cm cube of sodium is far bigger than the pieces used in school; it is shown only to compare densities.
- Iron(II) solution: watch it turn yellow-brown (iron(III)) with hydrogen peroxide
- Balances: A weighs the 2.00 cm cubes; B weighs the flask as oxygen escapes
- Powders: iron(III) oxide, copper(II) oxide, sodium chloride (0.50 g a spatula)
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