Science Quiz - Compounds 01 (Answers)
This KS3 Science quiz takes a look at compounds. A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Some compounds are made up from two non-metal elements that have joined together, for example water and carbon dioxide. This type of compound is made from molecules. Other compounds are made when a metal chemically combines with a non-metal. This type of compound is made from a giant structure, not molecules. Sodium chloride and calcium oxide are two examples.
Naming compounds is something that takes a bit of practice to learn - some people get how to do it faster than others. Working out the name of a compound follows certain rules but we don't have the room to tell you all of them here.
You will probably find it easier to name a compound made from one metal and one non-metal easier than naming compounds made from non-metals. The name of the metal comes first and the name of the non-metal is changed to end in -ide. When you see the name of a compound that ends in -ate, you can tell that there is oxygen in it. An example is that sodium sulfate is the metal sodium joined to sulfur and oxygen.
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You can find more about this topic by visiting BBC Bitesize - Elements, compounds and mixtures
In theory, the elements could be separated using chemical reactions but that is not always straightforward
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The easy way to do this is to count the capital letters in the formula. Each element has exactly ONE capital letter. In CaCO3, the three elements are Ca, C and O
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There are two elements joining together so the name ends in -ide
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It contains one atom of carbon joined to four atoms of hydrogen. Can you see how you get that from the formula?
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Chlorine is an element and therefore appears on the periodic table. The others do not appear on the periodic table so they cannot possibly be elements
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One Cu, one S, four O. If you find reading formulae difficult, don't worry, you will have plenty more practice when you study science at GCSE. There are some simple rules that need to be learned, not everyone sees them straight away
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The clue is in the word tetra - that means four and since it is in front of the 'chloride' bit of the name, there must be four chlorine atoms involved
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Remember, compounds that are made from two non-metals joined together exist as molecules
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Whoever wrote it forgot to change the name of chlorine to chloride in the compound
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If you count up the number of atoms on each side of the equation, they are the same - two of magnesium and two of oxygen
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