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C1 (Particles and mixtures (Molecule (A cluster of non-metal atoms that…
C1
Particles and mixtures
A solution is made when a solute, usually a soluble solid compound, is dissolved into a liquid called a solvent, typically water.
If the solute is coloured (eg blue copper sulfate) then the solution will have a colour. As with the white solute, the particles are now too small to see, and evenly spread out.
If the solute is white (eg sodium chloride) then the solution is colourless. This is because the individual particles (in this case, ions) in the sodium chloride crystals break apart and spread out through the water.
Atom
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Scientists originally thought that atoms could not be split up, but this is not the case.
Molecule
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The atoms always join in fixed ratios and molecules have a specific formula, eg H2O or N2.
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Element
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Most are metals, a few are semi-metals, and the rest are non-metals
Compound
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Elements bond in fixed ratios and so can be represented by a chemical formula. For example, sodium chloride has the same number of sodium ions and chloride ions, so its formula is NaCl; whereas water is always made from twice the number of hydrogen atoms as oxygen atoms, so it is H2O.
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Atomic number, mass number and isotopes
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Halogens
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Room temperature is usually taken as being 25°C. At this temperature, fluorine and chlorine are gases, bromine is a liquid, and iodine and astatine are solids. There is therefore a trend in state from gas to liquid to solid as you go down the group.
The halogens become darker as you go down the group. Fluorine is very pale yellow, chlorine is yellow-green, and bromine is red-brown. Iodine crystals are shiny purple - but easily turn into a dark purple vapour when they are warmed up.
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Alkali Metals
All the Group 1 elements are very reactive. They must be stored under oil to keep air and water away from them. Group 1 elements form alkaline solutions when they react with water, which is why they are called alkali metals.
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Periods and Groups
B, Si, As, Te, At zigline no further than them