C12.1 - Pure substances and mixtures Flashcards
In advertising a product, what is pure taken to mean?
In advertising a product, pure is taken to mean ‘has had nothing added to it’
In advertising a product, pure is taken to mean ‘has had nothing added to it’ and that it is in its natural state.
Example
For example, pure orange juice means from freshly squeezed oranges
What does a pure substance mean to a chemist?
To a chemist, a pure substance is one that is made up of just one substance:
1. An element
Or,
2. A compound
You can use what to identify pure substances?
You can use:
1. Boiling points
2. Melting points
to identify pure substances
A test for water
A test for water is using white anhydrous copper sulfate
A test for water is using white anhydrous copper sulfate.
If water is present, it will turn blue.
But, what does this test tell you?
This test tells you if water is present
The test for pure water
The test for pure water is that its:
- Melting point is exactly 0 degrees Celsius
- Boiling point is exactly 100 degrees Celsius
Fixed points
Fixed points are the:
1. Melting
2. Boiling points
of an element or a compound
Why can you use melting points or boiling points to identify substances?
You can use melting points or boiling points to identify substances, because pure substances have characteristic, specific temperatures at which they:
- Melt
- Boil
You can use melting points or boiling points to identify substances, because pure substances have characteristic, specific temperatures at which they melt and boil.
Where can these fixed points be looked up?
These fixed points can be looked up in:
1. Databooks
Or,
2. Databases stored on computers
What will vary, depending on the composition of the mixture?
The:
1. Melting point
2. Boiling point
of a mixture will vary, depending on the composition of the mixture
A mixture does not have a sharp what?
A mixture does not have a sharp:
1. Melting point
Or,
2. Boiling point
Why does a mixture not have a sharp melting point or boiling point?
A mixture does not have a sharp: 1. Melting point Or, 2. Boiling point ,because it changes state over a range of temperatures
A mixture does not have a sharp melting point or boiling point, because it changes state over a range of temperatures.
What can this difference between pure substances and mixtures be used to do?
This difference between pure substances and mixtures can be used to distinguish if an unknown sample is a:
1. Pure substance
Or,
2. Mixture of substances
A mixture does not have a sharp melting point or boiling point, because it changes state over a range of temperatures.
This difference between pure substances and mixtures can be used to distinguish if an unknown sample is a pure substance or a mixture of substances.
So what is a quick and easy test of a compound’s purity?
So a quick and easy test of a compound’s purity is doing an experiment to find a melting point
The simple apparatus that can be used to determine the melting point of a solid in powdered or crystal form
The simple apparatus that can be used to determine the melting point of a solid in powdered or crystal form is:
- The substance being tested
- Oil or water bath
- Rubber band
- Capillary tube
- Opening to allow air in and out of the apparatus
- Thermometer
- (Heat)
What do impurities tend to do?
Impurities tend to:
- Lower the melting point of a substance
- Raise its boiling point
Impurities tend to lower the melting point of a substance and raise its boiling point.
What does the size of the difference from the fixed point of a pure substance depend on?
The size of the difference from the fixed point of a pure substance depends on the amount of any impurities mixed with it
Impurities tend to lower the melting point of a substance and raise its boiling point.
The size of the difference from the fixed point of a pure substance depends on the amount of any impurities mixed with it.
What happens the purer the compound is?
The purer the compound is, the narrower the melting point range
Impurities tend to lower the melting point of a substance and raise its boiling point.
The size of the difference from the fixed point of a pure substance depends on the amount of any impurities mixed with it.
The purer the compound is, the narrower the melting point range.
Example
For example, the melting point range of a purified sample of caffeine is 234-237 degrees Celsius
Formulation
A formulation is a mixture that has been designed to produce a useful product
A formulation is a mixture that has been designed to produce a useful product.
What are many consumer products made up of?
Many consumer products are made up of complex mixtures
A formulation is a mixture that has been designed to produce a useful product.
Many consumer products are made up of complex mixtures.
Example
For example, medicinal drugs are formulations
A formulation is a mixture that has been designed to produce a useful product.
Many consumer products are made up of complex mixtures.
For example, medicinal drugs are formulations
Formulations will often only contain between 5% and 10% of the active drug, which is the specific compound that affects the body to relieve symptoms, or cure an illness.
If taken in tablet form, what can they also contain?
If taken in tablet form, formulations can also contain:
- Colorants
- Sweeteners
- Smooth coatings to aid swallowing
- Fillers
- Other compounds to aid their dissolving at the most effective place in the digestive tract
What do scientists have to test?
Scientists have to test the effects that the other compounds in a formulation will have on the active drug in medicines
What are paints, like medicinal drugs?
Paints, like medicinal drugs, are also common formulations
Paints are also common formulations, like medicinal drugs.
In general, what will paints contain?
In general, paints will contain a:
- Pigment
- Binder
- Solvent
Paints are also common formulations, like medicinal drugs.
In general, paints will contain a pigment, a binder and a solvent.
Why do paints contain a pigment?
Paints contain a pigment to provide colour
Paints are also common formulations, like medicinal drugs.
In general, paints will contain a pigment, a binder and a solvent.
