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Science - Reversible and Irreversible Change

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by

Neil Paton

on 6 December 2012

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Transcript of Science - Reversible and Irreversible Change

Reversible and Irreversible Changes Science - Materials What types of changes
can we identify? Reversible Changes What do we know? Is a change that can be undone or reversed.
These changes are temporary and can return to the original state. Melting and Boiling Some changes from heating can result in a change from a solid to a liquid, or a liquid to a gas. Dissolving Is when a soluble material dissolves in water. Irreversible Changes Is a change that can NOT be undone or reversed.
It is also known as non-reversible, permanent or chemical changes. Heating Some permanent changes can occur from just heating an object. Chemical Reactions These are changes that alter the actual material in some way. The result is often a new material of some sort. Some times changing it back is a difficult process... but it can still be done. This type of change often creates a new material. Insoluble Mixture Insoluble means that it can not dissolve.
Consider muddy water... the water may look different but it has not changed. Freezing Changing the temperature of something can change the material. Suspension Suspension is when the material floats with in the liquid. It would appear to be a solution unless you looked really closely. Burning Burning is a permanent change to something.
You cant return ash and smoke into wood. Examples of chemical changes include baking a cake and or making bread.

The ingredients react with each other in the heat to create a new material. Cooking an egg is a permanent change. You can't un-cook something! This is specifically for flammable materials. But what about a candle is it burning or melting? Water can be frozen into ice, changing from liquid to solid but it can be changed back. So this change is reversible. This can not be changed back into its individual ingredients so it is a irreversible change. So this change is irreversible. So this change is irreversible. These changes like boiling water can be reversed by condensation. Consider where rain comes from? So this is a reversible change. By filtering and separating the materials we can see that there is actually no change to the material. It is just a mixture of two materials in one solution. This can be reversed. Consider a cup of coffee...
The water is the solvent,
The coffee granules are the solute.

And when they are mixed the coffee dissolves into the liquid creating a solution. This can be reversed by evaporation but is difficult to get back to the exact original form. But it is possible. So this change is reversible. A good example of this is paint.
In the liquid is loads of little bits of paint that leave a die on the water. This can happen if you put too much of a solute like sugar in a solvent like water. This can be changed back but it is a complex process.
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