Chemistry (paper 2) 📍 Flashcards
What are group 1 elements called?
Alkali metals
What are group 7 elements called?
Halogens
What are group 0 elements called?
Noble gases
Inert meaning
Unreactive
Noble gas characteristics
• Exist as single atoms
• Have a full outer shell = stable arrangement of electrons
• Therefore they’re inert and don’t easily form molecules
• Non - flammable
What is helium used for and why?
• Useful for airships
• Has a very low density and is non-flammable
What is neon used for and why?
• Useful for making illuminated signs
• Neon produces red/orange light when electricity is passed through it
What is argon used for and why?
• Used when an inert atmosphere is needed as it won’t react with anything
• Eg Argon is used to replace oxygen so that the oxygen doesn’t react with (or corrode) reactive metals being made
Alkali metal properties
• They’re reactive
• They’re soft
• They have low melting and boiling points
How do alkali metals react with water?
• They react with water to produce a metal hydroxide (alkali) and hydrogen
• Metal floats on surface as its less dense than water
• Metal fizzes as hydrogen gas is given off
• Universal Indicator goes blue/purple (pH 14) as alkaline metal hydroxide is formed
General equation for metal reacting with water
metal + water —> metal hydroxide + hydrogen
What happens to reactivity as you go down group 1 and how is it shown?
• The reactivity increases
• The amount of fizzing increases
• The reaction is more vigorous
Why do alkalis get more reactive as you go down group 1?
• As you go down the group there is a greater distance between the nucleus and outer electron
• Therefore there is less electrostatic attraction and the electron is more easily lost
Halogen charactersistics
• Exist as molecules made of pairs of atoms
• As you go down the group, the size of the molecules increases
• Therefore the melting and boiling point increases
Test for chlorine gas
When damp, blue litmus paper gets bleached white
General equation for metal reacting with halogen
halogen + metal —> metal halide
As you go down group 7 what happens to reactivity?
It decreases
Why do halogens get less reactive as you go down group 7?
• The greater distance between the nucleus and the incoming electron, the weaker the electrostatic attraction
• Therefore electrons are less easily gained
General equation for hydrogen reacting with halogen
hydrogen + halogen —> hydrogen halide
What do hydrogen halides form when dissolved in water?
Acidic solutions (eg HCL)
As you go down group 7, what happens to melting/boiling point and why?
• It increases
• The size of the molecules increases
Appearance of chlorine
Green gas
Appearance of bromine
Brown liquid
Appearance of iodine
Purple/black solid
Explain how hydrogen fluoride can form an acidic aqueous solution and name the acid
• Hydrofluoric acid is formed
• Hydrogen fluoride separates into 2 ions (H+ and F -) as it dissolves in water
• H+ ions make it an acid
What happens in halogen displacement reactions?
A more reactive halogen will displace a less reactive halogen from an ionic compound
Colour of chlorine in aqueous solution
Pale green
Colour of bromine in aqueous solution
Yellow
Colour of iodine in aqueous solution
Brown
[Topic 9]
Composite material meaning
Material made from two or more materials with different properties
Matrix meaning
The substance that binds fibres of the other material
Reinforcement meaning
Fibres that you add to the matrix
Fibre meaning
Long thin strands
Nanoparticle meaning
Tiny particles between 1 and 1000 nm consisting of a few hundred atoms
What is 1 nm equal to in metres?
1 x 10 ^-9
Uses of nanoparticles
• Nano-medicine (tiny enough to deliver drugs around body eg fullerene)
• Sunscreen (prevent harmful UV radiation reaching skin)
• Electrical circuits (conduct electricity)
Risks of nanoparticles in sunscreen
• Could get into bloodstream
• May damage cells
• Long term effects unknown
What do the useful properties of nanoparticles depend on?
Their large surface area to volume ratios
Properties of glass ceramics
• High melting/boiling points
• Transparent
• Made by sand (SiO2)
• Very hard
• Not very strong
• Brittle
• Not a heat/electricity conductor
Properties of clay ceramics
• High melting/boiling points
• Made from wet clay
• Strong
• Hard
• Brittle
• Not a heat/electricity conductor
Properties of metal
• High melting/boiling points
• Shiny
• Strong
• Soft (pure) / Hard (alloy)
• Malleable when soft/pure
• Heat and electricity conductor
Properties of polymers
• Moderately high boiling/melting points
• Made from covalent bonds between atoms
• Strong
• Not heat/electricity conductor
[Topic 7]
What is an exothermic reaction?
Reaction where heat energy is released
What is an endothermic reaction?
Reaction where heat energy is absorbed
Activation energy meaning
Minimum energy needed for particles to react
What happens during an exothermic reaction?
• Products have less energy than reactants
• Reaction gives out heat energy to surroundings
• Temperature increases
What happens during an endothermic reaction?
• Products have more heat energy than reactants
• Reaction takes in heat energy from surroundings
• Temperature decreases
Overall heat change meaning
The difference between the energy used to break bonds and the energy released when making bonds
(Break - make)
What overall heat energy change do exothermic reactions have?
• Negative overall heat energy change
• Less energy is used breaking bonds than is released by making bonds
Units for energy change
+/- ___ kJ mol ^-1
The 4 factors that affect the rate of a reaction
• Temperature
• Concentration / pressure
• Surface area
• Catalysts
How does temperature affect the rate of reaction?
• Increasing temperature means the particles have more kinetic energy
• More particles will have the activation energy allowing for more frequent successful collisions
How does concentration/pressure affect the rate of reaction?
• Increasing concentration/pressure makes particles closer together
• So there’ll be more frequent successful collisions
How does surface area affect the rate of reaction?
• Increasing the SA:V means more particles are exposed
• So there’ll be more frequent successful collisions
How do catalysts affect the rate of reaction?
• Catalysts speed up chemical reactions without changing chemically or in mass
• They provide an alternative route with a lower activation energy
• More particles have the activation energy
• There’ll be more frequent successful collisions
When investigating pH change until neutralisation what alternative can be used instead of universal indicator and why?
• pH probe
• Increases accuracy
When investigating pH change until neutralisation what alternative can we use to using a measuring cylinder for the volume of acid?
• A volumetric pipette
• More accurate
