Q2 Different metals were discovered at different times throughout history. In general, more reactive metals were discovered much more recently than less reactive metals.
Very unreactive metals, such as gold, were discovered in ancient times.
a) Suggest an explanation for the link between a metal's date of discovery
and its reactivity.

The first metal known to be prepared from its ore was copper, perhaps as early as 6000BC6000BC in the Middle East. The ore, which contained copper(II) oxide, was heated with charcoal, which was prepared by the incomplete burning of wood, and is mainly elemental carbon. Later, iron and tin were prepared in the same way. Bronze, an alloy of copper and tin, was made by mixing copper-containing ore with tin ore and heating the mixture in the presence of charcoal. 

aquifers are bounded above and below by impermeable rock. the driving force of groundwater movement in confined aquifers is pressure, rather than gravity.

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.