States of Matter Flashcards
What does the particle model do?`
Explains state changes in a substance in terms of the arrangement, movement and energy stored in its particles
Describe the arrangement of particles in a gas, liquid and solid
Gas - random and far apart
Liquid - random and close together
Solid - regular and close together
Describe the movement of particles of the 3 states of matter
Gas - fast in all directions
Liquid - move around each other
Solid - vibrate about fixed positions
State changes are physical changes. What does this mean?
They can be reversed and the chemical properties of the substance don’t change
What do state changes change?
The particles’ arrangement, their movement and the amount of stored energy
What is sublimation?
From solid to gas
What is deposition?
From gas to solid
With what information can you predict the state of a substance?
If you know its melting point, boiling point and temperature
If a substance is below its melting point, what state is it in?
The solid state
If a substance is between the melting and boiling point, what state is it in?
The liquid state
If a substance is above the boiling point, what state is it in?
The gas state
Can the composition of a pure substance be changed?
No and it is the same in all parts of a piece of the substance
What is a mixture?
A substance that contains elements and/or compounds that are not chemically joined together
Why can’t we separate pure substances using physical methods like filtering or picking bits out?
Because it has the same fixed composition in all its parts
Why can you use physical methods to separate a mixture?
Because it does not have a fixed composition
What happens when a solid melts?
Its particles gain enough energy to overcome the weak forces of attraction between them
Give an example of a phyiscal poroperty
Melting point
What is a solution?
A mixture made up of solutes in a liquid called the solvent
What is a solute?
Dissolved substance
What is crystallisation?
When solutes are separated by evaporating the solvent to leave the solutes behind
What is a saturated solution?
A solution that contains the maximum amount of solute that can dissolve in that amount of solvent at that temperature
What is the filtrate?
The solvent and solute (s) that pass through the fine holes in the filter paper
What is the residue?
The bits of insoluble substances that can’t fit through the filter paper holes
What is a risk assessment?
Where the hazards of doing an experiment are identified
What is the use of chromatography?
To find out which coloured compounds a mixture contains
What is the solvent in paper chromatography called?
The mobile phase
What phase the paper in paper chromatography contain?
The stationary phase, through which the solvent and dissolved substances move
What is the name of the paper with the separated components on it called?
A chromatogram
What is the Rf value in paper chromatography?
The distance the compound has rises divided by the distance the solvent has risen
How do you calculate the Rf value?
Rf = Distance moved by the spot/Distance moved by the solvent
What can paper chromatography be used for?
-Distinguish between pure and impure substances
-Identify substances by comparing the pattern on the chromatogram with the patterns formed by known substances
Identify substances by calculating their Rf value
What is distillation?
The process of separating the components or substances from a liquid mixture by using selective boiling and condensation
What is the name of the apparatus used in distillation?
A still
What is fractional distillation?
A distillation process that separates 2 or more liquids
How can fractional distillation work>
Some liquids boil more easily than others due to their different boiling points, and so one will turn into vapour first
What is desalination?
Producing pure water from sea water
How does desalination work?
Using simple distillation - sea water is heated so that water vapour leaves it quickly. This vapour is then cooled and condensed, forming water without the dissolved salts
Why is simple distillation usually not a suitable method for producing large volumes of drinking water?
A lot of energy must be transferred to sea water for this to happen
What doe chemical analysis involve?
Using chemical reactions or sensitive machines to identify and measure the substances in a sample
What are aquifers?
Underground rocks containing groundwater
What are the 3 steps of water treatment?
Filtration, sedimentation and chlorination
Why is chlorination an important part of water treatment?
Because the chlorine kills the microorganisms in the treated water
What kind of melting points do pure substances have?`
Sharp melting points
What do mixtures melt over?
A range of temperatures - no sharp melting points
What is a pure substance?
Substance that contains only 1 element/compound
What happens when salt is added to water?
It lowers the freezing point and it weakens the rigid lattice structure and molecules are disordered
What does insolubke mean?
Doesn’t dissolve
How do you purify a liquid?
By removing solid impurities from it
Why does filtration work?
They have tiny pores that are:
- large enough to let water molecules/dissolved substances through
- small enough to stop insoluble solid particles getting through
What do you use crystallisation for?
To produce solution crystals from a solution
What is a saturated solution?
A solution that can’t hold any more solute
Why is a hot water bath preferred for crystallisation?
Gives you more control over heating than a Bunsen Burner flame directly on the evaporating dish
What is solubility?
The mass of a solute that dissolves in a given volume of a solvent at a given temperature
Why does crystallisation work?
- The solubility of the solute decreases as the saturated solution cools
- Crystals form from the excess solute
What happens when salt is added to water?
It lowers the freezing point and it weakens the rigid lattice structure and molecules are disordered
What does insolubke mean?
Doesn’t dissolve
How do you purify a liquid?
By removing solid impurities from it
Why do you use a lid in paper chromatography?
It stops evaporation of the solvent
What do you use crystallisation for?
To produce solution crystals from a solution
What is a saturated solution?
A solution that can’t hold any more solute
Why is a hot water bath preferred for crystallisation?
Gives you more control over heating than a Bunsen Burner flame directly on the evaporating dish
What is solubility?
The mass of a solute that dissolves in a given volume of a solvent at a given temperature
Why does crystallisation work?
- The solubility of the solute decreases as the saturated solution cools
- Crystals form from the excess solute
What is the stationary phase?
A substance that does not move (the chromatography paper)
What is the mobile phase?
A substance that moves through the stationary phase (the solvent)
What happens during chromatography?
Each soluble substance in the mixture forms bonds with the two phases, but if it moves or not depends on which bonds are stronger:
- Stationary phase - stay near bottom of paper
- Mobile phase - move towards the top
Why do you use a lid in paper chromatography?
It stops evaporation of the solvent
What can you use a chromatogram for?
- Distinguish between pure and impure substances
- Identify a substance by company of pattern of spots with those of a known substance
- Identify substances using Rf values
Are soluble compounds carried up the paper faster or slower?
Faster than less soluble ones, so the compounds separate out
How do you make pure water?
Using distillation - separating it from dissolved solids
Why does distillation work?
When the mineral water evaporates, only the water turns to gas (vapour) and so it leaves the solid minerals with much higher boiling points behind. The pure vapour is then condensed, making a pure liquid
In distillation, what is a condenser?
A central tube surrounded by a jacket of cold water. It keeps the tube cool, so that almost all of the vapour condenses and turns into a liquid
What do anti-bumping granules do?
Make the liquid boil more smoothly; small bubbles of vapour form on the corners of the granules and reduce the risk of the liquid boiling over
What is fractional distillation and why does it work?
The separation of a mixture into its component parts; some liquids boil more easily than others and will turn into vapour first
What are the 3 stages of water treatment in order?
Sedimentation - large insoluble particles (like stone) sink to the bottom of the tank
Filtration - small insoluble particles are removed by filtering through beds of sand (water can get through sand but small insoluble particles stay at the top)
Chlorination - chlorine gas is bubbled from the water to kill microbes
Give an advantage and disadvantage of simple distillation of sea water
Advantage - kills microbes in the sea water/produces pure water/uses plentiful raw materials
Disadvantage - needs a lot of energy to heat the water
Why does the temperature remain constant during melting?
It is an isothermal process, meaning the temperature remains constant. The energy goes directly into changing the phase and state of the substance as opposed to changing the temperature of the substance
