Year 10 Homework: a bit more on decomposition reactions and word equations

by | Jun 17, 2012 | school posts, Year 10, K-11

Here are some notes you need for this part of the topic. Copy them into your book ready for tomorrow. Look at the short video as well

Word equations.

Copper carbonate decomposes when heated to form copper oxide and carbon dioxide. Instead of writing this information as a sentence chemists use something called a word equation to tell the same story. On the left hand side of the word equation we write down the substances that are reacting. On the right hand side we write down substances that are produced, the products.

Copper carbonate   heat —> copper oxide + carbon dioxide

Copy down and complete these equations:

                                    Zinc carbonate  heat—>

                                    Magnesium carbonate heat —>

                                    Calcium carbonate heat —>

Decomposition reactions often need heat to make them happen. Other decomposition reactions occur when a catalyst is present. Hydrogen peroxide is a water molecule with an extra oxygen atom. Manganese dioxide is a catalyst that helps it to decompose into water and oxygen molecules.

Hydrogen peroxide —-catalyst—-> water + oxygen

Have a look at the short video of water and hydrogen peroxide molecules. If the chemical formula for water is H2O what is the chemical formula for hydrogen  peroxide?

Now look at some oxygen gas being made.

Decomposition reactions year 10

by | Jun 12, 2012 | school posts, Year 10, K-11

Homework:

Here are some notes you need for this part of the topic. Copy them into your book ready for tomorrow. Look at the short video as well

Write in the date followed by the heading Decomposition Reactions: now copy in the rest of your notes

•Decomposition reactions occur when a large molecule is broken down into two or more simpler substances.
•Some molecules are so unstable they literally fall apart (nitrogen triodide, NI3)

Other substances, many carbonates for instance require heat before they break down into simpler molecules. Hydrogen peroxide is another chemical which is not very stable and undergoes a decomposition reaction when it is treated with a catalyst.

Heating carbonates:

•Carbonates other than sodium and potassium decompose on heating.
•Copper carbonate is a green powder
•When it is heated strongly it turns to a black powder.
•This black powder is copper oxide.
•Copper carbonate has the chemical formula CuCO3 
•Copper oxide has the chemical formula CuO
•As well as the black powder a gas that turns limewater milky is also produced. This is carbon dioxide, CO2
.
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