Chemistry - Is Matter Around Us Pure

Introduction

• A pure substance is that that consists of single type of particle or particles.

• Mixtures of two or more pure components without any undesirable substance are known as Mixtures, for example, water, minerals, soil etc.

• A homogeneous mixture of two or more substances is known as solution. For example, lemonade, soda water etc.

• Solution could be in any form such as – it could be in liquid, solid, or gaseous.

• Alloys are another example of mixture that contain homogeneous mixtures of metals; they cannot be separated into their components by physical methods. E.g. For example, brass is a mixture of zinc (approximately 30%) and copper (about 70%).

Significant Features of Solution

• Solution is normally a homogeneous mixture.

• The particles of a solution are even smaller than 1 nm (10-9 meter) in diameter and hence, these are not visible from the naked eyes.

• The path of light is not visible in a solution.

• The dissolved particles cannot be separated from the mixture by the simple process of filtration.

• The dissolved particles do not settle down when it left undisturbed.

• At a given temperature, when no more solute can be dissolved in a solution, it is known as ‘saturated solution.’

• At a given temperature, the amount of the dissolved particles present in the saturated solution, is known as solubility.’

Suspension

• A suspension is a heterogeneous mixture in which the solute particles do not dissolve, but rather remain suspended throughout the bulk of the medium, is known as ‘suspension.’

Significant features of Suspension

• Particles of a suspension are clearly visible from the naked eye.

• The particles of a suspension scatter a beam of light that passes through it and likewise, its path is visible.

• The salute particles can be separated from the mixture by the simple process of filtration.

Colloid

• A heterogeneous mixture is known as ‘colloid.’ E.g. mist, fog, smoke, face cream, etc.

• The size of colloid particles is too small to see from the naked eye.

• Colloid particles are big enough to scatter a beam of light passing through it and make the path visible.

• Colloid particles cannot be separated from the mixture by the simple process of filtration.

• The special filtration technique i.e. centrifugation, can be used to separate the colloidal particles.

Chromatography

• The process of separation of components of a mixture is called as chromatography; normally it is used for the color separation.

• Chromatography technique is used for separation of those solutes that dissolve in the same solvent.

Distillation

• The process of purifying a liquid by heating and cooling means is known as distillation.

Crystallization

• The process that separates a pure solid in the form of its crystals from a solution is known as ‘crystallization.’

Elements

• In 1661, Robert Boyle was the first scientist who used the term element; Antoine Laurent Lavoisier, a French chemist, was the first who experimentally define the term element.

• Element is as a basic form of matter that cannot be broken down into simpler substances by a chemical reaction.

• Elements normally can be categorized as metals, non-metals, and metalloids.

Metal

• A solid material, which typically is hard, ductile, malleable, shiny, and fusible with good electrical and thermal conductivity, is known as metal. E.g. gold, silver, copper, aluminum, etc.

• Mercury is the only metal that remains liquid at room temperature.

Non-metal

• All elements or substances, which are not metals, are known as non-metals. E.g. hydrogen, oxygen, iodine, carbon, etc.

• Non-metals have variety of colors and they are poor conductors of heat and electricity.

• Non-metals are not lustrous, sonorous, or malleable.

Compound

• A substance, composed of two or more elements, is known as ‘compound.’

• Compound is the result of the chemically combination of two or more elements in a fixed proportion.

• Properties of a compound are somehow different from its constituent elements, whereas, the properties of a mixture are the same as of its constituting elements or compounds.