Elements, Compounds and Mixtures
Matter may be classified into elements, compounds, and mixtures.
An element is a substance which cannot, by any chemical process, be split up into two, or more, simpler substances. Examples include – oxygen, hydrogen, chlorine, sodium, magnesium, etc.
A compound is a substance which contains two or more elements, chemically combined together. Examples include water (H2O), carbon (IV) oxide (CO2), sodium chloride (NaCl), etc.
A mixture contains two or more constituents which can easily be separated by physical methods. The components of mixtures may be elements or compounds or both.
Types of Mixtures:
1. Homogenous Mixture.
2. Heterogeneous Mixture.
Homogenous Mixture: Sometimes called solutions, these are mixtures of relatively uniform composition, where the components are in the same phase. Example sugar solution, air, seawater, brass, salt solution, etc.
Heterogeneous Mixtures are mixtures in which their components are in different phases e.g. kerosene and water, mud water, etc.
Other examples of mixtures are blood, crude oil, soil, urine, palm wine, milk, coca-cola.
Differences between Mixtures and Compounds:
|1.||May be homogenous or heterogeneous||Always homogenous|
|2.||Constituent elements are not chemically bonded together and therefore can be separated by physical means.||Constituent elements are chemically bonded and cannot be separated by physical method.|
|3.||Cannot be represented by chemical formula because the constituents are not in a fixed ratio.||Can be represented by chemical formula because the constituents are present in a fixed ratio.|
|4.||Properties of mixtures are a sum of their individual elements.||Properties of a compound differ from those of its component elements.|
1. (a) What is matter?
(b) Give three physical properties of matter.View Answer
2. Classify each of the following as physical change or chemical change
(i) Boiling of egg (ii) Melting of wax
(iii) Rusting of iron (iv) Digestion of GlucoseView Answer
3. Write four examples in each case of
(a) Physical change (b) Chemical changeView Answer
4. (a) define the following: (i) Compound (ii) Mixture
(b)Give three differences between Compound and MixtureView Answer
5. (a) State the difference between a homogeneous mixture and a heterogeneous mixture
(b) Classify the following into homogenous and heterogeneous mixtures; Brine, Sweat, Muddy water, Table salt, Sand, BloodView Answer