Write a summary of lessons 2 In matter around us pure
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Answer:
We do know that matter is made up of particles which are arranged in a certain way. Gases particles are well separated and can freely move about, solids, on the other hand, have particles that are tightly packed, usually with no scope to move around.
Purity
Pure substances
Pure substances are elements or compounds.
They are made up of only one kind of entity.
They cannot be broken down into simpler entities by chemical or physical methods.
They have a fixed composition.
Example: Diamond, carbon dioxide.
Mixtures
Mixtures are formed by just mixing two or more pure substances (components) such that each substance retains its own chemical identity.
Types of mixtures
Types:
1. Homogeneous mixture
A mixture which has a uniform composition throughout is called a homogeneous mixture or solution.
Examples: sugar in water, salt in water.
Heterogeneous mixture
A mixture which contains physically distinct parts and has a non-uniform composition is called a heterogeneous mixture.
Examples: Mixture of salt and iron filings, sand and sugar.
Physical and chemical changes
se in temperature, they became less soluble in each other and in water, but more soluble in organic solvents.
Pressure – For the majority of solid and liquid solutes, pressure does not affect solubility. The solubility of gas is directly proportional to the pressure of this gas.
Types of solutions based on the concentration of the solution
Three types of solutions exist based on the concentration of the solution:
Dilute
Concentrated
saturated solution.
Ways of representing the concentration of a solution
The concentration of a solution can be represented in many ways
(i) Mass by the mass percentage of a solution = (Mass of solute / Mass of solution) × 100
(ii) Mass by volume percentage of a solution = (Mass of solute/ volume of solution)×100
Suspensions
Suspension and its properties
A suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the bulk of the medium.
The solute particles settle down when a suspension is left undisturbed.
They can be separated from the mixture by filtration.
Colloids
Types of mixtures based on particle size
Classified into:
The solute-like component of the dispersed particles in a colloid form the dispersed phase.
Dispersion medium
The component in which the dispersed phase is suspended is known as the dispersing medium.
Aerosol
A colloidal solution with dispersed phase solid/liquid and dispersing medium gas is called Aerosol. e.g. clouds
Foam
A colloidal solution with dispersed phase gas and dispersing medium solid/liquid is called Foam. e.g.Shaving cream.
Sols
A colloidal solution with dispersed phase solid and dispersing medium liquid is called Sol. e.g. Milk of magnesia, mud.
Gels and emulsions
A colloidal solution with dispersed phase liquid and dispersing medium solid is called Gel.
A colloidal solution with dispersed phase liquid and dispersing medium liquid is called Emulsion.
Evaporation
The process of conversion of water into water vapour is known as evaporation.
It can be used to separate the volatile component (solvent) from its non-volatile solute.
Introduction to Separation
Separation of components of a mixture
Heterogeneous mixtures can be separated into their constituents by simple physical methods.
Methods include: handpicking, sieving, filtration.
Separation of a mixture of two immiscible liquids
Separation of a mixture of two immiscible liquids is done by using a separating funnel.
Applications: To separate a mixture of oil and water, in the extraction of iron from its ore.
Centrifugation
Centrifugation uses centrifugal force for the separation of two liquids in a mixture.
Here, a denser component of the mixture migrates away from the axis, and lighter component migrates towards the axis.
Sublimation
Sublimation is the transition of a substance from solid phase to gaseous phase without changing into liquid phase.
Example: Naphthalene balls undergo sublimation.
Chromatography
Chromatography is used to separate the different components in a liquid mixture.
Compounds
Compounds are the substances consisting of two or more different types of elements in a fixed ratio of its atoms.
Difference between mixtures and compounds
Mixtures are constituted by more than one kind of pure form of matter, known as a substance.
Types: Homogeneous Mixtures, Heterogeneous Mixtures
When two or more elements chemically combine in a fixed ratio by mass, the obtained product is known as a compound.
Explanation:
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