Reactions of acids, balanced equations and a connection to the space shuttle

We have studied the reactions of acids with:

  • bases
  • metals
  • and today carbonates

We have used word equations to produce fully balanced chemical equations in three steps. For a little more information on this process have a look at this post about the space shuttle being blasted into orbit on the back of  a huge pop test.

the basic word equations we use are:

acid     +     base                      —–>     salt     +     water

acid     +     metal                    —–>     salt     +     hydrogen

Acid     +    carbonate               —–>    salt      +     carbon dioxide     +      water

Use these word equations to answer the questions below.

Magnesium atoms reacting

At the conclusion of your last lesson you knew more about the atom than Ernest Rutherford, apologies 1st Baron Rutherford of Nelson at the height of his career. The most fascinating thing about atoms is their size.

  • they are tiny compared to us
  • the nucleus of an atom is tiny compared to the rest of the atom

If you pumped up the nucleus of the smallest atom hydrogen to the size of a soccer ball and placed it on the centre circle of field at Rutherfield College gthe electron would be the size of a pea and you would find it somewhere around the sky tower in central Auckland!

Have a look at the video comparing the size of atoms to blueberries

The magnesium atoms in a piece of magnesium metal can be made to react chemically by either heating them in a bunsen flame or dropping them into an acid. (it didn’t matter whether it was dilute sulphuric acid or hydrochloric acid)

The reaction with acid produced a lighter than air gas that exploded with a pop when it was lit. Can you remember which gas it was?

Year 11 chemistry:balancing chemical equations, reactions of metals and acids

Year 11 chemistry:balancing chemical equations, reactions of metals and acids

Chemistry has its own language with words and sentences.

Chemistry has its own language with words and sentences.

To a chemist the words are chemical formulae. When chemical formulae are joined together in a sentence we call this a chemical equation.

Hydrogen and oxygen mixtures explode when lit. In a test tube this explosion is heard as a “pop”. We call the test for hydrogen “the pop test”

The space shuttle is launched into space with three main engines. Each engine produces 1.8 Meganewtons of thrust. The engines are powered by liquid hydrogen and oxygen fuel stored in the large central rust coloured tank.

The space shuttle is blasted into space on the back of a mega “pop test” The two tanks on either side of the shuttle are solid fuel boosters.

Hydrogen molecules and oxygen molecules react with each other to form water molecules. A chemist rewrites this sentence as a word equation

hydrogen + oxygen —–> water

Chemists use chemical formulae instead of words. Finally chemists need to count the numbers of atoms involved. We need to have the same numbers of atoms after the reaction that we had at the start.

When we do this we end up with a fully balanced chemical equation. As far as NCEA level 1 is concerned here are the steps.

  • word equation…..achievement
  • with chemical formulae……merit
  • a fully balanced chemical equation…..excellence

Check out the video to see how we get a fully balanced equation for the “pop test”

try balancing the equations that describe metals reacting with acids.

NCEA Level 1 Chemistry: writing chemical formulae:

In ionic compounds the total charge of the positive ions is balanced by the total charge of the negative ions.

  1. write down the formula of the metal ion
  2. write down the formula of the negative ion
  3. if the charge is unbalanced add another ion of the opposite charge.
  4. repeat until charges balance

Watch the video to see how this works.

When you master this skill you are well on your way to becoming a chemistry geek!. Good luck

……………. and final finally……… a mars bar to the first person who can identify the video music.

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