Section 1: Principles of Chemistry Flashcards
How are the particles arranged in a solid and why?
Tightly packed in uniform lattice arrangement… Close together.. strong forces of attraction between the particles
Define diffusion & an experiment to demonstrate it
The movement of particles from an area of high concentration to an area of low concentration… Potassium Manganate(VII) gradually turns the beaker of water purple/colour spreads out to fill the whole beaker BECAUSE the random movement of the waterparticles is helping it diffuse
Describe what you’d see when cotton wool soaked with ammonia/hydrochloric acid are on opposite sides of a sealed tube & why?
A white ring of precipitate- ammonium chloride- forms where the two gases that the solutions give off (hydrogen chloride and ammonia) meet. The ring is closer to the side wheere the hydrochloric acid was because the ammonia particles are lighter and smaller so move faster
What charge does the nucleus of an atom have and why?
POSITIVE because it contains protons and neutrons: the positive charge of the protons makes it +vely charged. (neutrons have no charge)
In a neutral atom, the no. of electrons is equal to the no. of…
protons
how to find out no. of protons&neutrons from the mass number?
mass number is the two added together. Mass number - atomic no. = neutrons, because atomic no. = protons
What kind of bond holds molecules together?
covalent bonds
When would you use filtration? e.g to separate what from what
to separate an insoluble solid from a liquid (also purification)
When would you use crystillisation?
To separate a soluble solid from a solution
What equipment is needed for filtration?
beaker/FILTER PAPER/funnel
What is the method for crystallising a product?
- Pour solution into an evaporation dish
- Sloly heat solution. Some solvent will evaporate thus solution will become more concentrated. Stop heating when crystals form.
- Remove dish from heat and leave in a warm place for the rest of the solvent to slowly evaporate
- Dry the product using drying oven/dessicator
Method for separating rock salt(mixture of salt and sand)? hint: uses filtration AND crystallisation. Mention equipment.
- Grind up the rock salt with pestle and mortar
- Dissolve in a beaker and stir
- Filter through filter paper in a funnel. Big grains of sand will stay in paper.
- crystallise the remaining solution by evaporation in an evaporating dish over a bunsen
Describe the method of chromatography.
Place paper with pencil line and dots of dyes on rolled up in a shallow solvent. Dye mustn’t touch solvent. Seal container and leave. Dye seprates as solvent travels up paper carrying dyes with it. Each dye moves up at a different rate and forms a spot in a different place.
When is simple distillation used?
To separate a liquid from a solution.
Describe the method of simple distillation.
- Heat solution. The part of the solution with the lowest boiling point will evaporate.
- The vpour is then cooled, condenses and is collected.
- Rest of solution is left behind in flask.
Downside of simple distillation…
you can only use it to separate things with very different boiling points.
a use of simple distillation
to separate sea water: you end up with salt and distilled water
when is fractional distillation used
to separate a mixture of liquids
Method of fractional distillation
- put mixture in a flask with a fractionating column on top. Heat.
- The diff. liquids have diff. boiling points so evaporate at diff. temps.
- Liquid with lowest boiling point evaporates 1st. When temp on thermometer reached its boiling point, the liquid ill reach the top of the column
- liwuids with higher boiling points may also start evaporating. but, as the column is cooler at the to, they’ll only get part of the way up befor condensing and running back down towards flask.
- When 1st liquid had been collected, you raise the temp. until the next one reaches the top
A use of fractional distillation
to fracionally distill crude oil at a refinery
the elements in the periodic table are arranged in order of..
increasing atomic number
an elements group represents…
the number of electrons it has on its outer shell (valency electrons)
The period to which an element belongs represents…
the no. of shells said element has
Group 1 elements are known as the…
alkali metals
Group 7 elements are known as the…
halogens
Group 0/8 elements are known as the…
noble gases
what do the properties of the elements depend on?
the number of electrons they have
the 1st shell / the shell closest to the nucleus has what sort of energy level compared to the other shells?
it has the lowest energy levels
Max. electrons allowed in the 1st shell?
