C3 Revision

Relative of atomic mass.

Arranged them so that groups of elements with similar properties fell into vertical columns in his table.

Ordered elements by atomic weight

Included only the elements known at the time

Maintained a strict order of atomic weights

Every eighth element had similar properties (Newlands’ Law Of Octaves)

Was criticized by other scientists for grouping some elements with others when they were obviously very different to each other

Ordered elements by atomic weight

Left gaps for elements he predicted would be discovered later

Swapped the order of some elements if that fitted their properties better

Elements in groups had similar properties

Was seen as a curiosity to begin with, but then as a useful tool when the predicted elements were discovered later

H2CO3(aq) + CaCO3(s) → Ca(HCO3)2(aq)

• A known volume of water is put into a conical flask.
• Soap solution is added to it from a burette or pipette.
• The mixture is swirled to help it form lather.
• The volume of soap solution that needs to be added to form permanent lather is recorded.
• The harder the water, the greater the volume of soap solution needed.

By boiling it.

can improve the taste of the water

are good for the development and maintenance of bones and teeth

can help to reduce heart disease

More soap is needed to produce lather, which increases costs. This happens with temporary or permanent hardness.

The scum produced is unsightly - spoiling the appearance of baths and shower screens, for example.

• Temporary hardness can reduce the
• efficiency of kettles and heating systems.
• This is because limescale
• (a solid containing calcium carbonate) is
• produced when the water is
• heated. It coats the heating element in kettles, and the inside of
• boilers and hot water pipes. This means more energy is needed to heat
• the water, again increasing costs. Pipes may become blocked by
• limescale - causing the heating system to break down