C1 - Particles Flashcards
Describe the structure of solids
There are strong forces of attraction between particles, which hold them in fixed positions in a very regular lattice arrangement
The particles do not move from their positions, thus do not flow
The particles vibrate about their positions - the hotter the solid becomes, the more they vibrate (causing them to expand slightly when heated)
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Describe the structure of liquids
There is some force of attraction between the particles.
They are free to move past each other, but they do tend to stick together
Liquids don’t keep a definite shape and will flow to fill the bottom of a container
The particles are constantly moving with random motion
The hotter the liquid gets, the faster they move which causes them to expand slightly when heated.
Describe the structure of gases?
There is next to no force of attraction between the particles - they are free to move
They travel in straight lines and only interact when they collide
Gases don’t keep a definite shape or volume and will always fill any container
When particles bounce off the walls of a container, they exert a pressure on the walls
The particles move constantly with random motion. The hotter the gas gets, the faster they move.
Gases either expand when heated, or their pressure increases
Why can you not compress a substance in the solid or liquid state?
There is no space for the particles to move into
Why can’t a substance in the solid state flow?
In the solid state, the particles vibrate around fixed positions and cannot move from place to place
What is a physical change?
A physical change happens when a substance changes state or shape, or breaks into pieces.
No new substances are made and many can be reversed.
Examples of physical changes:
Freezing juice to make an ice lolly
Mixing sand with water
Dissolving sugar in water
What is a chemical change?
A chemical change is a change that produces one or more new substances
During the reaction, bonds between atoms break and the atoms change places - the reactants rearrange themselves to form different products.
The properties of the new substances are often very different from the properties of the original substance
Many chemical changes are difficult or impossible to reverse
Examples of a chemical change:
Cooking eggs, cakes and other foods
Steel rusting
An acid reacting with an alkali to make a salt and water
What is the identified attractive force between particles called?
Electrostatic forces of attraction
Limitations of the particle model:
The forces between particles
The size of particles
The space between particles
What was Dalton’s atomic model?
He described atoms as solid spheres and said that different spheres made up the different elements
What was Thomson’s atomic model?
In 1897, J.J. Thomson concluded from his experiments that atoms were not solid spheres
His measurements of charge and mass showed that an atom must contain even smaller, negatively charged particles - electrons
He changed the ‘solid sphere’ idea into a new model known as the ‘plum pudding model’
What did Ernest Rutherford investigate?
In 1909, Rutherford and his students Geiger and Marsden, conducted the famous gold foil experiment.
They fired positively charged alpha particles at an extremely thin sheet of gold
What was Rutherford’s results from the gold foil experiment?
From the plum pudding model, they were expecting the particles to pass straight through the sheet, or be slightly deflected at most.
Whilst most of the particles did go straight through, some were deflected more than expected and very few were deflected backwards.