2
Max. electrons in 2nd shell?
8
Max. electrons in 3rd shell+?
8
why does an atom want to react?
because its outer shell is not full
Define ionic bonding
atoms lose/gain electrons to become chargd particles (ions) which re then strongly attracted to one another due to their opposite +ve and -ve charged.
The attraction between ions in ionic bonding is known as…
electrostatic attraction
are atoms missing 1/2 or 7/8 electrons on their outer shell more or less reactive than those with a middleish number of valency electrons? why? and THUS does ionic bonding usually occur between atoms on opposite sides of periodic table or same sides?
they are MORE reactive because they are so close to being ful- they are very keen to gain/lose those 1/2 extra electrons…
Group 1 and 2 elements are metals. What kind of ions do they form and how?
they lose electrons to form +ve ions (cations)
Groups 6 & 7 are non-metals. What kind of ions do they form and how?
they gain electrons to form -ve ions (anions)
How are ions in a Giant Ionic structure held together?(particuklar arrangement)
closely packed 3D lattice arrangement by the attraction between oppositely charged ions (electrostatic attraction)
what are the melting/boiling points of ionic compounds like and why?
they are high bEcause a lot of energy is needed to overcome the strong electrostatic attraction
GIANT IONIC: will a lattice of 2+ and 2- ions be held together with stronger/weaker forces of ttraction than a lattice of 1+ and 1- ions?
stronger
GIANT IONIC: will lattices made up of higher charge ions have higher or lower melting and boiling points than a lattice made up of lower charge ions?
higher
how would a typical row of a sodium chloride ionic structure be arranged? hint: made up of Na+ and Cl- ions…
Na+ Cl- Na+ Cl- Na+ (alternating charges)
Define covalent bonding?
atoms share pairs of electrons: thus they both have a full outer shell.
what is the strong attraction between in covalent bonding?
between the shared electrons and the nuclei of the atoms involved
what kind of bond does the diatomic N2 have?
a triple (covalent) bond!!!
what kind of bond does the diatomic O2 have?
a double (covalent) bond!!
what are Simple Molecular (covalent) Substances made up of?
molecules whose atoms are held together by very strong covalent bonds. However the bonds between these molecules (intermolecular forces) are very weak!
the weak bonds between molecules in a simple molecular substance are called what?
intermolecular forces
As a result of the weak intermolecular forces, the melting/boiling points of simple molecular substances are…because…
very low because the molecules are easily parted from each other :(
what STATE are simple molecular substances normally?
gases or liquids (or easily melted solid)
How are the atoms in Giant Covalent structures held together?
bonded by strong covalent bonds
thre are lots of bond in giant covalent structures. Thus, what are the melting/boiling points like and why?
very high because it takes a lot of energy to break them
Are giant covalent substances usually soluble/insoluble in water?
insoluble
Examples of giant covalent structures that are only made up of carbon atoms? (2)
diamond & graphite
Why is carbon such a good lubricant?
each carbon atom only forms 3 covalent bonds, creating layers which are free to slide over each other
why is graphite the only non-metal which is good at conducting electricity?
because the giant covalent bonding leaves free electrons
Why are diamonds so hard/strong?
because each carbon atom forms four covalent bonds in a very rigid giant covalent structue
Describe & explain the differences between the physical properties of simple molecular substances and giant covalent substances
Simple molecular: low melting/boiling points due to weak intermolecular attraction. Soft or liquid/gas for similar reasons.
Giant covalent: high melting/boiling point because all the atoms are held together by strong covalent bonds which need a lot of energy 2 break. Hard cos rigid giant covalent structure.
what kind of structure do compounds with ionic bonding always have?
giant ionic structures
why do compounds with ionic bonding have high melting and boiling points?
the ions are held together in a closely packed 3D lattice arrangement by the very strong electrostatic attraction between the oppositely charged ions. Therefore a lot of energy is needed to overcome the strong attraction and break the bonds
