C2.1.3 - Pure and Impure Substances Flashcards
What does a pure substance consist of?
Just 1 element or compound
Are mixtures pure or impure?
Impure
Why are mixtures impure?
The consist of more than 1 element or compound
Why is it difficult to obtain pure substances?
Because just 1 atom is needed to make a pure substance impure
What is an alloy?
An alloy is a mixture of a metal with 1 or more other elements
What is a melting point?
The temperature at which a substance changes from the solid state to a liquid state
What is the melting point of a pure substance measured in?
A single temperature
What features do melting points of impure substances tend to have?
Melting over a range of temperatures.
The melting point is lower than of a pure substance
How do you determine a melting point?
By heating the substance, and then either by measuring the temperature at which it melts, or measuring its temperature at regular time intervals and plot a graph
What is it important to do when determining a melting point?
Heat the substance slowly
Stir the substance as it melts
What does stirring the substance ensure?
That the entire sample is at the same temperature
