topic 1 - atomic structure

Question 1

what is a mixture?

Answer 1

a mixture consists of two or more elements or compounds not chemically combined together; it does have the same chemical properties

Question 2

what are the methods through which mixtures can be separated?

Answer 2

• filtration, crystallisation, simple distillation, fractional distillation and chromatography
• they do not involve chemical reactions

Question 3

how does simple distillation work?

Answer 3

simple distillation is used to separate liquid from a solution - the liquid boils off and condenses in the condenser. The thermometer will read the boiling point of the pure liquid

Question 4

how does evaporation work?

Answer 4

• evaporation is a technique for the separation of a solid dissolved in a solvent from a solvent
• the solution is heated until all the solvent evaporates; the solids stays in the vessel

Question 5

how does crystallisation work?

Answer 5

• crystallisation only removes some of the solvents by evaporation to form a saturated solution
• then, we cool down the solution
• the solids start to crystallise, as they become less soluble at lower temperatures. the crystals can be collected and separated from the solvent via filtration

Question 6

how does fractional distillation work?

Answer 6

• fractional distillation is a technique for the separation of a mixture of liquids
• it works when liquids have different boiling points
• the apparatus is similar to the one of simple distillation apparatus, with the additional fractionating column placed on top of the heated flask

Question 7

what is an isotope?

Answer 7

atoms of the same element that have the same number of protons but a different number of neutrons

Question 8

what are the elements in group 1 known as?

Answer 8

the alkali metals

Question 9

what are three characteristics of alkali metals

Answer 9

• all have one electron in their outer shell
• lower density
• are stored under oil - to prevent reactions with oxygen and water
• soft (can be cut with knife)

Question 10

how do group 1 elements react with non-metals?

Answer 10

they form ionic compounds which are soluble white solids that dissolve in water to form colourless solutions - they all have one electron in their outer shell

Question 11

how do group 1 elements react with water?

Answer 11

• they release hydrogen and form hydroxides which dissolve to form alkaline solutions
• react vigorously with water fizzing and moving around on the surface of the water

Question 12

how does reactivity change moving down group 1? Why?

Answer 12

• reactivity increases as the atoms get larger and the distance between the nucleus and the outer electrons increases and thus attraction from the nucleus decreases, allowing them to lose electrons more easily

Question 13

what are the properties of transitional elements?

Answer 13

• hard and strong metals
• high melting points (apart from mercury)
• high density
• much less reactive than with group 1 metals
• can form ions with different charges
• form coloured compounds