Chemistry Exam
Compounds
Atoms
Elements
Dissolving
Reactions
Energy of Particles and Matter
Proton
Neutron
Electron
Positive Charge
No Charge
In the nucleas
Determines what element the atom is
Very small
Orbits the nucleas at extreme high speeds
Vital for reactions
The substance is only made out of one type of atom
The substance is made out of two or more types of atoms
Liquid
Gas
Solid
The atoms have a lot of energy and it overcomes the attractive forces of particles
Multiple atoms can bond to form molecule/s
The atoms have some energy and it partially overcomes the attractive forces.
They can vary in volume and expand to fill up their container
They take the shape of their container
Can be poured
Cannot be poured
They have a fixed shape and volume
They have no energy to overcome the attractive forces
Particles in solids are tightly packed together so they cannot be compressed any further. Gases are loosely packed and have lots of air around them so it's easy to
Matter will change from solid to liquid at the melting point, from liquid to gas at the boiling point, liquid to solid at the freezing point
Evaporation is when water turns into gas without being at 100 degrees through wind. Boiling is when the water turns into gas at the boiling point.
Water vapour is low in energy steam is high in energy
When gas changes to liquid it's called condensation as the gas touches a cold surface its thermal energy is lost and so it turns into liquid
Particle Arrangements
Crystals have regular faces and edges
Amorphous substances do not have a regular structure to them
Crystals occur when particles form in crystal lattices
Particles of an amorphous substance do not arrange into any regular arrangement/shape
Physical Process
The solid solute is put into a liquid solvent which dissolves into a solution as it spreads out
This is different to melting as it only involves two substances mixing not heated
The attractive forces between the solute particles and the solvent particles cause the solid particles to fall apart.
A solute will only dissolve if the attractive forces between the solute and the solvent is stronger than the attractive forces within the solute itself
A solution is saturated when no more particles can dissolve in it
If a solution is heated its solubility is increased
Diffusion occurs when particles of a solute move through a solvent by random (natural particle movements) to form a solution which is even in the particles
Pure substances
There are 92 naturally occurring elements
Cannot be broken down any further
Mixtures
The atoms are not chemically bonded together
Homogenous
Heterogenous
Evenly mixed
Unevenly mixed
Naming
Every element has a name and a symbol which represents the element
Compound names come from the elements which form it
Separation
Water may be separated from other chemicals by boiling/evaporating it
Mixtures can be separated by filtering or decanting out larger particles
Models are often used to show the structure of an atom based on its relative size and are differentiated with colour
A lot of empty space between the electrons and the nucleas
Atoms are stable when the number of Protons are the same as the number of Electrons there are
When atoms react they either lose or gain electrons
Elements which are not noble gases cannot be found as a single atom, but as a molecule with 2 or more atoms, called polyatomic ions so the electrons all have full outer shells
Physical and Chemical Change
Physical change is the rearrangement of the same particles, with no new element added - reversible
Chemical change involves change to the particles itself to dismantle old particles to form new substances - non-reversible
Reactants ⟶ Product/s
Chemical properties are how a chemical would react with other substances, eg. water, air and acid
When chemicals react there are often observations including:
- light given off
- new substance forming
- gas production
- burning
- heat release
- colour change
- smell
Chemical reactions are often written down with chemical equations. These can be word equation, chemical formulae
Acids
Mineral Acids come artificially from minerals while organic acids are made by living things and all contain the element carbon.
Organic Acids: Citric, Tartaric, Acetic
Mineral Acids: Hydrochloric, Sulfuric, Nitric
Acids must all release Hydrogen ions (H\( ^{+} \)) when dissolved into solution
Bases
Must all release Hydroxide Ions (OH\( ^{-} \)) when dissolved
Indicators
Litmus paper can be red or blue. If natural, stays red or blue. If acid, both red. If base, both blue
Universal Indicators can identify how acidic or basic a substance is
pH Levels 1-6 - Acidic
ph Levels 8-14 - Basic
ph Level 7 - Neutral
Base
Neutralisation
The Hydrogen and Hydroxide ions react together to form water, and the rest of the chemical forms a salt.
Acid + Base \( \longrightarrow \) Water + Salt
Metal
Carbonate
Acid + Metal \( \longrightarrow \) Hydrogen + Salt
Acid + Carbonate \( \longrightarrow \) Water + Carbon Dioxide + Salt