9th Class Science Is Matter Around Us Pure Mixture

        Introduction

 

In our daily life we come across several types of matters in our surroundings. It is very difficult to say which of the matters is pure. Even the eatables, which we purchase from the market is not found to be pure and is adulterated with undesirable materials that are harmful for us. The pure substance is the substance which are made up of only one type of atoms or particles. All the matters are divided into two categories as mixture and pure substance.

 

            Mixture

When two or more different types of substance are mixed together, not in any fixed proportion, it is called mixture. Mixture is of two types Homogenous and heterogenous mixtures. In mixtures the components cannot be separated by physical means.

 

            Homogenous Mixture

The mixture having uniform composition is called the homogenous mixture. If we dissolve sugar or salt in water, it gets dissolved completely in water and particles of sugar are not visible to us our naked eyes. Hence it is a homogenous mixture. It has no visible boundaries of separation between various constituents and usually exist in one phase.

 

(1) Air is a mixture of gas in gas.

(2) Aerated water \[(C{{O}_{2}}+{{H}_{2}}O)\] is a mixture of gas in liquid.

(3) Kerosene, petrol, alcohol, water, etc are mixture of liquid in liquid.

(4) Alloys such as bronze, steel, brass etc are mixture of solid in solid.

(5) Sugar solution, salt solution are mixture of solid in liquid.

(6) Amalgamated Zinc is a mixture of liquid in solid.

(7) Adsorption of hydrogen gas in palladium is a mixture of gas in solid.  

 

            Heterogenous Mixture

The mixture having non uniform composition are called heterogenous mixture. In this case, each constituent particles are visible in our naked eyes. We can separate them by physical means. For example if we mix rice, sand and pulse the mixture will be heterogenous and each constituent is visible in our naked eyes and we can separate them either by hand picking or any other means.

 

            Properties of Mixture

Following are the properties of mixtures:

• The constituents in the mixtures are not present in any fixed proportion.
• Each constituents in the mixture shows it own properties.
• The constituents of the mixtures can be separated by physical methods.
• Mixtures do not have any fixed melting and boiling points.
• No energy is either absorbed or evolved during the formation of mixtures.

 

 

 

 

       Which one of the following is a homogenous mixture?

(a) Salt solution

(b) Muddy water

(c) Chalk in water

(d) All

(e) None of these

 

Answer: (A)

 

 

        Which one of the following is a heterogenous mixture?

(a) Steel

(b) Brass

(c) Smoke

(d) Air

(e) None of these

 

Answer: (C)

 

 

         Which one of the following is a mixture?

(a) Salt

(b) Water

(c) Sugar 

(d) Air

(e) None of these

 

Answer: (D)

 

 

       Which one of the following is most difficult to separate?

(a) Sawdust and stones

(b) Sand and Water

(c) Rice and pulse

(d) Nitrogen and Hydrogen

(e) None of these

 

Answer: (D)  

 

 

            Pure Substance

The substances which is made up of only one kind of particles are called the pure substance or we can say that the substance which is made up of only one kind of atoms are called the pure substance. For example, elements of oxygen, carbon, calcium, sodium chloride, etc are considered to be pure substance.  The pure substance have some specific properties, such as, they have definite colours like gold appears yellow, bromine gas is brown in color, iodine is violet in colour etc. Other properties are that they have fixed melting and boiling points. For example, water boils at 100°C and has a refractive index of 1.333 and density of 0.999 g/ml at 20°C. Pure ice melts at 0°C.

 

           Properties of Pure Substance

The properties of pure substance are:

• It has certain fixed density.
• It has fixed melting and boiling points.
• Refractive index can be measured accurately.
• They are either conductors, insulators or semiconductor.
• Normally have high viscosity.

 

          Types of Pure Substance

Pure substance is normally of two types: element and compound. The elements are further classified as metals, non metals and metalloid. Elements: The first defination of elements was given by Robert Byoles in the year 1661 in Britain. According to him, element is the simplest form of the matter and cannot be further simplified and broken into simpler pieces. The elements are further classified as metals, non metals and metalloids.

 

            Properties of Metals

Following are the properties of metals:

• Metals are generally solid at room temperature, except for mercury.
• Metals are lustrous.
• Metals have normally golden yellow or silver grey colours.
• Metal are generally good conductor of electricity, except for lead and mercury, which are poor conductor of electricity. Silver is the best conductor of electricity.
• Metals are generally hard, except for sodium and potassium.
• Metals have generally high tensile strength.
• Metals have generally high melting and boiling points except for mercury, sodium, gallium and potassium.
• Metals are malleable and ductile.
• Metals are sonorous.

 

            Properties of Non-Metals

• It exist in all the three states at normal temperature and pressure. The nonmetal like sulphur, carbon, and phosphorus are found in solid states; non metal like bromine is found in liquid states and oxygen, chlorine hydrogen are found in gaseous states.
• Non metals are generally soft except for diamond.
• Non metal are non lustrous except for iodine.
• Non metals are non sonorous and usually have low tensile strength.
• They have generally low melting and boiling points, except for graphite whose melting point is 3700°C.
• Non metals are poor conductor of heat and electricity except for diamond which is a good conductor of heat. Also graphite, which is good conductor of electricity. They are normally good insulators.
• They are founded in variety of colours, such as, bromine is red brown/sulphur is yellow, graphite is black, phophrous is red or white, chlorine is yellowish green in colour.
• They are neither malleable nor ductile.

 

             Metalloids

There are some elements, which show the properties of both metal and non metals. They are called the metalloids. For example the elements like boron, silicon, germanium, arsenic, antimony, etc. are metalloids.

 

 

 

 

        Name the metal which is founded in liquid form?

(a) Bromine

(b) Mercury

(c) Antimony

(d) Tin

(e) None of these

 

Answer: (b)

 

 

         Who give the first defination of elements?

(a) Robert Boyles

(b) Robert Charles

(c) Mendleev

(d) Bhors

(e) None of these

 

Answer: (a)

 

 

         Which one of the following is a Compound?

(a) Brass

(b) Steel

(c) Chlorine

(d) Carbon dioxide

(e) None of these

 

Answer: (d)

 

 

         Martin was given a mixture of benzene and methyl benzene and asked to separate the components of the mixture. Which one of the following method will he use?

(a) Decentation

(b) Sublimation

(c) Distillation

(d) Evaporation

(e) None of these

 

Answer: (c)

 

 

        Identify the pure substance from the given material.

(a) Calcium oxide

(b) Wood

(c) Air

(d) All

(e) None of these

 

Answer: (a)