Topic 2 - States of matter & mixtures Flashcards
what theory attempts to explain the 3 states of matter?
Particle theory/ kinetic theory
What are the 3 main assumptions of the particle theory?
That particles are small, inelastic and spherical
What are the particles like in a solid?
They are held in place by strong attractive forces so that they can only vibrate in position
What happens when a solid is heated?
The particles gain energy and vibrate faster and faster. Eventually they gain so much energy that they overcome the forces holding them together and the substance melts into a liquid
Why does heat cause particles in a solid to vibrate more?
Energy is transferred to the particles’ kinetic energy stores, causing them to vibrate faster
what happens when you heat a liquid?
The particles gain kinetic energy and move faster and faster. With enough energy they can break the forces of attraction between the molecules. At this point the liquid would boil into a gas
What happens when a gas is heated?
The particles gain energy and move faster and faster
What happens if you heat a gas that is inside a container that cannot expand?
If it cannot expand, it means the volume of the gas is fixed and so the pressure inside the container increases
What is condensation and how does it occur?
Condensation is when a gas turns into a liquid. This happens by the temperature of the gas being lowered until the particles are no longer able to overcome the forces of attraction between them, forcing them closer together and into a liquid
What is the melting point?
The temperature at which particles in a solid gain enough energy to break the forces of attraction between them and become a liquid
What is the boiling point?
the temperature at which particles in a liquid gain enough energy to break the forces of attraction between them and become a gas
What happens if you heat gas in a container that can expand?
The pressure is fixed so the volume will increase
in a closed system, why do changes of state not affect the mass?
because the amount of particles remains the same
Order the 3 states from lowest to highest density?
Lowest: gas
Middle: liquid
Highest: solid
What is chemical analysis (also known as analytical chemistry) about?
The instruments and methods we use to separate, quantify and identify different substances
What is a pure substance?
a single element or compound that hasn’t been mixed with any other substances
What are the melting and boiling points of pure water?
Melting point: 0 degrees
Boiling point; 100 degrees
How could you test an unknown liquid to test if it was water?
Heat it to 100 degrees and see if it boils or freeze it to 0 degrees to see if it freezes
What do we call the state change from solid to liquid?
Melting
What do we call the state change from a solid to a gas?
Sublimation
What do we call the state change from a liquid to a gas?
Evaporation
What do we call the state change from a liquid to a solid?
Freezing
What do we call the state change from a gas to a liquid?
Condensation
What do we call the state change from a gas to a solid?
Deposition
How can we tell if a substance is impure?
if you heat it and it starts melting at a certain temperature but doesn’t completely until you reach a higher one
What are formulations?
Mixtures that have been prepared using a specific formula
What are formulations made from?
formulations are made from precise amounts of different components that each have a different function
List 3 things that would require formulations?
Paint, cleaning agents and medicine
List 4 separation techniques?
Distillation, filtration, crystallisation and chromatography
Is testing for purity by measuring boiling point a chemical test?
It is a physical test
Outline the steps of simple distillation
heat a solution with a Bunsen burner, the liquid will evaporate into a gas that will rise into a water jacket and be condensed into a liquid which then flows into a beaker
List all the components needed for simple distillation
Boiling flask, fractionating column, condenser, cooling jacket and a beaker
What is simple distillation used for?
To separate a solvent from a solution
What is fractional distillation used for?
To separate different liquids within a mixture based on their varying boiling points
What is the difference between simple and fractional distillation?
Simple distillation can only be used on single substances, whereas fractional distillation can be used on multiple liquids within a solution
Describe the process of fractional distillation for 3 liquids?
Heat is applied and the liquid with the lowest boiling point evaporates and condenses into a beaker, if other liquids evaporate by chance , they condense in the fractionating column back into the flask. The temperature is altered to repeat the process for the 2nd liquid. the 3 liquids are separated based on different boiling points with the 3rd remaining in the flask
How would you separate salt water from pure water?
Simple distillation
What is a solvent?
A liquid in which substance can dissolve
What does soluble mean?
