Page 19 - Curriculum Visions Dynamic Book

 This picture shows a detail of the Hoffman’s voltameter, some time after the power has been applied. The indicator measures the amount of hydrogen ions in the water,
that is, the amount of water that has been dissociated so that the water and hydrogen ions can move freely. The hydrogen ions recombine to hydrogen gas molecules in one tube (above the blue-stained water). The oxygen forms in the tube where the indicator has turned the water red.
bond: chemical bonding is either a transfer or sharing of electrons by two or more atoms. There are a number of types of chemical bond, some very strong (such as covalent bonds), others weak (such as hydrogen bonds). Chemical bonds form because the linked molecule is more stable than the unlinked atoms from which it formed. For example, the hydrogen molecule (H2) is more stable than single atoms of hydrogen, which is why hydrogen gas is always found as molecules of two hydrogen atoms.
dissociate: to break apart. In the case of acids it means
to break up forming hydrogen ions. This is an example of ionisation. Strong acids dissociate completely. Weak acids are not completely ionised and a solution of a weak acid has a relatively low concentration of hydrogen ions.
electrolysis: an electrical–chemical process that uses an electric current to cause the break up of a compound and the movement of metal ions in a solution. The process happens in many natural situations (as for example in rusting) and is also commonly used in industry for purifying (refining) metals or for plating metal objects with a fine, even metal coating.
electrolyte: a solution that conducts electricity.
ion: an atom, or group of atoms, that has gained or lost one or
more electrons and so developed an electrical charge.
Two volumes of hydrogen collect for every one of oxygen (the formula for water is H2O).
Oxygen
Hydrogen
+
EQUATION: Dissociation of water to yield oxygen
Water ➪ hydrogen + oxygen 2H2O(l) ➪ 2H2(g) + O2(g)
➡
Pure water, that is, water consisting only of water molecules with no impurities, is a poor conductor of electricity. However, the water we normally call pure water (meaning fit to drink) has many minerals dissolved in it. These minerals will dissociate easily, allowing ions to flow through the water and electrons to move through the wires of the external circuit.
Also...
19
19