Hello
readers! Today’s topic will be on “Elements, Compounds and Mixtures” as
requested by another Science teacher, Mrs Fromey. Bonjour Madame Fromey! Thanks
for visiting my blog ;) I
hope you’ll be reading this post and hopefully it’ll help your lessons :)
Elements
An element is a pure substance which contain only one kind of atom. Element cannot be broken down into two or more simpler substances by either physical or chemical means. It can exists as either atoms (e.g. Argon, Copper, Gold) or molecules (e.g. Hydrogen, Bromine, Oxygen)
You might now wonder...what are atoms and molecules? Atom is the smallest particle of an element whereby molecule is made up of two or more atoms that are chemically combined together.
Still confuse? Let me give you several diagrams that might help you understand more about elements that can exist as either atoms or molecules.
Examples of atoms:
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| Noble gas atoms such as Helium, Neon and Argon |
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| Gold atoms |
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Examples of molecules:
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| Molecules of bromine gas (on top) and liquid bromine (below) |
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| Molecules of elements |
Below is tabular display of chemical elements called the Periodic Table of the Elements which are organized based on its properties. (please click picture below to enlarge)
Compounds
A
compound is a
pure substance which
is made of two or more elements chemically combined together. It
can be broken down into two or
more simpler elements
by chemical means only (but not by physical means). It has
different properties from its component elements and it always contain the same ratio of its component atoms (
fixed composition).
Examples of compounds:
As you can see from the above examples, the compound is made up of different elements (two or more) chemically combined together.
Making a compound from its elements
Example: Making water from hydrogen and oxygen (2H2 + O2 --> 2H2O)
Notice that both elements are in gaseous state initially but once they form compound water, it is liquid. This shows that a compound has different properties from its component elements.
Another example is brown copper burns with green chlorine gas and form yellowish-green copper chloride.
Breaking a compound into its elements
Example: Breaking down molten sodium chloride into sodium and chlorine by electrolysis
(2NaCl --> 2Na + Cl2)
**Electrolysis is the process of breaking down compounds by using an electric current
Mixtures
A mixture is made of two or more substances mixed but not chemically joined together. It can be separated into its components by physical means. It has the same properties as all its component substances and do not have a fixed composition of the substances.
An example of mixture is air which consists of different gases such as nitrogen, oxygen, carbon dioxide and water vapour. All of these gases are colourless and odourless and so does air. Air still retains many of the properties of its components.
Other examples of mixtures are muddy water which can be separated into soil and water by filtration or a mixture of copper powder with iron filings which can be separated by using a magnet.
Below are diagrams of several other examples of mixtures to help you understand better:
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| A mixture of two elements (e.g. argon gas and hydrogen gas) |
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| A mixture of an element and a compound (e.g. hydrogen and ammonia gas) |
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| A mixture of two compounds (e.g. carbon dioxide and water vapour) |
Click the link below to test your knowledge on Elements, Compounds and Mixtures. Good luck and have fun playing the quiz :)
http://www.funtrivia.com/playquiz/quiz148865110c980.html
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