Mixture	Compounds
1. elements or compounds just mix retaining the properties of a constituent substance	1. Element reacts to form a new substance that has totally different properties.
2. A mixture has a variable composition	2. The composition of the new substance or compound is fixed.
3. The constituent can be separated fairly easily by physical methods.	3. The constituents can be separated only by chemical methods.

Comparison of properties of a true solution, colloidal solution, and suspension

property	True solution	Colloidal solution	Suspension
(1) Appearance	homogeneous and transparent	Heterogeneous and translucent	heterogeneous and opaque
(2) particle size	< 1 nm (10-7 cm)	1 nm - 100 nm	> 100 nm (10-5 cm)
(3) Visibility	particles are not visible even with a powerful microscope	Particles can be seen with a high power microscope	particles can be seen with naked eyes
(4) Stability	Stable	Stable	Unstable
(5) Diffusion	Diffuse rapidly	Diffuse slowly	Do not diffuse
(6) Filterability	Pass through filter paper	passes through filter paper	can be separated by filter paper
Example	NaCI dissolved in water	Blood	Mud water.

Test of a colloidal solution or a suspension.
(i) A colloidal solution is turbid and the particle settles down on adding salt. In a suspension, particles settle down on keeping under the influences of gravity.
(ii) If the particles in a heterogeneous and opaque solution can be seen with naked eyes and get settled on keeping, then it is a suspension.

Various point of distinction between a chemical compound and a mixture are summarised below:

Characteristics	Pure substance or compound	Mixture
1. Composition	The elements in a compound are present in definite proportion by weight.	The ingredients of a mixture may be present in varying ratios.
2.Homogeneity	A compound is always homogeneous	A mixture may be homogeneous (solution) or heterogeneous.
3. Properties	A compound has entirely different properties from those of its constituents.	Properties of a mixture are an average of the properties of its constituents.
4. Separation	The constituents of a compound cannot be separated by simple separation techniques.	The constituents of a mixture can be separated by simple methods.
5. Energy changs	Energy in the form of heat, light, or electricity is either evolved or absorbed when a compound is formed	There is generally no energy change when a mixture is formed from its constituents.
6. volume change	At constant temperature and pressure, the formation of a compound may involve either no change or a large change in volume.	At constant temperature and pressure, the formation of a mixture involves either very little or no change in volume.

Homogeneous mixtures
(a) Solid solution. Alloys, e.g., brass, steel, bronze.
(b) liquid solution. Sugar solution in water, seawater, alcohol in water.
(c) Gaseous solution. Air, natural gas.
Heterogeneous mixtures
(a) Solid + Solid Sugar and sand, iron filings and sulphur, copper sulphate and potassium permanganate
(b) Solid +  Liquid Pastes, suspensions, etc.
(c) Solid + gas Smok
(d) Liquid + Liquid Milk, emulsions.
(e) liquid + Gas Soap bubbles.

The given mixture cannot be a solution because a solution is always homogeneous, if this is left undisturbed for some time and no solid settle down, then it is colloid otherwise it is suspension.

Solute in tincture of iodine: iodine
Solvent in tincture of iodine: ethanol
Tyndall effect is not seen in true solution because light passes through true solution unnoticed. particles of true solution are not able to scatter light to make its path visible.

True solution obtained in water are aqueous soliution, e.g., vinegar. true solutions in organic liquids like alcohol, acetone, etc. are non-aqueous solution, e.g., amino acids dissolved in acetone etc.

(a) Hydrogen gas
(b) Hydrogen sulphide
(c) In (a) iron reacts with dil. H2SO4 gas.
In (b) iron sulphide compound formed reacts with dil. H₂SO₄ to give H₂S gas.

Water is a compound because:
(i) The composition of hydrogen and oxygen in water taken from any source is the same.
(ii) The properties of water are different from that of its constituents, i.e., H₂ or O₂.

A compound is a substance which is formd by the combination of two or more elements in a fixed proportion by weight. The properties of a compound are entirely different from its constituent. A compound can be decomposed into two or more simpler substances. For example, water is a compound formed by combination of 89% oxygen and 11% hydrogen by weight irrespectively of its source. Its properties namely, density, physical state, reactivity etc. are quite different from the properties of hydrogen and oxygen. Water can be oxygen, salt is made of sodium and chlorine and sugar is made of carbon, oxygen and hydrogen having their constituent elements in fixed proportions. Carbon dioxide, salt and sugar are compounds.

Physical change. it is a temporary change in which the composition and chemical nature of the substance remains the same but the state of the substance and physical change. For example, when ice changes into water and water changes into vapours. The different states have differnt appearance and display different physical properties but they are chemically same.
Chemical change. A chemical change is a permanent change in which not only physical properties but chemical properties also change. This is because new substance/s is formed in a chemical change. Burning of candle is a chemical change. here both the physical and chemical change are taking place and new substance are formed.

Separation of components of a mixture is done for the following purpose
(i) to remove an undesirable component such as stones etc., as e.g., from wheat, rice.
(ii) To remove harmful components such as insects from grains or insects and other soluble impurities from water.
(iii) to obtain a pure sample of a substance.
(iv) To obtain a useful component such as butter from milk or gur from sugarcane.

Given, mass of solute = 110 g
Mass of solution = 550 g
% composition = \({110 \over 550}\times 100 \) 
Concentration = 20% by mass.

Homogeneous mixture Heterogeneous mixture (i) it has no visible boundary or boundaries of separation between its constituents. (i) It has visible boundary/boundaries of separation between its constituents. (ii) It has a uniform composition throughout its mass. (ii) The composition of the mixture varies from mass to mass (iii) It does not show the Tyndall effect (iii) It shows the Tyndall effect.

Mass of silver (Ag) ornament = mg
Mass of gold used for polishing = \(\frac{1}{100}\times\) mg = 0.01 mg
Atomic mass of Ag = 108 u
\(\therefore\) 1 mole of Ag = 108 g = 6.022 x 10²³ atoms
Thus, 108 g of Ag have atoms = 6.022 x 10²³
\(\therefore\) mg of Ag have atoms = \(\frac{6.022\times 10^{23}}{108}\)
Similarly, atomic mass of gold (Au) = 197 u
1 mole of Au = 197 g = 6.022 x 10²³ atoms
Thus, 197 g of Au have atoms = 6.022 x 10²³
\(\therefore\) 0.01 mg of Au will have atoms = \(\frac{6.022\times 10^{23}\times 0.01\ m}{197}\)
\(\therefore\) Ratio of the number of atoms of gold and silver = \(\frac{6.022\times 10^{23}}{197}\times 0.01\ m; \frac{6.022\times 10^{23}}{108}m\)
= \(\frac{1}{19700}:\frac{1}{108}\) 
= 108: 19700