Tap water is not the pure form of water, it contains a large number of salts, elements, bacteria and other impurities,

The mixture consists of constituents in indefinite proportion. It may change over time. Air has 78% Nitrogen, 21% Oxygen and 1% other constituents such as $CO _2$, water vapour etc. About 100 years ago the proportion of $CO _2$ in the air was about 0.029% and now it is 0.035%. Thus we see that it's proportion has changed.

A mixture consists of constituents in indefinite proportion. It may change over time. Air has 78% Nitrogen, 21% Oxygen and 1% other constituents such as CO2, water vapour etc. About 100 years ago proportion of CO2 in air was about 0.029% and now it is 0.035%. Thus we see that it's proportion has changed. Therefore, air is a mixture.

Elements are the fundamental particles of all kinds of matter. They can't be separated by any physical or chemical means.

The important point regarding mixture is that it always retain the original property of its components, so mixture dont have any definite set of properties.

Solution of salt in water, air, alloy are all examples of homogeneous mixture. They are formed by mixing different elements in to form a mixture which is in single state. Hence they are also called as homogeneous mixture.

A substance which contains two or more different particles is known as mixtures. Example: the Salt solution is made up of two components, salt and water. Therefore, the salt solution is a mixture.

Blood is an example of heterogeneous mixture.

Air is a homogeneous mixture. However, the Earth's atmosphere as a whole is a heterogeneous mixture. Alloys are made when two or more metals are mixed together. They usually are homogeneous mixtures. Examples include brass, bronze, steel, and sterling silver.

When two liquids do not mix, they form two separate layers and are known as immiscible liquids. These two liquids can be separated by using a separating funnel. It will separate the immiscible liquids into two distinct layers depending on their densities. The heavier liquid forms the lower layer while the lighter one forms the upper layer. Kerosene has lower density than water and hence forms the upper layer.

A mixture is a material system made up of two or more different substances which are mixed but are not combined chemically. A mixture refers to the physical combination of two or more substances on which the identities are retained and are mixed in the form of solutions, suspensions, and colloids.

Water and methane are both made up of two different elements. Water is made up of oxygen and hydrogen whereas methane consists of carbon and hydrogen. Compounds are substances that contain atoms of at least two elements chemically combined. Hence, water and methane are compounds.

Smog is a mixture of smoke and fog. There is no chemical combination and properties of smog are dependent on the properties of its constituent element.

A mixture is composed of two or more pure substances and a mixture always shows the properties of their constituents.

All are the examples of separation of substances. 

Distilled water is the pure form of water with no impurities present in it;

Mixtures can be obtained by a combination of elements and compounds. Thus when they are separated, it can give both elements and compounds, depending upon the constituents of a mixture.
Example: Air is the mixture of various gases. It on separation gives oxygen, nitrogen, carbon dioxide, etc. 

$BaCl _2+H _2S\longrightarrow BaS+2HCl$
                                  $1.69$ $g$
For $1$ $mole$ of $H _2S$ produce $1$ $mole$ of $BaS$
So, $1$ $mole$ $H _2S\longrightarrow 1$ $mole$ $BaS$
            $34$ $g$                      $169$ $g$
                      $(x)\longleftarrow 1.69$ $g$
$\implies x=\cfrac {1.69\times 34}{169}=0.34$ $g$
Amount of $H _2S$ needed $=0.34$ $g$

Mixture, a physical combination of two or more pure substances. A mixture is distinguished from a compound, which is formed by the chemical combination of two or more pure substances in a fixed, definite proportion. 

A true solution (or simply a solution) is a homogeneous mixture, i.e., in a true solution, the solute and solvent molecules cannot be distinguished even under a microscope because the size of the particle is very small.

A ) Brass is an alloy made of copper and zinc.
B) Dry ice, sometimes referred to as "cardice" (chiefly British chemists), is the solid form of carbon dioxide, so it is a compound.
C) Aerated drink would be anything that would have fizz (gas) filled in it. For example, your pepsi, coke, thums up, mirinda etc.
D) Diesel is mixture of many hydrocarbons.
Options C & D are correct.

Impure substances are commonly called mixtures. A mixture is a material containing two or more elements or compounds that are in close contact and are mixed in any proportion. The constituents of mixtures exhibit their individual properties. These constituents can be separated by physical means.

Generally, an alloy is a mixture of two or more elements, at least one of which is a metal, and which exhibits metallic bonding characteristics. It may be either homogeneous (eg a solid solution; i.e. single phase; e.g brass) or heterogeneous ( a mixture of metallic phases e. g. Steel— the iron/carbon system) 

Liquid in gas $ex>$ Fog,Mist,cloud.

Sublimation is the transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase.
Salt and ammonium chloride can be separated using this.
Crystallization is also a chemical solid-liquid separation technique, in which mass transfer of a solute from the liquid solution to a pure solid crystalline phase occurs.
Pure copper sulphate from an impure sample.
Distillation is a process of separating the component substances from a liquid mixture by selective evaporation and condensation. Distillation may result in essentially complete separation (nearly pure components), or it may be a partial separation that increases the concentration of selected components of the mixture.
A separating funnel is a glass funnel with a tap at the bottom. A separating funnel is a separation technique that is used for two liquids that do not dissolve in each other.

Heating is a physical means to separate a mixture of two substances which are not chemically together as in a compound so they are separated by heating.

An impure substance is a substance that contains two or more elements or compounds that are not bonded chemically . So Milk is an impure substance .

In a mixture constituents exhibit their own individual property.

A solution is a mixture of two or more substances in a single phase. At least two substances must be mixed in order to have a solution. Since solutions are mixtures, their compositions may vary over a very wide range. The concentrations may be expressed using a variety of measures.

A mixture is a combination of two or more materials, compounds or elements where there is no chemical combination or reaction.

The mixture is a combination of two or more elements in such a way that no chemical reaction occurs. So, a mixture is a physical combination of two or more elements.

Liquor ammonia is a concentrated solution of ammonia in water due to which, it forms a liquid-gas mixture with soda water(carbon dioxide gas under pressure)

Steel is alloy of iron and carbon, so it is forming a solid - solid homogeneous mixture.

In chemistry, a mixture is a material system made up of two or more different substances which are mixed but are not combined chemically. A mixture refers to the physical combination of two or more substances in which the identities are retained and are mixed in the form of solutions, suspensions, and colloids.

The individual substances in a mixture can be separated using different methods, depending on the type of mixture. These methods include filtration, evaporation, distillation and chromatography.

In chemistry, a mixture is a material system made up of two or more different substances which are mixed but are not combined chemically. A mixture refers to the physical combination of two or more substances in which the identities are retained and are mixed in the form of solutions, suspensions, and colloids.

Separation of a mixture is done in order to:-

Separation of a mixture is done in order to :

White vitriol and blue vitriol are known as isomorphous because they have similar chemical formula and closely similar in shape.

It is possible to separate seawater to obtain pure substances like salt and waters. For this various physical and chemical processes are used.

The crude oil can be separated into various substances like petrol, diesel, kerosene, wax, etc. These are very useful in supplying energy and in various processes.