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Explain Atoms, Elements, Compounds and Mixtures

In this worksheet, you will learn about atoms and the different ways of mixing and combining atoms to make substances.

Worksheet Overview

QUESTION 1 of 10

For thousands of years, people have wondered what things are made of. In Ancient Greece, people had the idea of atoms; tiny blocks which were so small they couldn't be broken into smaller pieces.

We now know that there are about 120 different types of atom and that everything around is made of different atoms joined together in different patterns. Atoms are a lot like toy blocks. You can use a few types of block to make all sorts of things, depending on how you join them together.

 

 

Each atom has a name and a symbol. You need to know the names and symbols for the first twenty. This looks scary, but if you test yourself on a few at a time, you will soon know them all by heart.

 

Names and symbols for the first twenty atoms

 

Hydrogen H Carbon C Sodium Na Sulfur S
Helium He Nitrogen N Magnesium Mg Chlorine Cl
Lithium Li Oxygen O Aluminium Al Argon Ar
Beryllium Be Fluorine F Silicon Si Potassium K
Boron B Neon Ne Phosphorus P Calcium Ca

 

The symbols are always either a capital letter or a capital letter followed by a lower case letter. Most of the symbols start with the same letter as the atom's name, but not all- can you see which atoms have symbols which don't match their name?

 

Because atoms are so small, we need to think about how to combine them to make things. There are three main ways of doing this:

In an element, all the atoms are the same type. In pure gold bars, all the atoms are gold atoms. When a scientist draws a picture of the atoms in a gold bar, all the atoms look the same.


Gold BarsAtomic structure of gold

 

In a compound, different atoms are joined together (chemists say "bonded"), but in fixed patterns. Water is a compound of hydrogen and oxygen, with two hydrogen atoms for each oxygen atom. In the atomic picture, the two white balls are hydrogen atoms, and the red ball is an oxygen atom.


Glass of water Atomic structure of water


Table salt is a compound of sodium and chlorine, with one sodium atom for each chlorine atom. In this atomic picture, purple means sodium and green means chlorine.


Atomic structure of sodium chloride

 

In a mixture, different elements or compounds are in the same container, but they are not bonded, and they have no pattern. Seawater contains water and dissolved salt, but they don't make a new compound, they are still water and salt.
 

 

If you have a mixture, you can usually separate it back into different pure elements and compounds. Some ways of separating a mixture are:

Filtration, using a sieve or filter paper. Liquids go through the filter, but solids get trapped.


 

Crystallisation, where we remove the liquid by heating it so that it evaporates; the solid gets left behind.

Simple distillation, where we heat a liquid so that it evaporates. We collect the vapour and cool it back down to collect a pure liquid.


 

Fractional distillation, which is like simple distillation, except that we carefully collect different liquids which condense at different temperatures.

Chromatography separates different substances dissolved in a solution, for example, different colours mixed together to make ink.

 

You will learn a lot more about these different methods in another activity. For now, the important thing to remember is that mixtures are easy to separate into pure elements or pure compounds. Converting a pure compound into separate pure elements is much harder because it means breaking chemical bonds.

Which of these phrases describes an atom best?  Select the two answers that when joined together give the perfect answer.

Which of these explains why atoms are like toy blocks?

Atoms have different colours and shapes.

Atoms are about as big as toy blocks.

Atoms are lumpy when we touch them.

We can make many different things by combining blocks in different patterns.

What are the symbols for these element names?  (Clue - make sure you use capital letters for this question!)

Atoms have different colours and shapes.

Atoms are about as big as toy blocks.

Atoms are lumpy when we touch them.

We can make many different things by combining blocks in different patterns.

Here are some different ways of writing the symbol for sodium. Pick out the right way, and the reason each of the others is wrong.

Column A

Column B

So
Not all element symbols are the first two letters ...
Na
This is the correct symbol.
NA
The first letter in they symbol needs to be a capi...
nA
Only one letter in the symbol is a capital letter.

What are the names of the elements with these symbols?

Column A

Column B

So
Not all element symbols are the first two letters ...
Na
This is the correct symbol.
NA
The first letter in they symbol needs to be a capi...
nA
Only one letter in the symbol is a capital letter.

