Chapter : 2 Is Matter Around Us Pure?

Matter : Anything that occupies space and have mass .

There are two type of matter:

Pure and Mixture

Pure: A pure substance consists of a single type of particles.

There are two types of pure substance :

Elements: The elements are regarded as the building block of the universe cannot be broken down two similar substance. Metal , Non-metal and metalloids are the type of elements.

Compounds: Have fixed composition and can be broken down into electrochemical reaction. example, water, carbon dioxide sugar, etc.

Mixture: consists of two or more pure substance (element and compound).

There are two types of mixture :

(a) Homogeneous : A mixture is said to be homogeneous mixture if it has the the same composition throughout the sample. example, sugar in water, salt in, water, etc.

(b) Heterogeneous : A mixture is said to be heterogeneous mixture if it consists of a two or more part which have different composition. example, sand and salt, iron filling and sulphu, etc.

Properties of compounds :

The main properties of compounds are given below:

(1) Chemical compound consists of a two or more element combined together in a fixed proportion by mass.

(2) The properties of a compound are entirely different from those of its constituent element.

(3) A compound is a heterogeneous substances.

(4) A compound has a fixed melting point and boiling point.

(5) The constituent element of a compound cannot be separated by mechanical physical methods.

Properties of Mixture:

The mixtures generally have the following properties:

(1) The mixture may be homogenous or heterogeneous.

(2) The composition of the mixture is not fixed and is variable.

(3) The mixture does not have the definite melting point or boiling point.

(4) The properties of a mixture are the properties of its component.

(5) The formation of a mixture is not accompanied by any change in heat.

What is solution?
Solution is homogenous mixture of two or more substances.

A solution is generally made up of two components :

(a) Solvent: Component which is present in large amount is called solvent.

(b) Salute: The component which is present in lesser amount is called solute.

Aqueous and Non-aqueous Solutions:

(a) Aqueous solution: The solution of obtained by dissolving various substances in water are called aqua solution. Examples, salt water.

(b) Non- aqueous solution: The solution obtained by dissolving a substance in liquid other than water are called non aqueous solution. Example, I2 in CCl4.

Properties of solution:

The important properties of solution are:

(1) A solution is homogeneous in nature. It may be noted that in a solution there is homeogeneity at micro level.

(2) The size of particle of solution is less than 10-9 m, therefore they cannot be seen with naked eyes.

(3) The particle of a solution cannot be seen even with the help of a microscope.

Expressing concentration of a solution :

There are many ways of expressing concentration of a solution. The simplest method of expressing concentration of a solution is the amount of solute present in a given amount of solution.

Concentration = Amount of solute \ Amount of solution

It may also be expressed as the amount of solute dissolve in a given amount of solvent .

Concentration = Amount of solute / Amount of solvent

There are two common ways :

(1) Mass percentage: The simplest ways of expressing concentration of solution is mass percentage of solution. It gives mass of solute per 100 mass unit of solution. This may be expressed as:

Mass percent of solute = Massof Solute / Mass of Solution * 100

(2) Volumepercentage: If a solution is prepared by dissolving a liquid solute in a liquid solvent, then concentration may also be expressed as volume presentage of solute or percentage by volume present. This means the volume of solute in milliliters present in 100 milliliters of the solution.

Concentration of solution in percent= Volume of solute / Volume of solution * 100

Saturated and Unsaturated Solution :

(1) Saturated solution: A solution in which no more solute can be dissolved at a given temperature is called saturated solution.

(2) Unsaturated solution: A. solution in which the amount of solute is less than the saturation level is called unsaturated solution

Solubility: the amount of solute which can be dissolved in hundred gram of solvent at a given temperature is called its solubility.

What is suspension?
Suspension is a heterogeneous mixture in which the solid particles does not dissolve but remain suspended through out the bulk of the solvent.

Properties of suspension:

The main properties of suspension are:

(1) suspension is a heterogeneous mixture.

(2) the particle of suspension are bigger than 10 – 7 in diameter.

(3) the suspension can be separated from the mixture by the process of filtration.

What is colloidal solution?
A colloidal solution is a solution in which the size of a solid particle is intermediate between those in true solution and suspension.

(1) Dispersed phase: It is a component which is present in small proportion and concept of particle Collider dimension.

(2) Dispersion medium: It is the component which is present in Axis and acts as a median in which colloidal particles are dispersed.

Properties of Colloidal:

(1) Colloidal is a heterogeneous mixture. it consists of dispersed phase and dispersed medium

(2) The size of particle of a colloidal is in between 1nmand 100 nm.

(3) The particle Collpics are too small to be seen by naked eyes.

Separating the components of a mixture:

  1. How to obtain coloured component from blue or black ink?
    the coloured component can be obtained from blue or black ink by process of evaporation.
  2. How to separate cream from milk?
    the method of separating the solid particles suspended in liquid is called centrifugation.
  3. How to separate a mixture of two immiscible liquids?
    the image of liquid can be separated by separating funnel.
  4. How to separate a mixture of common salt and ammonium chloride?
    a mixture of common salt and ammonium chloride can be separated by the process of sublimation.
  5. How to separate a mixture of two immiscible liquids?
    emission of images liquid can be separated by the process of distillation.
  6. How to obtain gas from air?
    air is a homogeneous mixture of many gases the gases can be separated from air by fractional distillation. Physical and chemical change:

(1) Physical change the change in which the physical properties of a substance change but no new substance is formed are called physical change

(2) Chemical change the change in which new substances are formed are called chemical change.

