Unit 17, 18 & 19 - Groups in the Periodic Table/ Rates of Reaction/ Heat Energy Changes in Chemical Reactions Flashcards
What and the group 1 elements called
Alkali metals
Give 2 properties of alkali metals that are different to normal metals
Low melting points, soft and easy to cut
What happens to alkali metals when they are burned in air
They are oxidised
Which way does the reactivity of alkali metals go?
More reactive further down
Why are alkali metals with more shells more reactive
It is easier for the electron to be lost
What are group 7 elements called
Halogens
What type of molecules do halogens exist as
Diatomic
Why do halogens need to be handled with care
They are toxic and corrosive
What does chlorine look like
A green has
What does iodine look like
Purple/ black solid
What does bromine look like
Brown liquid
What is formed when a halogen reacts with metals
Salts with halide ions
Give a halide salt and what it is used for
Sodium chloride, table salt
Why can all halogens be used as disinfectants and bleaches
They kill microorganisms and remove colour
What is the test for chlorine
Turns damp blue litmus paper red then bleached
What is formed when halogens react with hydrogen
Hydrogen halides which form an acid
How is HCl acid made
Hydrogen gas and chlorine gas react to form hydrogen chloride, when dissolved in water, the ions disassociate so the H+ ions make it an acid
Which way are the halogens more reactive
As you go up the table
How can the order of halogens be worked out
Using displacement reactions
Why do halogens with less shells react more
It is easier to gain an electron
What is a redox reaction
When a reaction has oxidation and reduction
What are group 0 elements called
Noble gases
Give 3 properties of noble gases
Colourless
Low melting points
Poor conductors
What is a unique property of noble gases
Inert, don’t react easily
Why do noble gases all exist as single atoms
Don’t form bonds easily
What is krypton used for
Photography lighting because it produces a white light when electricity passes through it
What is argon used for
Stops oxygen reacting with wine between cork and wine as it is dense than air
What is helium used for
Weather balloons as it has a low density and is non flammable
What is neon used for
Making illuminated signs as it produces red-orange light when electricity is passed through it
Why are noble gases inter
They have full outer shells
What is the rate of reaction?
The speed at which reactants are turns into products
How can we control the rates of reaction
By altering variables
Why do granules of magnesium react faster than a ribbon
Their surface area is bigger
What is the activation energy
The minimum amount of energy needed for a reaction to occur
What is an exothermic reaction
A reaction which releases energy
What are endothermic reactions
Reactions where energy is taken in
Give an example of an endothermic reaction
Electrolysis of copper chloride
What 4 factors affect the rate of a reaction
Concentration, surface area, pressure of gases, temperature
Why does the concentration affect the rate of reaction
When it increases, there are more particles so collisions occur more often
How does surface area affect the rate of reaction
If it increases, the rate increases as there is more surface for collisions
How does pressure of gases affect the rate of a reaction
Increased pressure means the particles are closer together so collide more
How does temperature affect the rate of a reaction
Increased temperature means they particles move faster so collide more often
Explain the core practical - Investigating reaction rates, measuring volumes of gases
Set up conical flask with bung and delivery tube
Attach the delivery tube to a set up for measuring gas
Add 40cm3 of hcl and 5g of marble chips to the conical flask
Note how much gas is produced every 30 seconds
Repeat with larger marble chips
Explain the core practical - Investigating reaction rates, observing colour change
Place 50cm3 of sodium thiosulphate solution into a conical flask
Measure 5cm3 of dilute hcl in a test tube
Place both the conical flask and test tube in a water bath and note down temperature
After 5 mins, remove and place flask on paper with a cross drawn
Add acid and measure how long it takes for cross to disappear
Repeat with different temperatures
What are catalysts
Substances that speed up chemical reactions without being permanently changed
What catalyst is used in the manufacture of nitric acid from ammonia
Platinum
Why don’t catalysts need to be replaced
They don’t get used up
How do catalysts save costs
They allow reactions to occur at lower temperatures
How does a catalyst make a reaction faster
The activation energy is lower so more molecules have enough energy to react
What are enzymes
Biological catalysts made from proteins
What is the active site
The specific shape in an enzyme where the substrate fits into
What is the enzyme for alcoholic drinks
Yeast
What does a reaction model show
The energy change during a chemical reaction
How can you determine whether a reaction in a solution is exothermic or endothermic?
If it is exothermic, the temperature increases in the solution
Which 2 types of reactions are always exothermic?
Neutralisation and displacement
Give a type of reaction that has a low activation energy
Precipitation
What yep of reaction has a high activation energy
Combustion
What is bond energy
The average energy needed to break once mole of a particular bond
Which part of a reaction is exothermic
Making the bonds
Which part of a reaction is endothermic
Breaking the bonds
How do you calculate energy change
Energy change = energy in - energy out
What is bond energy measured in
KJ/ mol
