C8 Purity and Formulations (page 153) Flashcards
when you refer to a substance as being pure, what do this mean?
it means nothing has been added to it, so it’s in its natural state. For example: pure milk or beeswax.
What do a pure substance mean in chemistry?
it means something that only contains one compound or element throughout - not mixed with anything else.
What can you tell how pure a substance is?
The boiling or Melting point will tell you how pure a substance is.
Will a chemically pure substance melt or boil at a specific temperature?
yes it will.
How can you test the purity of a sample?
by measuring it’s melting or boiling point and comparing it with the melting or boiling point of the pure substance (which you can find from a data book)
The closer your measured value is to the actual melting or boiling point means what?
the closer to the melting or boiling point means the purer your sample is.
What will happen if impurities are in your sample regarding the melting point?
the sample will lower the melting point and increase the melting range of your substance.
What will happen if impurities are in your sample regarding the boiling point?
impurities in your sample will also increase the boiling point and may result in your sample boiling at a range of temperatures.
What are Formulations?
They are mixtures with exact amounts of components.
Why are Formulations useful?
they are useful mixtures with a precise purpose that are made by following a ‘formula’ (a recipe).
Each component in a formulation is present in a measured quantity, and contributes to the properties of the formulation so that it meets its required function.
Look at page 100 for more on mixtures.
What are paints formulations composed of:
Pigment - gives the paint colour, for example titanium oxide is used as a pigment in white paints.
Solvent - used to dissolve the other components and alter the viscosity.
Binder (resin) - forms a film that holds the pigment in place after it’s been painted on.
Addities - added to further change the physical and chemical properties of the paint.
Depending on the purpose of the paint, the chemicales used and their amounts will be changed so the paint produced is right for the job.
Why are Formulations really important in the pharmaceutical industry?
For example: by altering the formulation of a pill, chemists can make sure it delivers the drug to the correct part of the body at the right concentration, that it’s consumable and has a long enough shelf life.
Formulations can be found in everyday life products, give some examples?
cleaning products, fuels, cosmetics, fertilisers, metal alloys and even food and drink.
When you buy a product, you might find that it has information about its composition on the packaging. Give some examples of information?
For example, the ratio or percentage of each component. This tells you the product’s a formulation. It also lets you choose a formulation with the righ composition for your particular use.
The melting point of a sample of aspirin made by a student is measured as being between 128-132°C. The melting point and boiling point of pure aspirin are 136°C and 140°C respectively.
a) Give two reasons why the melting point measured shows that the sample is not pure? (2 marks)
b) Suggest a value for the boiling point of the sample? (1 mark)
a) The sample melts over a range of temperatures (1 mark). The melting point is lower than that of pure asprin (1 mark)
b) Any range or single value within the range: 141-200°C (1 mark)
(knowing how pure a product is can be bital in industries such as pharmaceuticals and the food industry. Luckily for us, chemsts have lots of different ways to make sure they’re making exactly what they want).
