9th Class Science Is Matter Around Us Pure Compounds

        Compounds

It is a pure substance, in which two or more elements combine chemically together in a fixed proportion by mass to form the compound. The properties of compound are different from the properties of the elements.

For example, the elements like hydrogen and oxygen are found in gaseous state, but when they combine to form water, it turns to liquid state. Similarly if we heat iron filing and sulphur powder, a black compound of iron sulphide is formed. Now, if we bring a bar magnet near the compound we find that it is not attracted by the iron in the compound so formed. The other example, if we add carbon disulphide to the sulphur, we find it is not dissolved in it, which shows that sulphur is not showing its property. Thus, we can say that the properties of compound is entirely different of the it’s elements forming it.

            Properties of Compound

Following are the properties of compound:

• It is formed by the reaction between two or more different elements.
• It is homogenous in nature.
• We cannot separate the components of compound by physical methods.
• The compounds have different physical and chemical properties.
• They have generally fixed melting and boiling points.
• Formation of compound is associated with either evolution or absorption of heat and light.

 Normally we have two types of compounds, that is, organic and inorganic compounds. Those compounds which are obtained from non living sources such as rocks, minerals, etc are inorganic compounds. The compounds which are obtained from living sources such as plants, animals etc are called organic compound. For example, petroleum, carbohydrates, proteins, waxes, oils, etc. are all organic compounds.

        Solutions

It is a homogenous mixture of two or more substance in which one substance is liquid. It consists of two parts, solvent and solute. The solvents are that part of solution in which something has been dissolved and the substance which has been dissolved into it, is called the solute. For example, in the solution of salt and water, salt is solute as it is dissolved in water and water is solvent.

The solution is basically of two types, such as saturated and unsaturated. Saturated solutions are those in which no more solute can be dissolved. On the other hand, the solution in which more solutes can be dissolved are called the unsaturated solution. The amount of solute present in the saturated solution at the given temperature is called its solubility.

The concentration of solution is defined as the amount of solute presents in the given volume of solvent.

Concentration of solution \[=\,\frac{Mass\,of\,solute}{Mass\,of\,solution}\]

Percentage by mass \[=\,\frac{Mass\,of\,solute}{Mass\,of\,solution}\times 100\]

Percentage by volume \[=\,\frac{Volume\,of\,solute}{Volume\,of\,solution}\times 100\]     

            Properties of Solution

• It is homogenous in nature.
• The particles of solute cannot be seen in naked eyes.
• They cannot scatter the beam of light passing through it.
• We cannot separate the particles of solute by physical methods, such as filtrations.
• It is very stable in nature i.e. the particles of solute do not settle down when left undisturbed.

              Suspension

It is a heterogenous mixtures in which particles of solute are dispersed throughout the medium, without dissolving into it. For example, if we mix sand in water it forms suspension, as the sand particles remains suspended in the water without dissolving into it.

             Properties of Suspension

• It is heterogenous in nature.
• The particles of solute can be seen in naked eyes.
• The particles of suspension can be separated by filtration.
• It is opaque in nature.
• It is very unstable in nature i.e. the particles of solute settles down when left undisturbed.

             Collodials

It is a heterogenous mixture in which particles having size between \[{{10}^{-7}}\] to \[{{10}^{-4}}\] cm are dispersed in a continuous medium. The continuous medium is called dispersion medium and the particle in the medium forms dispersed phase. They are also called as sols. If the dispersion medium is water then it is called hydrosols and if it is alcohol, it is called alcosols. Colloids can be classified on the basis of the affinity of dispersed phase and dispersion medium for each other. On the basis of this it is of two types: Lyophilic colloids and Lyophobic colloids.

The colloid which shows affinity towards the dispersion medium is called lyophilic colloids. For example, gelatin and starch are lyophilic colloids. The colloids which do not shows affinity towards the dispersion medium is called lyophobic colloids. For example, metals and their hydroxide and sulphide are lyophobic colloids.

            Properties of Colloids

• It is heterogenous in nature.
• The particles of colloids cannot be seen by naked eyes.
• The particles of colloids cannot be separated by filtration.
• The particle of colloids shows Brownian motion.
• It is very unstable in nature i.e. the particles of solute settles down when left undisturbed.
• It shows tyndall effect i.e. it scatters the beam of light passing through it.
• It shows electrophoresis. i.e. it shows the movement of particles under the influence of electric field towards the opposite charged electrodes.
• It shows the coagulation i.e. the colloidal particles precipitate and settles down if all the charge is removed from it. It can be done by adding oppositely charged electrolytes.

       Which one of the following will show tyndall effect?

(a) Salt solution

(b) Milk

(c) Sulphuric acid solution

(d) HCI

(e) None of these

Answer: (b)

       Which one of the following will show the properties of electrophoresis?

(a) Arseneous Sulphide

(b) Carbon dioxide

(c) Chalk in water

(d) Hydrosoles

(e) None of these

Answer: (a)

       A solution is prepared by dissolving 80 g of salt in 500 g of water. Find the concentration of the solution.

(a) 10%

(b) 12.6%

(c) 13.8%

(d) 14.2%

(e) None of these

Answer: (c)

       Which one of the following is an aerosols?

(a) Mist

(b) Vapour

(c) Egg Yolk

(d) Sugar solution

(e) None of these

Answer: (a)

       If 10 g of sodium hydroxide is dissolved in 150 g of water, then calculate the mass percent of sodium hydroxide in the solution?

(a) 5%

(b) 6.25%

(c) 7.5%

(d) 8.2%

(e) None of these

Answer: (b)

        If \[30\,C{{M}^{3}}\] of aldehyde is added to water to make its volume of \[363\,c{{m}^{3}}\], then find the percentage of volume of aldehyde in this solution.

(a) 9.1% 

(b) 7.96%

(c) 8.26%

(d) 6.65%

(e) None of these

Answer: (c)