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When two or more elements or compounds are brought together, they mix together without losing their individual properties. These are called mixtures. A mixture may be defined as that containing two or more substances in varying compositions. Air is a mixture of several gases. It contains elements such as oxygen, nitrogen and compounds such as CO2 and water vapour.

A mixture of iron and sulphur is taken in a dish. A magnet is brought near this mixture. What happens to the mixture? Only the iron filings get attracted to the magnet. Add carbon disulphide to the mixture. What do you notice? The sulphur particle dissolves while the iron fillings remain unaffected. What do you understand from this activity? We can understand that individual components of a mixture retain their original properties. Here iron retains its property of getting attracted to a magnet and sulphur retains its property of dissolving in carbon disulphide.

Mixtures can be classified as heterogeneous or homogeneous. Solutions are homogenous mixtures at the particle level.

A heterogeneous mixture is usually apparent at the macroscopic level. It is obviously a mixture of two different substances (salt and pepper, oil and vinegar, etc.) that may or may not be in different physical states (liquid and gas state).

Homogenous mixtures appear to be one substance at the macroscopic level. This means that only one physical state is apparent (i.e. only solid, only liquid, etc.) and two or more substances are mixed in such a way that it is impossible with the naked eye to distinguish the individual substances. An example is margarine. Margarine is usually made up of at least three substances. However, all the substances mix to produce what looks like "one" substance.

Take a test tube and add salt to it. Stir it. What do you notice after the salt is being added? The resulting mixture has the same colour and taste throughout its bulk. The homogenous mixtures appear be one substance at the macroscopic level. So the resultant solution is a homogenous solution.

Many, but not all, homogenous mixtures are solutions. A solution is a homogenous mixture that is also homogenous at the particle level. A solution is formed when tiny individual particles (<1 mm in diameter) of one substance are uniformly dispersed among the individual particles of the other substance. An example of a solution is sugar water. Individual molecules of sugar are uniformly distributed among molecules of the water.

Some homogeneous mixtures are not solutions. e.g. margarine and milk. At the microscopic level, the particles that comprise margarine or milk are not randomly scattered but, instead, clump together. A homogeneous mixture like margarine or milk is called a colloid. In a colloid, the dispersed particles, or clumps of particles, are greater than 1 mm in diameter.

Differences between compounds and mixtures





They are made up of two or more elements which are chemically combined.

They are made up of two or more substances which are not chemically combined.


A compound has a definite composition.

The composition of a mixture may vary greatly by weight.


Properties of a compound are different from those of the constituent elements.

The properties of a mixture can be separated by physical methods.


The constituent elements of a compound cannot be separated by physical methods.

The constituent of a mixture can be separated by physical methods.


A compound is always homogeneous.

A mixture may or may not be homogeneous.


Energy change occurs during the formation of a compound.

No energy change occurs during the formation of a mixture.

To study the difference between a mixture and a compound
Take 56g iron filings in a china dish. Mix 32g sulphur powder into it. Mix them thoroughly. In another china dish take 56g iron filings and 32g sulphur powder. Heat this dish to a high temperature. What do you observe?

Now, take a magnet. Pass it through both the dishes. Record your observations.
When the iron filings and sulphur powder are taken in the china dish, they formed a mixture. Iron and sulphur do not combine with each other. Both sulphur and iron retain their own properties. When we bring a magnet near the mixture, the iron filings get attracted to the magnet.


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