Knowt
Chapter 2-Is Matter Around Us Pure?(Mixtures and Solutions)
When we look around, we can observe that the majority of the matter is composed of two or more pure components.
Examples-sea water, minerals, dirt, and others.
What is a Mixture?
More than one type of pure form of matter makes up mixtures.
We are aware that the physical process of evaporation can physically remove dissolved sodium chloride from water.
However, sodium chloride cannot be physically divided into its chemical components because it is a pure material in and of itself.
Similar to this, sugar is a substance that is uniformly composed and only comprises one type of pure matter. Soil and soft drinks are not single pure.
TYPES OF MIXTURES
HOMOGENEOUS MIXTURE
A homogeneous mixture is a gaseous, liquid or solid mixture that has the same proportions of its components throughout a given sample.
It is uniform in composition throughout.
There is only one phase of matter observed in a homogeneous mixture.
Example-A mixture of salt and water, A mixture of water and sugar.
HETEROGENEOUS MIXTURE
A heterogeneous mixture is a mixture where throughout the solution the composition is not uniform.
There are two or more phases of a heterogeneous mixture.
Example-Sand, oil and water
What is a Solution?
A homogenous mixture of two or more components is referred to as a solution.
e.g. Lemonade, soda water etc. are all examples of solutions.
A solution is typically thought of as a liquid that has a solid, liquid, or gas dissolved in it. But there are also solid (alloy) and gaseous solutions that we can use (air). Homogeneity exists at the particle level in a solution. Lemonade, for instance, has a consistent flavour throughout. This demonstrates that the sugar or salt ions are spread equally throughout the liquid.
COMPONENTS OF A SOLUTION
Solute- A substance that is dissolved in a solution is called a solute.
Solvent- A liquid material with the ability to dissolve or disperse one or more other substances.
Eg-In a salt and water solution,salt is solute and water is solvent
ALLOY
Alloys are mixtures of two or more metals or a metal and a non-metal that are impossible to physically separate into their component parts.
However, because an alloy demonstrates the characteristics of its parts and can have a changeable composition, it is still regarded as a mixture.
For instance, brass has roughly 30% zinc and 70% copper.
Specifications of a solution
• A homogenous mixture is a solution which has extremely small particle size less than 1 nm (10-9 metres). Therefore, they are invisible to the human sight. Therefore, in a solution, the path of light is not visible. • The filtration procedure is unable to remove the solute particles from the mixture. When left undisturbed, the solute particles do not settle down; therefore, a solution is stable.
CONCENTRATION OF A SOLUTION
The ratio of the solute to the solvent can be changed in a solution. A solution can be classified as concentrated, dilute, or saturated depending on the amount of solute it contains. Dilute and concentrated are comparative terms.
WAYS TO EXPRESS CONCENTRATION
Mass by mass percentage of a solution
(Mass of solute/Mass of solution)x100
Mass by volume percentage of a solution
(Mass of solute/Volume of solution)x100
Volume by volume percentage of a solution
(Volume of solute/Volume of solution)x100
What is a suspension?
The term "suspension" refers to a heterogeneous combination in which the solute particles do not dissolve but rather remain suspended throughout the majority of the medium. A suspension contains particles that are visible to the naked eye.
Properties of a Suspension
Suspension is a heterogeneous mixture.
The particles of a suspension can be seen by the naked eye.
The particles of a suspension scatter a beam of light passing through it and make its path visible.
When a suspension is undisturbed, the solute particles settle down, indicating that the suspension is unstable. Filtration can be used to separate them from the mixture. When the particles settle, the suspension breaks and it does not scatter light any more.
COLLOIDAL SOLUTION
Colloids are mixtures in which minute insoluble particles of one substance are suspended in another substance. They are also known as colloidal solutions or colloidal systems. A colloid's suspended particles might be anywhere from 1 and 1000 nanometers in size (10-9 metres).
Because of the small size of colloidal particles, we cannot see them with naked eyes.
A visible light beam can easily be scattered by these particles.
Tyndall effect can be observed in colloidial solution.
Properties of a colloid
A colloid is a heterogeneous mixture
The size of particles of a colloid is too small to be individually seen by naked eyes
Colloids are big enough to scatter a beam of light passing through it and make its path visible.
They do not settle down when left undisturbed, that is, a colloid is quite stable
The components of a colloidal solution are the dispersed phase and the dispersion medium
DISPERSED PHASE
The solute-like component or the dispersed particles in a colloid form the dispersed phase
DISPERSION MEDIUM
The liquid, gaseous, or solid phase in a two-phase system in which the particles of the dispersed phase are disseminated is referred to as the dispersion medium.
Colloids are classified according to the state (solid, liquid or gas) of the dispersing medium and the dispersed phase
Separating the Components of a Mixture
Heterogeneous mixes can be separated into their individual components using a simple
Physical techniques that we employ on a daily basis, such as handpicking, sifting, and filtration.
CENTRIFUGATION
When solids are present in a liquid, they can sometimes be very tiny and pass through filter paper. The filtration method is not appropriate for such particles. Centrifugation is used to separate these combinations.
The idea is that when particles are rapidly spun, the lighter particles remain at the top while the denser particles are driven to the bottom.
Applications-
Used in diagnostic laboratories for blood and urine tests.
Used in dairies and home to separate butter from cream.
Used in washing machines to squeeze out water from wet clothes.
SUBLIMATION
The sublimation technique is used to separate mixtures containing a sublimable volatile component from a non-sublimable impurity. Solids like naphthalene, anthracene, and ammonium chloride are some examples of those that sublime.
DISTILLATION
Distillation is used for the separation of components of a mixture containing two miscible liquids that boil without decomposition and have sufficient difference in their boiling points.
To separate a mixture of two or more miscible liquids for which the difference in boiling points is less than 25 K, fractional distillation process is used.
For example, for the separation of different gases from air, different factions from petroleum products etc.
CRYSTALLIZATION
Purification of solids is done through crystallisation. For instance, the salt we obtain from seawater may contain a variety of contaminants which can be removed through the crystallisation process.
Crystallisation is a process that separates a pure solid in the form of its crystals from a solution.
Crystallisation technique is better than simple evaporation technique as –
some solids decompose or some, like sugar, may get charred on heating to dryness.
some impurities may remain dissolved in the solution even after filtration. On evaporation these contaminate the solid.
What are the Types of Pure Substances?
ELEMENTS
Element is a basic form of matter that cannot be broken down into simpler substances by chemical reactions
Elements can be normally divided into metals, non-metals and metalloids.
PROPERTIES OF METALS
They are either golden-yellow or silvery-grey in colour.
When struck, they produce a sonorous sound. Gold, silver, copper, iron, sodium, and potassium are some examples of metals.
They are heat and electricity conductors. • They may be drawn into wires because they are ductile. • They may be hammered into thin sheets and are malleable.
They are lustrous (shiny).
PROPERTIES OF NON METALS
They exhibit a range of colours.
They are poor heat- and electricity-conductors.
They are not lustrous, sonorous, or bendable. Hydrogen, oxygen, and iodine are a few non-metals as examples.