C1

Describe a solid in terms of particles

Very closely packed particles in a regular arrangement. This is due to strong forces of attraction between them. They have low energy so they vibrate around a fixed position

Describe a liquid in terms of particles

They are closely packed but in a random arrangement. This is due to weaker forces of attraction between them. They have medium energy so they can move around each other.

Describe a gas in terms of particles

The particles are far apart in a random arrangement due to weak forces of attraction between them. They have high energy so they move quickly in all directions

Difference between a physical change and chemical change

Physical change- no new substances are made and changes can be often easily reversed (eg changes of state)
Chemical change- new substances are made and the changes aren’t easily reversed (eg cooking an egg)

How to calculate the ratio of distance to diameter of atoms

Ratio of distance to diameter = distance between atoms/diameter of atoms

Limitations of the particle model?

Does not take into account:
Force between particles
Size of particles
Space between particles

Describe the structure of an atom

Atoms consist of a central nucleus which contains protons and neutrons
The nucleus is small compared to the rest of the atom
The nucleus is surrounded by electrons in shells

Average size of an atom?

The average size of an atom is 1×10^(-10)

What does the atomic number and mass number of an atom show

Atomic number- number of protons/electrons in an element
Mass number- TOTAL number of protons+neutrons in an element

Describe the plum pudding model and who discovered it

J.J Thomson theorised that an atom consisted of a ball of positive charge, with negative electrons mixed throughout it

Describe Rutherford’s experiment to develop the nuclear model

In Rutherford's experiments, alpha particles were fired at a thin sheet of gold foil.
Most particles passed through, but some were deflected off course. 
This caused him to hypothesise that there was a dense region of positive charge at the centre of the atom that repelled the alpha particles.
As a result, he developed the nuclear model of the atom, in which there was a central positive nucleus, surrounded by negative electrons. 

What did Bohr say to build upon Rutherford’s theory

One issue with the nuclear model was that the atom should collapse as the negative electrons would be attracted to the positive nucleus.
In response to this, in 1913 Bohr suggested that electrons orbit the nucleus in shells, which prevents the atom from collapsing.