Use these words to fill in the blanks:

 

Aluminium

Atom

Bonded

Element

Mixture

Pure

Column A

Column B

So
Not all element symbols are the first two letters ...
Na
This is the correct symbol.
NA
The first letter in they symbol needs to be a capi...
nA
Only one letter in the symbol is a capital letter.

Does this picture show an element, a compound or a mixture?

 

Element

Compound

Mixture

We can't be sure

Does this picture show an element, compound or mixture?

 

Element

Compound

Mixture

We can't be sure

How do you separate sand from water?

Which of these are separation methods? Put a cross the box for every separation method.

Filtration

Chromatography

Complex distillation

Picturing

Simple distillation

Evaporation

Molecular structuring

  • Question 1

Which of these phrases describes an atom best?  Select the two answers that when joined together give the perfect answer.

CORRECT ANSWER
EDDIE SAYS
If a question asks you to choose the best option, be very careful! There could be some answers which are sort-of true, but aren't as good as the right answer. There are about 120 types of atom, and the idea was invented in Ancient Greece, but neither of those answers describes what atoms are really like.
  • Question 2

Which of these explains why atoms are like toy blocks?

CORRECT ANSWER
We can make many different things by combining blocks in different patterns.
EDDIE SAYS
Thinking about atoms as like toy blocks helps us understand how a small number of atoms can make so many different things, but atoms don't really look like that. They are much much smaller- so small that they don't really have shape or colour at all. We pretend they do so that we can see pictures of them in our mind.
  • Question 3

What are the symbols for these element names?  (Clue - make sure you use capital letters for this question!)

CORRECT ANSWER
EDDIE SAYS
Once you have got these right, you know a quarter of the names and symbols you need. That's a good start! Don't worry if you need to do questions like this one a few times to get all the symbols learned.
  • Question 4

Here are some different ways of writing the symbol for sodium. Pick out the right way, and the reason each of the others is wrong.

CORRECT ANSWER

Column A

Column B

So
Not all element symbols are the f...
Na
This is the correct symbol.
NA
Only one letter in the symbol is ...
nA
The first letter in they symbol n...
EDDIE SAYS
It seems picky, but the capital letters rule is really important and useful. For compounds, you need to write the element symbols one after another, so sodium chloride is NaCl. When you read this, the capital letters tell you that a new element is beginning; it's a bit like a full stop and a capital letter between sentences.
  • Question 5

What are the names of the elements with these symbols?

CORRECT ANSWER
EDDIE SAYS
Once you can get question 3 and 5 right every time without looking, you know half the chemical symbols you need to know. Keep practicing them, and soon you will know them by heart. This set is a bit trickier than the first set; remember that sodium and potassium don't have obvious symbols. Na comes from the latin word "natrium", and K comes from the latin word "kalium", but you don't need to remember that!
  • Question 6

Use these words to fill in the blanks:

 

Aluminium

Atom

Bonded

Element

Mixture

Pure

CORRECT ANSWER
EDDIE SAYS
Remember that both elements and compounds are pure; once different atoms are bonded together as a compound, they count as a pure substance.
  • Question 7

Does this picture show an element, a compound or a mixture?

 

CORRECT ANSWER
Compound
EDDIE SAYS
This picture is a compound, because there are two different types of atom. It's actually ice; the red balls are oxygen and the white ones are hydrogen.
  • Question 8

Does this picture show an element, compound or mixture?

 

CORRECT ANSWER
Element
EDDIE SAYS
This picture is a pure element, because all the atoms are the same. They are all carbon atoms, and this picture shows the structure of diamond.
  • Question 9

How do you separate sand from water?

CORRECT ANSWER
Filtration
EDDIE SAYS
Filtration works because sand is solid, so it will get trapped in the filter. A sieve would work if the holes were smaller than the sand grains.
  • Question 10

Which of these are separation methods? Put a cross the box for every separation method.

CORRECT ANSWER
Filtration
Chromatography
Simple distillation
EDDIE SAYS
Well done for getting this far! This type of question isn't easy, because you don't know how many boxes to select. Don't panic- just carefully think about each option one at a time. Also, don't worry if you don't know how these separation methods work yet; there are some other activities to help you learn about them.
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