Chemical Reactions

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Mixtures and Compounds

The the compound of two elements has completely different properties than the products you started with.

Alloys and Electroplating

Pure metals:

the atoms of pure metals are in regular arrangement

if you apply force, these atoms easily slide ver each other

this is why metals can be bent or beaten into shape

Alloys:

because there are different sized atoms an alloy it is not as easy to push one row of atoms over another

this means that alloys will be harder and more difficult to bend than pure metals

Alloy Main metal Added elements Improved properties

solder lead tin lower melting point than lead

duralumin aluminum copper and magnesium lighter and stronger than aluminum

stainless steel iron carbon, chromium, nickel, etc stronger and more resistant to corrosion than iron

Chemical reactions

if you burn toast you cannot get your bread back because a chemical reaction has occurred

if you melt an ice lolly you can get it back because it was just a physical reaction

physical reaction

chemical reactions are irreversible (very hard)

Physical reactions=

no new substances formed

often easy to reverse

Chemical reactions=

new substances formed

difficult reverse - to turn products back to reactants

Signs of a chemical reaction=

colour change

gas given off

temperature change

change in consistency

smell change

disappearance of reactants

energy being given off (FIYAAAAHHHH)

precipitate forms

volume changes