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Name the three states of matter, and the physical changes that occur between them.
Solids – relatively rigid, definite volume and shape. In a solid, the atoms and molecules are attached to each other.
Liquids – definite volume but able to change shape by flowing. In a liquid, the atoms and molecules are loosely bonded.
Gases – no definite volume or shape.
Describe the arrangements and movement of particles in the different states of matter
The particles in solids vibrate about fixed positions; even at very low temperatures. Individual particles in liquids and gases have no fixed positions and move chaotically.
Use information to predict the state of a substance
You can predict the state of a substance at a given temperature if you know its melting point and boiling point.
Describe the relative energies of particles in the different states of matter
gas particles have the most energy, solid particles have the least energy and liquid particles are somewhere in between.
Explain why the movement and arrangement of particles change during changes of state
because the energy is being used to form or break particle bonds and doing this changes the particle arrangement and therefor their movement.
Explain why the energy of particles changes during changes of state
energy is either added or removed from a substance, affecting the way the particles interact with each other.
Describe the differences between a pure substance and a mixture
A mixture is a physical combination of two or more pure substances in which each substance retains its own chemical identity. A pure substance is a single substance on its own.
Use melting point information to decide whether a substance is pure or is a mixture
Pure substances can be identified by comparing the melting point found in the experiment with published reference data of what the melting point should be.
Describe what happens to atoms at a pure substances melting point
the atoms will have a constant appearance, colour and density.
Interpret a heating curve to identify a melting point
The temperature at which the melting phase takes place is called the melting point.
Explain why the temperature does not change as a pure substance melts
energy goes exclusively to changing the phase of a substance; it does not go into changing the temperature of a substance.
State some mixtures that can be separated by filtration
sand and water, dirt and water, etc.
State some mixtures that can be separated by crystallisation
salt and ammonium chloride
Draw and interpret diagrams showing how filtration and crystallisation are done
Explain the formation of crystals during crystallisation
As the solution cools, the solvent can no longer hold all of the solute molecules, and they begin to leave the solution and form solid crystals.
Explain how mixtures are separated by filtration
using a funnel lined with filter paper to retain the solids while letting the liquid through.
Explain ways of reducing risk when separating mixtures by filtration and crystallisation
During crystallisation, the risks from spitting can be reduced by wearing eye protection, removing the Bunsen burner before the solution is completely dry and/ or using steamroll heat the evaporating basin gently.
Describe how some mixtures can be separated by chromatography
Identify pure substances and mixtures on chromatograms
Identify substances that are identical on chromatograms
Draw and interpret diagrams showing how chromatography is done
Explain how substances can be separated by chromatography
