Chemistry - Separating techniques and atomic structure.

Element.

Consists of 1 type of atom only.

Compound.

A mixture of 2 or more elements that are chemically combined.

Mixture.

Two or more elements or compounds that are not chemically combined.

Solvent.

The liquid in which the solute dissolves.

Solute.

The substance is being dissolved.

Solution.

Formed when the solute has dissolved in the solvent.

Soluble.

A substance that will dissolve.

Insoluble.

A substance that will not dissolve.

Filtration.

This technique separates substances that are insoluble in a solvent from those that are soluble. Filtration works by only allowing the soluble particles through the filter and leaving the insoluble substances in the filter.

Crystallisation.

This technique separates a soluble substance from a solvent by evaporation. Because the water has a lower boiling point than salt so the water evapourates just leaving the salt in the bottom.

Disstillation.

This technique separates liquids by evaporating the liquid with a lower point and cooling the vapour.

On the distillation diagram, the water in is on the _______.

bottom.

On the distillation diagram, the water out is on the ___________.

top.

Chromatography.

This technique separates small amounts of dissolved substances by running a solvent along absorbent paper. Chromatography involves a stationary phase and a mobile phase.

Mobile phase ( chromatography ).

The component that moves ( water ).

Stationary phase.

The component that doesn’t move ( paper )>

Rf ( definition ).

Retention factor.

Rf ( formula ).

distance spot travelled / total distance.

What are atoms made up of?

Protons, neutrons and electrons.

Radius of an atom.

0.1nm

1 nanometer ( nm ) in meters ( m ).

1 × 10 (-10)

The nucleus.

The nucleus is in the middle of the atom, it contains positive protons and neutral neutrons and therefore has a positive charge. It is about 1/10,000 of the radius of an atom but contains almost the whole mass.

Atomic number.

Number of protons ( equal to the number of electrons ).Top number.

Atomic mass number.

Number of protons + neutrons in the nucleus.

Isotopes.

Isotopes are different forms of the same element which have the same number of protons but a different number of neutrons. So they have the same atomic number but different mass number. A very popular isotope example is carbon 12 and 13.

Formula for relative atomic mass.

relative atomic mass = sum of ( isotope abundance x isotope mass number ) / sum of abundance of all the isotopes.