C1 - Particles

Describe the main features of the particle model.

Solid:

Regular arrangement, touching. During melting, the particles lose their regular arrangement but remain touching, and vice versa for freezing

Liquid

Irregular arrangement, touching. During boiling, the particles stop touching and vice versa for condensing.

Gas

Irregular arrangement, not touching, and moves freely around spaces. 

Explain in terms of the particle model the distinction between physical changes and chemical changes.

In physical changes, the particles are simply rearranged.

In chemical changes, bonds are broken and made, and atoms change places, rearranging to form new chemicals.

Limitations of the particle model

Does not take into account forces of attraction, size of particles, or the space between them and may not show the full atom.

Describe how the atomic model has changed over time.

1897 - JJ Thomson found that atoms may contain smaller negatively charged particles, and proposed the plum pudding model.

1909 - Rutherford conducted the gold foil experiment - shooting alpha particles at a thin piece of gold foil, and his results gave birth to the nuclear model.

Scientists realised that this would cause the atom to collapse and Bohr then created the atomic model.

Describe the atom

Positively charged nucleus surrounded by negatively charged electrons in fixed positions in fixed energy levels.

Recall the typical size (order of magnitude) of atoms and small molecules

1x10^-10m

Recall relative charges and approximate relative masses of protons, neutrons and electrons

Proton = Charge +1, Mass 1

Neutron = Charge 0, Mass 1

Electron = Charge -1, Mass 0.0005

Calculate numbers of protons, neutrons and electrons in atoms and ions, given atomic number and mass number of isotopes.

Protons = Atomic Number = Electrons

Neutrons = Mass Number - Atomic Number