Animations and Videos: More about Changing Substances

These downloadable videos and animations are part of the multimedia package Stuff and Substance, and are intended to be used to establish the concept of a substance. The individual video and animation files are provided separately here to allow flexibility in their use. The Stuff and Substance multimedia package provides a series of interactive pages that can be used by teachers or students in the classroom, including supporting commentary and questions, animations, videos, images, and teachers’ notes.

This section builds on ideas introduced earlier on in Stuff and Substance. Further developments of understanding are:

* The formula of a substance tells us which atoms a substance is made from and their relative numbers.

* A flame is a chemical reaction between two substances in a gaseous mixture which releases a great deal of energy. Normally, one of the substances is oxygen. The other substance may start in the gas state or go through changes to give a gaseous mixture. The presence of hydrogen atoms and carbon atoms in the other substance (fuel) results in water and carbon dioxide as products.

* Combustion is a reaction with oxygen that does not always produce a flame, for example carbon. Decomposition often precedes combustion when materials are heated. For example, when sugar and wood are set on fire the flames are the combustion of decomposition products, not sugar and wood in their gas states.

* Acids are a type of substance that has characteristic reactions with metals, metal oxides and metal carbonates.