If something is soluble, it can dissolve in a liquid
What does insoluble mean?
If something is insoluble, it cannot dissolve in a liquid
When shouldn’t you use filtration?
When you are trying to separate a soluble solution from a solvent
What should you use when trying to separate a soluble substance from a solvent?
Evaporation
What should you use when trying to separate an insoluble substance from a solvent?
Filtration
Outline the process of crystalisation
first, pour the solution into an evaporating dish and heat it using a water bath. Stop heating it when crystals start to form and allow it to cool down. either leave it to allow the rest of the water to evaporate or filter out the crystals using aw filter paper and funnel. Dry the crystals
What is the “point of crystallisation”?
when crystals start to form
What is chromatography?
A chemical analysis technique used to separate substances in a mixture
What is the pencil line called in paper chromatography?
The baseline
Why is a pencil used for the baseline and not a pen?
The pen ink would dissolve in the solvent and move up the paper, affecting the results
Should the baseline be submerged in the solvent in paper chromatography?
NO
What are 2 solvents that are commonly used in paper chromatography?
Ethanol and water
What will happen to the insoluble parts of the ink in paper chromatography?
They will stay on the baseline
What is the name of the paper at the end of the paper chromatography?
A chromatogram
What is the mobile phase referring to?
The molecules that can move
What is the mobile phase in paper chromatography?
The solvent
What happens to a substance which is more soluble in the mobile phase?
It will spend more time in the mobile. This means it will move faster and further up the paper
What is the stationary phase referring to?
The molecules that cannot move
What is the stationary phase in paper chromatography?
The paper
What happens to a substance that is less soluble in the mobile phase?
It will spend more time in the stationary phase and will move slower and not very far up the paper
What is the formula for the Rf value?
distance travelled by the substance/distance travelled by the solvent
What happens if you change the mobile or stationary phase in paper chromatography?
You will get a different Rf value because the Rf value is specific to the mobile and stationary phases
What type of waste is nutrient run-off from fields?
Agricultural waste
What type of waste is used shower water?
Domestic waste
What type of waste is chemicals released from manufacturing factories?
Industrial waste
What happens before we return waster water to the environment?
We process it
Name 2 things removed from sewage and agricultural waste water before it is returned to the environment?
Organic matter and harmful microbes
What are the different steps for the treatment of water?
Screening, sedimentation, aerobic digestion and anaerobic digestion
What happens in the screening step of the treatment of water?
The sewage is passed through gratings and meshes to remove anything large
What happens in the sedimentation step of the treatment of water?
The sewage is left to sit in a settlement tank, so that heavier particles settle at the bottom as sludge, while the lighter particles settle at the too as effluent
What happens in the aerobic digestion step of the treatment of water?
Air is pumped through the effluent to supply the bacteria with oxygen
What happens in the anaerobic digestion step of the treatment of water?
The sludge is sealed in a container to prevent the entry of air, which ensures anaerobic respiration
What gas does the the anaerobic respiration of the sludge in water treatment produce?
Methane
What is the leftover sludge in water treatment used for?
Fertiliser
What is potable water?
Water that is safe to drink
What are the 3 criteria for water to be considered potable?
Fairly low levels of dissolved substances, pH between 6.5 and 8.5 and no microorganisms
Where does the UK get most of its potable water from?
Fresh water sources
List 3 sources of fresh water
Aquifers, lakes and rivers
What is surface water?
Water that is exposed to air, lakes, rivers and reservoirs
What is ground water?
Water the is formed underground, aquifers
What are 2 benefits of fresh water?
it is replaced frequently and is easy to access
How do we treat fresh water?
First pass it through a wire mesh to filter out any large objects. Then pass it through a bed of sand and gravel to filter out smaller things. Then sterilise it through bubbling chlorine gas through it, ozone exposure or ultraviolet radiation
What is desalination?
The extraction of potable water from seawater
What is the main drawback of desalination?
It requires a lot of energy so is very expensive (and contributes to global warming)
What are the 2 main techniques used in desalination?
Reverse osmosis and simpledistillation
