States of Matter and Particle Theory
Define matter in one sentence.
Matter is anything that has mass and takes up space.
Name the change of state when a liquid turns into a solid.
This change of state is called freezing.
Define a pure substance.
A pure substance is made up of only one type of particle, either an element or a compound.
Define solute and solvent.
A solute is the substance that is dissolved, and a solvent is the substance that does the dissolving.
Name one separation technique used to remove sand from water.
Decantation can be used to separate sand from water.
Describe how particles are arranged in a solid compared to a liquid.
In a solid, particles are tightly packed in fixed positions. In a liquid, particles are close together but can slide past each other. The difference between a solid and a liquid is that the particles in a liquid have more room to move whereas the particles in a solid are too tightly packed to move.
Explain why ice melts when heated using particle theory.
When ice is heated, the particles gain more energy and vibrate faster, which weakens the bonds holding them in place. This allows the solid to change into a liquid.
Give one example of a homogeneous mixture and explain why it is classified as such.
Salt water is a homogeneous mixture because the salt particles are spread evenly through the water, making it look the same throughout.
Explain why sugar seems to “disappear” when stirred into hot tea.
Sugar does not disappear, it dissolves. The sugar particles spread out evenly between the water particles, forming a solution.
Explain why magnets can separate iron filings from sand.
Magnets attract magnetic substances like iron, so the iron filings can be pulled out while the sand is left behind.
Explain why gases are easy to compress but solids are not.
Gases can be compressed because their particles are far apart, leaving empty space that can be squeezed. Solids cannot be compressed because their particles are tightly packed with no space between them.
Why does the temperature of boiling water stay at 100 °C until it all turns into steam?
At boiling, the heat energy is used to change water from liquid to gas, not to increase the temperature. This is why the temperature stays at 100 °C while the water evaporates.
Explain the difference between a compound and a mixture, with examples.
A compound is made of two or more elements chemically combined, like water (H₂O). A mixture is made of substances physically combined, like sand and water, which can be separated.
Why does sugar dissolve faster in hot water than cold water? Use particle theory.
In hot water, particles move faster and collide more strongly with sugar particles, breaking them apart more quickly. In cold water, particles move slowly, so dissolving takes longer.
Compare filtration and sieving, describing what they separate and why.
Filtration separates small insoluble solids from liquids using filter paper, like sand from water. Sieving separates larger particles from smaller ones using holes in a sieve, like flour and rice.
State and explain one rule from the particle theory, giving an example.
One rule is that particles are always moving. This can be seen in gases, where particles move quickly in all directions, which is why gas spreads out to fill its container.
Explain condensation using particle theory, with an example.
Condensation happens when gas particles lose energy and move closer together to form a liquid. For example, water vapour in the air cools on a cold glass and forms liquid droplets.
Justify why air is classified as a mixture, not a pure substance.
Air is a mixture because it contains different gases like oxygen, nitrogen, and carbon dioxide that are not chemically bonded. The amounts of these gases can also change, such as in humid or polluted air.
Define a saturated solution and describe how you would make one.
A saturated solution is one where no more solute can dissolve at a given temperature. You can make one by adding sugar to water until it stops dissolving and settles at the bottom.
Describe how chromatography works using an example such as ink.
Chromatography separates substances based on how well they dissolve and move through paper. For example, black ink can separate into different colours because the dyes travel at different speeds.
Compare the energy and movement of particles in solids, liquids, and gases, linking this to their physical properties.
In solids, particles have low energy and only vibrate, so solids keep their shape. In liquids, particles have more energy and slide past each other, so liquids flow but keep a fixed volume. In gases, particles have high energy and move freely, so gases spread out to fill any container.
Evaluate this statement: “Water particles disappear when water evaporates.” Write the correct scientific explanation.
The statement is incorrect. Water particles do not disappear, they change state from liquid to gas. The particles spread out in the air, which is why we cannot see them.
Compare homogeneous and heterogeneous mixtures, linking particle arrangement and appearance.
In a homogeneous mixture, particles are evenly spread so it looks the same throughout, like salt water. In a heterogeneous mixture, particles are unevenly spread and different parts can be seen, like oil and water.
Explain the difference between dilute, concentrated, and supersaturated solutions with examples.
A dilute solution has only a little solute, like weak cordial. A concentrated solution has a lot of solute, like strong cordial. A supersaturated solution has more solute than normal, which can happen by heating the solvent and then cooling it, like rock candy.
Justify which method (filtration or dissolving then filtration) is more effective for separating a sand–salt mixture, and explain why.
Dissolving then filtration is more effective. This is because the salt dissolves in water and passes through the filter, while the sand stays behind. The salt can then be recovered by evaporation.