topic 2 - energy changes Flashcards
properties of solids
fixed shape and volume
cannot be compressed
have a regular arrangement
are tightly packed, particles are touching each other
vibrate about their position
have strong forces of attraction holding them in position
properties of liquids
no fixed shape, but take the shape of their container
fixed volume
can flow
cannot be compressed
have no regular arrangement
are tightly packed, particles are touching each other
move randomly at different speeds
do not move far as they frequently collide with other particles
have weaker forces of attraction compared to solids
properties of gases
no fixed shape, but take the shape of their container
do not have a fixed volume, but take up the volume of their container
can flow
can be compressed
have no regular arrangement
move randomly at different speeds, but much faster than liquids
have very weak forces of attraction compared to solids
Forces of attraction
Forces that exist between atoms or molecules that pull or attract the particles to each other. Known as intermolecular forces.
particle model
A theoretical model to explain the arrangement and movement of particles in all states of matter.
summary of changes of state
…to solid …to liquid …to gas
From solid… – melting (sublimation)
From liquid.. freezing – evaporating
From gas… (deposition) condensing –
kinetic particle theory
A theory used to describe and explain the behaviour of substances in each state of matter. The fundamental premise to kinetic theory is that particles are always moving.
kinetic energy
A store of energy transferred when an object moves. Object moving quickly have more kinetic energy than those moving slowly.
solid to liquid (melting)
Particles in the solid state vibrate around a fixed point.
As more energy is supplied, the vibrations of the particles increase.
When particles have enough energy to overcome the forces of attraction, they begin to move past each other.
liquid to gas (boiling)
Particles in the liquid state move past each other.
As more energy is supplied, the particles gain energy and move faster.
When particles have enough energy, they overcome the forces of attraction and break free from the liquid.
gas to liquid (condensation)
Particles in the gaseous state move freely, quickly and randomly.
As the gas cools, energy is removed.
The particles slow down.
Eventually, they no longer have enough energy to overcome the forces of attraction.
liquid to solid (freezing)
Particles in the liquid state overlap and move past each other.
As the liquid cools, more energy is removed from the particles and they slow down.
The forces of attraction pull the particles together into a regular arrangement.
The particles remain in their positions and vibrate around a fixed point.
pressure
A measure of the force which the particles in a container exert on the surface as the particles collide with it.
concentration gradient
The difference in concentration of a fluid (liquid or gas) between two connected areas.
diffusion
is the movement of particles from an area of high concentration to an area of low concentration and continues until the concentration of the gas is uniform throughout.
exothermic reaction
A reaction that gives out energy to the surroundings, usually as heat.
endothermic reaction
A reaction that takes in energy from the surroundings, usually as heat.
neutralisation reactions
A reaction between an acid and a base or an alkali to produce a neutral salt and water.
reaction pathway diagrams
Graphical method for showing the changes in energy levels during a chemical reaction.
activation energy
The minimum energy required for a reaction to happen.
enthalpy change
The difference in energy between reactants and products. Units in kJ/mol with symbol ΔH .
surplus
Excess or extra.
bond energy
The amount of energy in kJ/mol that is needed to break one mole of a bond.
saturated
Molecules that contain only single carbon to carbon bonds.
covalent bonds
A force of attraction between shared pairs of electrons and the nuclei of two atoms.
functional group
An atom of a group of atoms in an organic compound that gives rise to the particular chemical reactions of that compound.
incomplete combustion
When combustion of a substance occurs with insufficient oxygen. If carbon-containing substances are being combusted then carbon monoxide will be produced.
substitution reactions
A chemical reaction when an atom on a molecule is replaced by another.
choloroalkanes
Organic compounds produced by the substitution reaction between chlorine and alkanes.
monosubstitution
A substitution reaction in which only one hydrogen is replaced by another type of atom. For example, chloromethane.
fermentation
A chemical reaction that is used to convert glucose into alcohol with the use of yeast as a catalyst.
addition reaction
The chemical reaction when a double bond is broken in an alkene resulting in the addition of atoms to the molecule.
volatile
The property of a material describing how easily it vaporises (evaporates).
biofuel
Fuels derived from plant based materials such as bioethanol and biodiesel. They have the advantage over conventional fossil fuels of being renewable.
