C1 Flashcards
What do atoms in the same group tend to have in common?
They share similar properties.
Why must chemical equations be balanced?
No atoms are created nor destroyed during a chemical reaction, so the mass of reactants= the mass of products
List two differences between a mixture and a compound:
-Chemical reactions are needed to separate compounds, physical means can be used to separate mixtures
-Compounds have a fixed proportion, whereas mixtures do not
List four means of separating mixtures:
-filtration
-crystallisation
-chromatography
-distillation
What apparatus would you need for crystallisation?
-evaporating dish
-water bath
-gauze
-tripod
-heat source (Bunsen Burner)
-Petri dish
During crystallisation, what would be the next step after the solution has started to crystallise?
Transfer the solution to a Petri dish where it can cool off at room temperature.
How can distillation be used to remove dissolved impurities from a sample of water?
-Solution boiled to evaporate solvent- leaves impurities in the flask
-Vapour enters a condenser
-Hot vapour cooled and condensed back into a liquid
-Poured into receiving vessel- outcome is distilled water
Why is fractional distillation used?
To separate mixtures of miscible liquids (they dissolve into each other)
i.e. an ethanol and water mixture
Why is it difficult to obtain pure liquids when using simple distillation to separate liquids with similar boiling points?
More vapour is given off by each component before they reach their respective boiling points, causing them to mix again.
How does a fractionating column work?
-The column has a higher temperature at the bottom
-Substances with a higher boiling point will condense more readily onto the glass beads nearer the bottom (high bp= condenses at higher temp)
-The substance w/ lower bp will continue rising and pass through the condenser
What is an application of fractional distillation?
Used in oil refineries to purify oils
Who discovered each of the subatomic particles?
Electron- J.J Thomson
Proton- Ernst Rutherford
Neutron- James Chadwick
Why was the nuclear model of the atom revised?
-Light given out when atoms were heated only had specific amounts of energy
-Suggested electrons orbited in fixed energy levels- energy given out when an excited electron falls from a higher to a lower energy level
What is the approximate radius of an atom?
0.1nm, 1*10^-10m
What is the approximate radius of a nucleus?
0.00001nm, 1*10^-14m
