Chemistry: Particles

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  • Created by: rihyah
  • Created on: 07-03-17 13:51
What are some evidence for particles in the lab?
Place a crystal of potassium manganate(VII) in a beaker of water. The colour spreads through the water. Why? First, particles leave the crystal – it dissolves. Then they mix among the water particles.
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Can you give another example?
Place an open gas jar of air upside down on an open gas jar containing a few drops of red-brown bromine. The colour spreads upwards because particles of bromine vapour mix among the particles of air.
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What is Diffusion?
In all those examples, particles mix by colliding with each other and bouncing off in all directions. This mixing process is called diffusion.
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Describe a Solid.
A solid has a fixed shape and a fixed volume. It does not flow. Think of all the solid things around you: their shapes and volumes do not change.
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Describe a Liquid.
A liquid flows easily. It has a fixed volume, but its shape changes. It takes the shape of the container you pour it into.
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Describe a Gas.
A gas does not have a fixed volume or shape. It spreads out to fill its container. It is much lighter than the same volume of solid or liquid.
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When does Ice change to water?
Ice slowly changes to water, when it is put in a warm place. This change is called melting. The thermometer shows 0 °C until all the ice has melted. So 0 °C is called its melting point.
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Can you give an example of evaporation?
When the water is heated its temperature rises, and some of it changes to water vapour. This change is called evaporation. The hotter the water gets, the more quickly it evaporates.
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How do you know if the water is boiling?
bubbles appear int the water. It is boiling. The water vapour shows up as steam. The thermometer stays at 100 °C while the water boils off. 100 °C is the boiling point of water
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Describe the particles in a solid.
The particles in a solid are arranged in a xed pattern or lattice. Strong forces hold them together. So they cannot leave their positions. The only movements they make are tiny vibrations to and fro.
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Describe the particles in a Liquid.
The particles in a liquid can move about and slide past each other. They are still close together, but not in a lattice. The forces that hold them together are weaker than in a solid.
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Describe the particles in a Gas.
The particles in a gas are far apart, and they move about very quickly. There are almost no forces holding them together. They collide with each other and bounce off in all directions.
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What happens at a melting point?
At the melting point, the particles vibrate so much that they break away from their positions.
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What happens at boiling?
When a liquid is heated, its particles get more energy and move faster. They bump into each other more often, and bounce further apart. This makes the liquid expand. At the boiling point, the particles get enough energy to overcome the forces between
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What happens at evaporating?
Some particles in a liquid have more energy than others. Even well below the boiling point, some have enough energy to escape and form a gas. This is called evaporation. It is why puddles of rain dry up in the sun.
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What is Gas Pressure?
The pressure of a gas is the force that the gas exerts on the walls of its container.
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What happens thats the same with all gases?
When you heat a gas in a closed container, its pressure increases.
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What else is the same?
When a gas is compressed into a smaller space, its pressure increases.
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explain why the pressure increases when you: – heat a gas
the particles take in heat energy and move even faster. They hit the walls more often, and with more force. So the gas pressure increases.
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explain why the pressure increases when you squeeze a gas into a smaller space?
Now the particles are in a smaller space – so they hit the walls more often. So the gas pressure increase
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Define a Mixture
a substance made by mixing other substances together
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Define a solute.
the substance being dissolved in a mixture or solution (solvent)
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Define a Solvent.
the liquid in which a solute is dissolved to form a solution.
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Define a Solution.
a liquid mixture in which the minor component (the solute) is uniformly distributed within the major component (the solvent).
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Define a aqueous Solution.
An aqueous solution is a solution in which the solvent is water.
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Three examples of Solvents are?
Water and ethanol and acetone.
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define a pure substance.
substances that are made of only one type of atom or molecule
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define impurity.
An unwanted substance, mixed with the substance you want,
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some examples on where purity is crucial.
medical drug, or a flavouring for food.
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What happens when a substance contains an impurity?
– its melting point falls and its boiling point rises – it melts and boils over a range of temperatures, not sharply.
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The more impurity there is:
– the bigger the change in melting and boiling points – the wider the temperature range over which melting and boiling ID check! ! occur.
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By filltering
For example, chalk is insoluble in water. So it is easy to separate by filtering. The chalk is trapped in the filter paper, while the water passes through. The trapped solid is called the residue. The water is the filtrate.
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By crystallisation
You can obtain many solids from their solutions by letting crystals form. The process is called crystallisation. It works because soluble solids tend to be less soluble at lower temperatures
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By evaporating all the solvent
For some substances, the solubility changes very little as the temperature falls. So crystallisation does not work for these. Salt is an example.
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Separating a mixture of two solids
To separate two solids, you could choose a solvent that will dissolve just one of them. For example, water dissolves salt but not sand. So you could separate a mixture of salt and sand like this: 1 Add water to the mixture, and stir. The salt dissolv
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how can you make use of paper chromatography?
 identify a substance  separate mixtures of substances  purify a substance, by separating it from its impurities.
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Other cards in this set

Card 2

Front

Can you give another example?

Back

Place an open gas jar of air upside down on an open gas jar containing a few drops of red-brown bromine. The colour spreads upwards because particles of bromine vapour mix among the particles of air.

Card 3

Front

What is Diffusion?

Back

Preview of the front of card 3

Card 4

Front

Describe a Solid.

Back

Preview of the front of card 4

Card 5

Front

Describe a Liquid.

Back

Preview of the front of card 5
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