Question

Classify the following as element, mixture or compound:

Sea water

Answer 1

Element:

• An element is a pure substance that cannot be split into simpler substances and comprises only one type of atom.
• Example: Hydrogen$\left({\mathrm{H}}_2\right)$, Copper$\left(\mathrm{Cu}\right)$, etc.

Compound:

• A compound is a pure substance in which elements combine chemically in a fixed composition to give a compound.
• They can be broken down into elements that make up the compound by using chemical or electrochemical methods.
• The properties of the compound are entirely different from the elements from which it is formed.
• Example: Water$\left({\mathrm{H}}_2\mathrm{O}\right)$, Common salt i.e., Sodium chloride $\left(\mathrm{NaCl}\right)$

Mixture:

• When two or more substances (elements or compounds or an element and compound) are mixed in any proportion.
• The components of a mixture can be separated by physical methods of separation.
• Example: A mixture of Sand and Iron $\left(\mathrm{Fe}\right)$ can be separated by the use of a magnet (physical process) where Iron gets attracted to the magnet leaving behind the sand.

Seawater is an example of a mixture.

• Sea water can be classified as a mixture. This is because sea water is composed of more than one substance i.e., various salts, gases, and water along with other organic and inorganic matter.
• The composition of various salts, gases, and water along with other organic and inorganic matter can vary. It is having variable compositions Ie, not in a fixed proportion.
• The components of seawater i.e., salt, mostly Sodium chloride $\left(\mathrm{NaCl}\right)$ can be separated by using physical methods of separation like evaporation.
• It is not an element because it contains more than one type of particle.
• It is not a compound because the components are not in a chemically combined state in a fixed composition by mass.

Hence sea water is a mixture.