Why do paints contain a binder?
Paints contain a binder to help the paint:
- Attach itself to an object
- To form a protective film when dry
Paints are also common formulations, like medicinal drugs.
In general, paints will contain a pigment, a binder and a solvent.
Why do paints contain a solvent?
Paints contain a solvent to help the:
1. Pigment
2. Binder
spread well during painting by thinning them out
Paints are also common formulations, like medicinal drugs.
Where are other formulations found?
Other formulations are found in the range of cleaning agents used in the home
Paints are also common formulations, like medicinal drugs.
Other formulations are found in the range of cleaning agents used in the home.
Example
For example, washing-up liquids
Paints are also common formulations, like medicinal drugs.
Other formulations are found in the range of cleaning agents used in the home.
For example, washing-up liquids.
What do washing-up liquids generally contain?
Washing-up liquids generally contain:
- A surfactant
- Water
- Colouring and fragrance additives
- Rinse agent
Paints are also common formulations, like medicinal drugs.
Other formulations are found in the range of cleaning agents used in the home.
For example, washing-up liquids.
Washing-up liquids generally contain a surfactant, water, colouring and fragrance additives and a rinse agent.
Why do washing-up liquids generally contain a surfactant?
Washing-up liquids generally contain a surfactant, because it is the actual detergent that removes the grease
Paints are also common formulations, like medicinal drugs.
Other formulations are found in the range of cleaning agents used in the home.
For example, washing-up liquids.
Washing-up liquids generally contain a surfactant, water, colouring and fragrance additives and a rinse agent.
Why do washing-up liquids generally contain water?
Washing-up liquids generally contain water to thin out the mixture
Paints are also common formulations, like medicinal drugs.
Other formulations are found in the range of cleaning agents used in the home.
For example, washing-up liquids.
Washing-up liquids generally contain a surfactant, water, colouring and fragrance additives and a rinse agent.
Why do washing-up liquids generally contain colouring and fragrance additives?
Washing-up liquids generally contain:
1. Colouring
2. Fragrance additives
to improve the appeal of the product to potential customers
Paints are also common formulations, like medicinal drugs.
Other formulations are found in the range of cleaning agents used in the home.
For example, washing-up liquids.
Washing-up liquids generally contain a surfactant, water, colouring and fragrance additives and a rinse agent.
Why do washing-up liquids generally contain a rinse agent?
Washing-up liquids generally contain a rinse agent to help water drain off crockery
Examples of formulations
Examples of formulations are:
- Medicinal drugs
- Paints
- Washing-up liquids
- Fuels
- Alloys
- Fertilisers
- Pesticides
- Cosmetics
- Food products
In advertising a product, pure is taken to mean ‘has had nothing added to it’ and that it is in its what?
In advertising a product, pure is taken to mean ‘has had nothing added to it’ and that it is in its natural state
A test for water is using white anhydrous copper sulfate
If water is present, it will turn what?
A test for water is using white anhydrous copper sulfate.
If water is present, it will turn blue
A test for water is using white anhydrous copper sulfate.
If water is present, it will turn blue.
This test tells you if water is present.
It does not tell you if what?
It does not tell you if the water is:
1. Pure
Or,
2. Not
Impurities tend to lower the melting point of a substance and raise its boiling point.
The size of the difference from the fixed point of a pure substance depends on the amount of any impurities mixed with it.
The purer the compound is, the narrower the melting point range.
For example, the melting point range of a purified sample of caffeine is 234-237 degrees Celsius.
However, crude caffeine extracted from tea melts in what?
Crude caffeine extracted from tea melts in the range 180-220 degrees Celsius
Impurities tend to lower the melting point of a substance and raise its boiling point.
The size of the difference from the fixed point of a pure substance depends on the amount of any impurities mixed with it.
The purer the compound is, the narrower the melting point range.
For example, the melting point range of a purified sample of caffeine is 234-237 degrees Celsius.
However, crude caffeine extracted from tea melts in the range 180-220 degrees Celsius, showing what?
Crude caffeine extracted from tea melts in the range 180-220 degrees Celsius, showing it is an impure sample
A formulation is a mixture that has been designed to produce a useful product.
Many consumer products are made up of complex mixtures.
For example, medicinal drugs are formulations.
They will often only contain what?
Formulations will often only contain between 5% and 10% of the active drug
A formulation is a mixture that has been designed to produce a useful product.
Many consumer products are made up of complex mixtures.
For example, medicinal drugs are formulations.
Formulations will often only contain between 5% and 10% of the active drug, which is the specific compound that does what?
Formulations will often only contain between 5% and 10% of the active drug, which is the specific compound that affects the body to:
1. Relieve symptoms
Or,
2. Cure an illness
Paints are also common formulations, like medicinal drugs.
Other formulations are found in the range of cleaning agents used in the home.
For example, washing-up liquids.
Washing-up liquids generally contain a surfactant, water, colouring and fragrance additives and a rinse agent.
Washing-up liquids generally contain water to thin out the mixture, so it can do what?
Washing-up liquids generally contain water to thin out the mixture, so it can squirt more easily from the bottle
