1.1. Introduction to the particulate nature of matter Flashcards
Classifications of matter
Pure vs Mixtures
Pure = Elements, compounds
Mixtures = Heterogenous, homogenous
Element
An element is a pure chemical substance composed of atoms with the same no. of protons in the atomic nucleus.
Cannot be divided into simpler substances.
Atom
Smallest particle of an element to show the characteristic properties of that element.
Native state
The occurrence of an element in an uncombined or free state in nature.
Compounds
A substance made by chemically bonding together two or more elements in a fixed ratio of atoms.
Mixture
Contains more than one element or compound in no fixed ratio, which are not chemically bonded together.
The components of a mixture can be separated by physical methods.
eg. Air, water
Homogenous mixture
A mixture with uniform composition and properties throughout.
The inter-particle attraction within the different components must be similar in nature to those between the components in the mixture.
eg. Solution of salt water
Heterogenous mixture
A mixture with a non-uniform composition. Its properties are not the same throughout.
Eg. Water and oil
Filtration
What are the components separated called?
Process in which a solid is separated from a liquid or gas using a membrane.
Collected solid = Residue
Liquid passed through = Filtrate
Distillation
Used to seperate a solvent from a solute.
Solvent has a lower boiling point than solute. Heated until evaporating.
Passed through a condensing tube filled with cold water. Gas condenses into liquid + is collected in a beaker.
Paper chromatography
Small spots of solution are placed along a baseline (drawn in pencil)
Paper is suspended in water and saturated
Solvent (water) begins to climb paper, components separate with water depending on mass + solubility.
Used to investigate components of food colouring / amino acids.
State of matter
Different energies of particles.
Gas, liquid, solid
At a given temp. determined by the strength of inter-particle forces that exist between the particles relative to this average kinetic energy.
eg. if inter-particle forces are strong enough to keep in position at a given temp. + press. = solid. If not = gas or liquid.
Solid - Properties
- Particles closely packed (lattice)
- Inter-particle forces strong, particles vibrate in position
- Fixed shape
- Fixed volume
Liquid - Properties
- Particles more spaced
- Inter-particle forces weaker, particles can slide over each other
- No fixed shape
- Fixed volume
Gas - Properties
- Particles fully spread out
- Inter-particle forces negligible, particles move freely
- No fixed shape
- No fixed volume
Fluids
Gas + liquid –> Ability to flow
Diffusion
Process by which the particles of a substance spread out more evenly, as a result of their random movement.
Occurs in fluid states.
Speed of diffusion
Kinetic energy
Ek = 1/2mv²
Average kinetic energy of all particles at the same temp, is the same –> inverse relationship between mass and velocity
1/2 mava² = 1/2mbvb²
ma/mb = va²vb²
Thus, particles with smaller mass diffuse faster than those with greater mass at the same temp.
State symbols
Solid - (s)
Liquid - (l)
Gaseous - (g)
Aqueous (aq)
Solute vs solvent vs solution
Solution = mixture of two components
Less abundant component = Solute
More abundant component = Solvent
Solute could be gas, liquid, solid.
Solvent is usually a liquid.
Solutions in water always have state symbol (aq)
Fixed point
Defined melting point + boiling point.
Pure substances have these
State changes
Gas –> Liquid = Condensing
Liquid –> Solid = Freezing
Solid –> Gas = Sublimation
Solid –> Liquid = Melting
Liquid –> Gas = Evaporating
Gas –> Solid = Deposition
Deposition occurs when snow / frost forms.
Boiling vs Evaporation
Boiling occurs at a fixed temperature throughout the liquid.
–> Temperature at which vapour pressure is equal to external pressure.
–> When external pressure is lower, vapour pressure needed to boil reduces –> Boils at a lower temp.
Evaporation occurs at any temperature, at the surface.
Temperature changes during state changes
Temperature remains the same during a state change. All energy si being used to break bonds.
Bond breaking = Endothermic (requires energy)
Bond making = Exothermic (gives out energy)
During bond making temp changes, temp remains the same, since all energy is being given out.
Kelvin
SI unit of temperature.
Absolute 0 = -273 C –> No kinetic energy
5 kelvin = -268 C
Temp inc. of 1C = Temp inc. of 1 K
How is the temperature of particles measured?
In a sample there are several particles with different kinetic energies.
Average kinetic energy of sample is taken.
Total kinetic energy is conserved in particle collisions, whereas individual particles change their kinetic energy in each collision. Momentum is conserved.
Maxwell-Boltzmann distribtution
The statistical distribution of energies in a sample at a particular temperature.
Distribution allows us to understand the effect of temperature on rates of reaction.
