chemistry revision Flashcards
what is an element?
elements are pure substances made from only one type of atom
what is a compound?
compounds are pure substances made of two or more elements that are chemically joined together
what are mixtures?
mixtures are 2 pure substances mixed together, but not chemically joined
what is an alloy?
an alloy is a mixture of two or more elements, one of which is metal. Alloys often have properties that are different to the metals they contain. This makes them more useful than the pure metal alone.
four signs of chemical changes
colour change
energy change - heat, light or even sound may be given out
gas given off (formation of bubbles)
precipitate forms (a cloudy solid appears in a solution)
what is a chemical reaction?
A chemical reaction is a change, which forms new substance(s)
what is a physical change?
In a physical change appearance or form changes, but no new substances are made
what is a word equation?
When a chemical reaction takes place, we can use an equation to make a summary of what happened. A chemical equation tells you which substances we started with (the reactants) and the new substance(s) that were made in the reaction (the products)
how do you write a word equation?
reactant + reactant -> product
what happens when an acid is neutralised?
when acid is neutralised, one of the products is always a salt.
how can you tell what metals are the most reactive?
they end in “ium”
how can you tell what metals are the least reactive?
the least reactive metals are the expensive metals used in jewellery
what is the scientific name for combustion?
Burning
what is always one of the reactants for combustion?
oxygen
what is in the combustion triangle?
Heat
Fuel
Oxygen
