Science Infoblog

Year 10 students studying  NCEA level science this year have made a number of 5 minute tutorials that cover aspects of their course. Have a look at them. The first video deals with acids and bases.

The second video covers motion and distance time graphs. Do you find these tutorials useful. Why don’t you pick a topic with some friends and make your own video.

Test your knowledge about metal chemistry here.

Metals combine with oxygen to form metal oxides. For example iron wool burning in oxygen produces iron oxide

The chemical equation.

Iron                +     Oxygen     –>    Iron oxide

Aluminium     +     Oxygen     –>     Aluminium oxide

Aluminium is reactive enough to chemically combine with oxygen atoms that are already attached to another metal atom.

Aluminium     +     Iron  oxide     –>     Aluminium oxide     +     iron

This is known as a thermite reaction . A huge amount of heat is given out and the iron formed is molten. The reaction has been used by NZ rail to weld continuous sections of line together.

Some metals are clearly very reactive. Sodium and lithium react violently with water and calcium dissolves quickly.
Other metals dissolve in acids and the rate at which they dissolve tells you something about how reactive they are. If they give off lots of bubbles rapidly they are reactive. Aluminium is out of order because it has a protective layer of oxide. It appeqars to be unreactive and this fact often crops up in NCEA level 1 exams.
A list of metals from the most reactive to the least reactive is known as the reactivity series.

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.