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