Chemistry (paper 2) 📍 Flashcards by O C

What are group 1 elements called?

Alkali metals

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What are group 7 elements called?

Halogens

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What are group 0 elements called?

Noble gases

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Inert meaning

Unreactive

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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

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What is helium used for and why?

• Useful for airships
• Has a very low density and is non-flammable

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What is neon used for and why?

• Useful for making illuminated signs
• Neon produces red/orange light when electricity is passed through it

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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

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Alkali metal properties

• They’re reactive
• They’re soft
• They have low melting and boiling points

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How do alkali metals react with water?

• It would dissolve
• It can ignite (depends on reactivity)
• Metal fizzes as hydrogen gas is given off

• Universal Indicator goes blue/purple (pH 14) as alkaline metal hydroxide is formed

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General equation for metal reacting with water

metal + water —> metal hydroxide + hydrogen

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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

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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

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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

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Test for chlorine gas

When damp, blue litmus paper gets bleached white

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General equation for metal reacting with halogen

halogen + metal —> metal halide

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As you go down group 7 what happens to reactivity?

It decreases

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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

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General equation for hydrogen reacting with halogen

hydrogen + halogen —> hydrogen halide

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What do hydrogen halides form when dissolved in water?

Acidic solutions (eg HCL)

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As you go down group 7, what happens to melting/boiling point and why?

• It increases
• The size of the molecules increases

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Appearance of chlorine

Green gas

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Appearance of bromine

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Brown liquid

Appearance of iodine

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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 • And so could catalyse reactions in the body • 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 • Breaking bonds needs energy • Forming bonds releases energy • More energy is given out than taken in

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

Chemistry (paper 2) 📍 Flashcards

(57 cards)