The smart way to improve grades

Comprehensive & curriculum aligned

Affordable pricing from £10/month

Understand Pure Substances and Formulations

Worksheet Overview

QUESTION 1 of 10

When chemists talk about something being "pure", they don't mean that it is (necessarily) natural, or (necessarily) healthy. So what do they mean? And what's the opposite of pure?

In chemistry, a pure substance is one where all the particles are chemically the same. This might be a pure element (all the atoms are the same);

In this picture, the circles represent atoms; all the atoms are the same, so the box contains a pure element.

We could also have a pure compound, where different atoms are joined together to make compounds with a definite composition;

In this picture, each particle has a blue circle and a pink circle. They represent different atoms, but they are chemically linked, so each particle is the same.

In a mixture, not all particles are the same. The particle picture looks like this;

In this picture, the blue and pink atoms aren't chemically linked. Some of the particles are blue atoms and some are pink atoms. The other name for a mixture is a formulation.

How to tell if a substance is pure or a mixture

The easiest way to tell a pure substance from a mixture is to melt it. Pure substances- whether they are elements or compounds- will melt at a single temperature. In a mixture, each component will melt at a different temperature, leading to gradual melting over a range of temperatures.

Alloys

Alloys are mixtures based on metals; at least one of the elements in the mixture has to be a metal. Steel is an alloy of iron and carbon, brass is an alloy of copper and zinc. Pure metals tend to be quite weak, because they have flat layers in their structure which can slide over each other easily. Adding different atoms as a mixture disturbs these layers, so sliding can't happen as easily. This makes metal alloys are stronger and harder than pure metals. Some alloys have other useful properties, like being resistant to corrosion.

What does this picture show?

Pure element

Pure compound

Mixture

What does this picture show?

Pure element

Pure compound

Mixture

What does this picture show?

Pure element

Pure compound

Mixture

Match the phrases with their meanings.

Column A

Column B

Pure element
Different atoms, always combined in the same way
Pure compound
All the atoms are identical
Mixture
Different atoms, not chemically combined

What is the alternative name for a chemical mixture?

For each of these types of material, decide if it has a single melting temperature, or a range of melting temperatures.

 Single melting temperatureRange of melting temperatures
Pure element
Pure compound
Mixture
Formulation

Imagine doing an experiment where you melt two different substances. You get these results;

Substance Melting temperature (°C)
A 56
B starts melting at 45, ends melting at 51

Fill in the gaps in the sentence below.

 Single melting temperatureRange of melting temperatures
Pure element
Pure compound
Mixture
Formulation

Which of these is the best description of an alloy?

A compound containing several metals

A compound of a metal and a non-metal

A mixture of more than one metal

A mixture of a metal and another element or elements

 

 

Column A

Column B

Pure metal
');" onmouseout="tooltip.hide();">
Alloy
');" onmouseout="tooltip.hide();">

Which of these are common benefits of alloys over pure metals?

Alloys are often stronger than pure metals

Alloys are often cheaper than pure metals

Alloys are often harder than pure metals

Alloys conduct electricity better than pure metals

  • Question 1

What does this picture show?

CORRECT ANSWER
Pure element
EDDIE SAYS
There is only one type of atom, so all particles are the same, so this is a pure element.
  • Question 2

What does this picture show?

CORRECT ANSWER
Pure compound
EDDIE SAYS
There are two types of atom, so this isn't a pure element. However, each particle has the same chemical composition, so it is a pure substance; a compound not an element.
  • Question 3

What does this picture show?

CORRECT ANSWER
Pure compound
EDDIE SAYS
There are two types of atom, so this isn\\\'t a pure element. However, each particle has the same chemical composition, so it is a pure substance; a compound not an element.
  • Question 4

Match the phrases with their meanings.

CORRECT ANSWER

Column A

Column B

Pure element
All the atoms are identical
Pure compound
Different atoms, always combined ...
Mixture
Different atoms, not chemically c...
EDDIE SAYS
Have another look at the pictures if you're not sure about this. The difference between pure elements, pure compounds and mixtures is really fundamental, so take time to get it clear in your head.
  • Question 5

What is the alternative name for a chemical mixture?

CORRECT ANSWER
formulation
EDDIE SAYS
Lots of chemical products are formulations- medicines, food, cosmetics, structural materials. The idea is that each part of the formulation does something useful
  • Question 6

For each of these types of material, decide if it has a single melting temperature, or a range of melting temperatures.

CORRECT ANSWER
 Single melting temperatureRange of melting temperatures
Pure element
Pure compound
Mixture
Formulation
EDDIE SAYS
A pure substance is the same everywhere, down to the atomic bonds, so it will all melt at the same temperature. A mixture (and a formulation's just another name for a mixture) is different in different places, so will melt over a range of temperatures.
  • Question 7

Imagine doing an experiment where you melt two different substances. You get these results;

Substance Melting temperature (°C)
A 56
B starts melting at 45, ends melting at 51

Fill in the gaps in the sentence below.

CORRECT ANSWER
EDDIE SAYS
Substance A has a single melting temperature, so it is pure. We can't tell if it is an element or a compound. Substance B melts over a range of temperatures, so it is a formulation (or a mixture).
  • Question 8

Which of these is the best description of an alloy?

CORRECT ANSWER
A mixture of a metal and another element or elements
EDDIE SAYS
Alloys are mixtures. The main element in them is a metal, but the other elements can be metals (brass = copper + zinc) or non-metals (steel = iron + carbon).
  • Question 9

 

 

CORRECT ANSWER

Column A

Column B

Pure metal
');" onmouseout="tooltip.hide();">
Alloy
');" onmouseout="tooltip.hide();">
-->
EDDIE SAYS
In a pure metal, all the atoms are the same. In an alloy, some of the atoms are different. Can you see the straight lines in the pure metal structure, and how the large grey atom disturbs them in the alloy?
  • Question 10

Which of these are common benefits of alloys over pure metals?

CORRECT ANSWER
Alloys are often stronger than pure metals
Alloys are often harder than pure metals
EDDIE SAYS
The biggest benefits of alloying metals is that it improves their hardness and strength. Some alloys are less likely to corrode than pure metals- for example, stainless steel is an alloy.
---- OR ----

Sign up for a £1 trial so you can track and measure your child's progress on this activity.

What is EdPlace?

We're your National Curriculum aligned online education content provider helping each child succeed in English, maths and science from year 1 to GCSE. With an EdPlace account you’ll be able to track and measure progress, helping each child achieve their best. We build confidence and attainment by personalising each child’s learning at a level that suits them.

Get started
laptop

Start your £1 trial today.
Subscribe from £10/month.

  • educational
  • bettfutures
  • cxa
  • pta
  • era2016
  • BDA award
  • Explore LearningTuition Partner
  • tacm