C2.1.3 - Pure And Impure Substances Flashcards Preview

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Flashcards in C2.1.3 - Pure And Impure Substances Deck (11):
1

What does a pure substance consist of?

Just 1 element or compound

2

Are mixtures pure or impure?

Impure

3

Why are mixtures impure?

The consist of more than 1 element or compound

4

Why is it difficult to obtain pure substances?

Because just 1 atom is needed to make a pure substance impure

5

What is an alloy?

An alloy is a mixture of a metal with 1 or more other elements

6

What is a melting point?

The temperature at which a substance changes from the solid state to a liquid state

7

What is the melting point of a pure substance measured in?

A single temperature

8

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

9

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

10

What is it important to do when determining a melting point?

Heat the substance slowly
Stir the substance as it melts

11

What does stirring the substance ensure?

That the entire sample is at the same temperature