Section 1: Principles of Chemistry Flashcards
Name the process responsible for the following changes: solid ⇄ gas
Sublimation (s → g)
Deposition (g → s)
What is diffusion?
It is the overall movement of particles from an area of high concentration to an area of low concentration.
E.g. a gas will diffuse through all the space it can find
E.g. if you spray some perfume in one corner of the room, soon you will be able to feel the smell at the other end of the room.
What is a solubility curve?
It is a curve that shows how the solubility of a substance (in grams per 100g of water) changes with temperature.
Outline the main assumptions of the kinetic theory of matter.
a) Matter is made up of atoms, molecules and ions of different sizes.
b) At the same temperature, small particles move faster than large particles
c) As the temperature rises, the particles have more kinetic energy and move faster
d) Solids are made up if ordered arrangement of closely packed particles
e) Liquids do not have particles arranged regularly ∴ particles can move around
f) In gases, the particles are far apart ∴ move fast ∴ random motion
Explain what is meant by centrifuging
It is a method for separating out particles of different densities in a substance.
It can be used to separate suspended solid (very small particles of a solid) from the liquid they are suspended in.
Used when the particles are so small they can’t be separated via filtration
In a centrifuge, the sample is spin at high rates ∴ forces the solid particles to settle down at the bottom of the tube ∴ the liquid can be decanted.
What is an atom?
An atom is the smallest particle of a chemical element that can exist.
What is an element?
An element is a substance made up of only one type of atom.
How are the elements listed and approx how many are there?
Listed in the periodic table; appox 100
Elements can be classified into two groups based on their properties; what are these groups?
Metals and non-metals
Elements may combine through chemical reactions to form new products; what are these new substances called?
Compounds
What is an compound?
Two or more elements combined chemically in fixed proportions which can be represented by formulae.
What is a mixture?
A mixture consists of two or more elements or compounds not chemically combined together ∴ constituent materials keep their own chemical properties but the mixture may have different chemical properties as a whole
What are the methods through which mixtures can be separated? Do these involve chemical reactions?
Filtration, evaporation/crystallisation, simple distillation, fractional distillation and chromatography and they do not involve chemical reactions.
Describe and explain simple distillation.
Simple distillation is used to separate liquid from a solution — the liquid boils off and condenses in the condenser. The thermometer will read the b.p of the pure liquid. Contrary to evaporation, we get to keep the liquid (drips and is collected into a separate beaker).
