Topic 2: Elements, Compounds and Mixtures - Subtopic 1: Purity & Separating Mixtures
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What does it mean if a substance is pure?
• Consist of a single element or compound which contains no other substances
What is a mixture?
• Consists of two or more elements or compounds that are physically mixed together, they are not chemically combined.
What is the difference in melting and boiling point for pure substances and mixtures?
• Pure: Melt and boil at specific temp. • Mixtures: > Range of melting and boiling points > Consist of different substances
What is melting point analysis used for?
• Assess purity of drugs
What is a cooling curve?
• Used to see the influence of impurities • Horizontal show sharp melting point, pure • Gradual decrease, impure
What is the equation for percentage change?
Percentage Change = Final Value - Original Value / Original Value X 100
What is the symbol for relative atomic mass?
Ar
What is the symbol for relative formula mass?
Mr
What does the relative atomic mass refer to?
Average mass of atoms in element
What does the relative molecular mass refer to?
Average mass of atoms in one molecule of element
What is the empirical formula?
Simplest whole number ratio of atoms
How do you figure out the empirical formula of a dot-and-cross diagram?
Count no. of atoms of each element and simplify
How do you figure out the empirical formula of a 3D lattice structure diagram?
• Write ions in lattice • Balance charges
What is the equation for the percentage by mass of an element in a compound?
% mass of an element = Aᵣ x No. of atoms in element / Mᵣ of compound X 100
What is an alloy?
Mixture of metals
What is steel composed of and used for?
• Alloy of Iron + Carbon (I SEE STEEL) • Construction Materials , Appliances, Vehicles
What is stainless steel composed of and used for?
• Alloy of Iron + Chromium + Nickel (I SEE NICE STEEL) • Kitchen Utensils, Surgical Instruments
What is brass composed of and used for?
• Copper + Zinc (CAN’T ZZZ, music too loud) • Musical Instruments, Plumbing
What is bronze composed of and used for?
• Copper + Tin (CHAMPION TIME) • Sculptures, Medals, Bearings
What is duralumin composed of and used for?
• Aluminium + Copper + Manganese + Magnesium (AIRPLANES CAN MAKE MEMORIES) • Aircraft Structures, Automotive Parts
What is a formulation?
A mixture that has been designed as a useful product
Why are alloys stronger and harder than most pure metals?
• Alloys contain atoms of different sizes, which distorts the regular arrangements of atoms • This makes it more difficult for the layers to slide over each other
What is filtration?
• Used to separate undissolved solid from solid liquid solution • Filter paper placed in filter funnel • Paper only allows small liquid particles to pass through, the filtrate, and solid particles are remained as residue
What is crystallisation?
• Used to separate dissolved solid from solution • Solution heated, solvent evaporated, saturated solution left behind • Cool solution slowly and crystals begin to grow • Filtered than washed with cold distilled water to remove impurities