7C Matter Flashcards
How are particles arranged in a solid?
Closely packed, in rows and columns
How do particles move in a solid?
They vibrate in fixed positions
How do particles move in a liquid?
They flow over each other
How are particles arranged in a liquid?
Loosely packed, randomly, not in rows or columns
How are particles arranged in a gas?
Spread very far apart
Why can gases be compressed?
There is lots of space between the particles
Why do we use a model to represent the three states of matter?
We cannot see particles so it makes it easier to understand
Describe one limitation of the particle model
In reality: particles are not always spherical; the forces between particles or the energy of the particles is not shown
What is a change of state?
When a material changes from one state to another, e.g. melting from a solid to a liquid
Why are changes of state described as physical changes?
They are reversible, nothing new is formed and there is no temperature change
What happens to the particles in a solid when it melts?
They gain energy and move around more
What is the difference between evaporating and boiling?
Evaporation occurs at the surface of a liquid. Boiling occurs throughout the liquid
What is the change of state where a liquid is cooled to form a solid?
Freezing
What happens to the forces between particles when a gas condenses?
Forces become stronger
What two conditions are needed for sublimation to occur?
High temperature and pressure
Why doesn’t the temperature of a material change during a change of state?
The energy is used to overcome the forces holding the particles together
Why can particles in gases and liquids move around?
More energy than in solids and weaker forces holding them in place
What is Brownian motion?
Random movement of particles
Define what a fluid is
A substance in which particles are able to move
What is pressure?
A force caused by the particles colliding with the walls of a container
Why does an increase in temperature cause an increase in pressure?
More energy, move around more, collide with walls of the container more often
Why does a decrease in the number of particles cause a decrease in pressure?
Fewer particles means fewer collisions with the walls of the container
Why does an increase in container volume cause a decrease in pressure?
More space for the particles to move around means that they are more likely to collide with the walls of the container
Why is it dangerous if the pressure of a contained gas increases too much?
It may explode
Define diffusion
The movement of particles from high concentration to low concentration
Why does diffusion not occur in solids?
The particles don’t move
What is a concentration gradient?
A difference in concentration between two areas
Define equilibrium
When particles are evenly spread
Why does increasing temperature make diffusion faster?
The particles have more energy,move faster and therefore spread out more quickly.
How does a low concentration gradient affect diffusion?
The lower the gradient the slower the particles will spread out
How does increasing the diffusion distance affect diffusion?
Increasing the distance means the particles need to travel further it therefore takes longer
Give an example of diffusion
Perfume/ air freshener spreading out
What is a pure substance?
A substance made up of only one type of element or compound
Give an example of a pure substance
Pure water, gold
How is the everyday definition of pure different to the scientific meaning?
In everyday language, pure means that nothing has been added to it to change it
What is a mixture?
Contains two or more different substances which are not chemically joined
Give an example of a mixture
Orange juice, sea water, air
Why can mixtures be easily separated?
Yes as they are not chemically joined
How can mixtures of solids and liquids be separated?
Filtration, evaporation and distillation
Which technique is used to separate the different coloured dyes in pen ink?
Chromatography
What is a separating technique?
A physical process which separates mixtures
When filtering a mixture, what is collected in the filter paper?
Insoluble solids
Why might distillation be used instead of evaporation when separating a mixture of salt and water?
Distillation is used if we want to separate the liquid from the mixture
What two changes of state occur during distillation?
Evaporation, condensation
What is a sieve?
A tray with very small holes to allow small solids to pass through but stop large solids passing through
How do you separate a mixture of multiple solids?
Use sieves with different sized holes
Why are the different dyes separated during chromatography?
Different sized dye particles are carried different distances up the paper
Why can’t a magnet be used to separate a mixture of copper and sand?
Neither copper nor sand is magnetic
What is a soluble substance?
A substance which dissolves
What is an insoluble substance?
A substance which does not dissolve
Define solution
A mixture of solute and solvent
What does a solution look like?
Clear, can be different colours
Give two examples of solvents
Water and ethanol
What is a suspension?
Insoluble solid suspended in a liquid
What do we mean when we say that a substance has a high solubility?
Lots of solute will dissolve in a certain volume of solvent
How can you speed up the rate that sugar dissolves in tea?
Heat it, stir it, break it down into smaller pieces (increase surface area)
What is chromatography used to do?
Separate a mixture of soluble substances
What is the stationary phase?
The paper (which does not move)
What is the mobile phase?
The solvent (which does move)
State why the substances move different distances up the paper
The differentdissolvedsubstances in a mixture are attracted to the two phases in different proportions.
What will a pure substance look like on a chromatogram?
One spot
How does a chromatogram tell you how many substances are in a mixture?
Count how many spots there are
What will happen if the origin line is drawn in pen?
It will travel up the chromatography paper and interfere with the inks.
Why does the solvent level need to be below the origin line?
So the inks do not dissolve in the water
Name the three substances you are going to separate.
Sand, salt and iron filings
Why do you need to wear goggles and an apron?
To prevent anything getting on clothes or in eyes
In what order is each substance separated?
Iron filings, sand, salt
How do you prepare the filter paper for filtration?
Fold in half, fold in half again, separate one of the sides from the other three and open out into a cone
How will you evaporate the water from the evaporating basin?
Heat over a water bath
How do you know when to turn off the Bunsen burner?
When almost all of the water has evaporated