Intext questions:

  1. What is meant by a pure substance?

Ans. A pure substance consists of a single type of particles.

  1. List the point of difference between homogeneous and heterogeneous mixture.

Ans. Homogeneous mixture:

(a) They have uniform composition throughout.
(b) They have same properties throughout the bulk.

Heterogeneous mixture:

(a) They do not have uniform composition throughout.
(b) They do not have same property throughout the bulk.

  1. Difference between homogeneous and heterogeneous mixture with examples.

Ans. In the question number 2 of Intex questions

Homogeneous mixture: Sodium chloride dissolve in water etc.

Heterogeneous mixture: Chalk mix in water etc.

  1. How are Sol, Solution and Suspension different from each other.

Ans. Sol:

(a) This nature is heterogeneous.
(b) Particle size between 1 to 100 nm.
(c) Diffusion is transparent.
(d) Tyndall effect is show.

True Solution:

(a) Its nature is homogeneous.
(b) Particle size between less than 1 nm.
(c) Diffusion is rapidly.
(d) Tyndall effect do not show.

Suspension:

(a) This nature is heterogeneous.
(b) Particle size more than 100 nm.
(c) Do not diffuse.
(d) Tyndall effect may or may not show.

  1. To make a saturated solution, 36 gram of sodium chloride is dissolved in100 gram of water at 293 K. Find its concentration at this temperature.

Ans. Its concentration is 36% by mass at 293 K.

  1. How will you separate a mixture of containing kerosene and petrol which are miscible with each other.

Ans. The mixture containing two liquids which are miscible with each other and have a boiling point different of more than 25 degree Celsius, these can be separated by distillation method.

  1. Name the technique to separate

(a) Butter from curd.
(b) Salt from seawater.
(c) Camphor from Salt.

Ans. (a) Centrifugation.
(b) Evaporation.
(c) Sublimation.

  1. What type of mixture are separated by the technique of crystallization?

Ans. It is used to separate a mixture of those two components in which one dissolve in a given solvent but the other remains insoluble.

  1. Classify the following as chemical or physical change:

(a) Cutting of trees.
(b) Melting of butter in Pan.
(c) Rusting of almirah.
(d) Boiling of water to form stem.
(e) Passing electric current through water and the water breaking down into hydrogen and oxygen gases.
(f) Dissolve in common salt in water.
(g) Making a fruit salad with draw fruit.
(h) Burning of paper and wood.

Ans. (a) Physical change.
(b) Physical change.
(c) Chemical change.
(d) Physical change.
(e) Chemical change.
(f) Physical change.
(g) Physical change.
(h) Chemical change.

Textbook Exercise:

  1. Which separation technique will use to apply for the separation of the following?

(a) Sodium chloride from its solution in water.
(b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride.
(c) Small piece of metal in the engine oil of a car.
(d) Different pigments from extract of flower Petals.
(e) Butter from curd.
(f) Oil from water.
(g) Tea leaves from tea
(h) Iron pins from sand.
(I) Wheat grain from husk.
(j) Fine mud particles suspended in water.

Ans. (a) Evaporation.
(b) Sublimation.
(c) Filtration.
(d) Chromatography.
(e) Centrifugation.
(f) Separating funnel.
(g) Filtration.
(h) Magnetic separation.
(I) Winnowing.
(j) Filtration.

  1. Write the steps you would use for making tea use the words solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.

Ans. step 1: Boil some water (solvent) in a pan.
Step 2: Put some tea live (solute) in a tea pot.
Step 3: Pour the boiling water into the port and let it soak for a few minutes. it will from a solution.
Step 4: Put sugar (solute) into a cup.
Step 5: stir the solution in the tea pot.
Step 6: Use are strainer and pour the solution into the cup put 2 spoon of milk. Remove the strainer and stir with a spoon. The tea is ready . The tea leaves (residue) will be left on the strainer while (filtrate) will pass through the solution. Shgar and milk are salute salute while tea leaves are insoluble salute.

  1. Explain the following by giving examples:

(a) Saturated solution.
(b) Pure substance.
(c) Colloid.
(d) Suspension.

Ans. (a) Saturated solution : A solution in which no more solute can be dissolved in the water.
For example : heat about hundred ml of water in a beaker to about 25 degree Celsius dissolve sodium chloride in this water gradually, until no more sodium chloride goes into the solution maintain the solution at 25 degree Celsius in the water bath the supper mental solution in the saturated solution of sodium chloride in water at 25 degree Celsius.

(b) Pure substance : a substance made up of only one type of particle.
For example : Distilled water.

(c) Colloid : a substance is said to be a collide if its particle size between 1 to100 nm.
For example : milk, gum etc.

(d) Suspension: it is a heterogeneous mixture in which the particle of a solute do not dissolve but remains stand throughout the bulk of a solvent
For example chalk powder in water

  1. Which of the following as a homogeneous and heterogeneous mixture.

Soda water, wood, air, soil, vinegar, filtered tea.

Ans. Soda water = Homogeneous mixture
Wood = Heterogeneous mixture
Air = Homogeneous mixture
Vinegar = Homogeneous mixture
Filtered tea = Homogeneous mixture

  1. How would you confirm that a colourless liquid given to you is pure water?

Ans. We can confirm that the colourless liquid given to us in pure water by checking its boiling point. Pure water will boil at 373 k at normal atmospheric pressure but water containing some salt will boil over a range of temperature of 373 K.

  1. Which of the following material falls in the category of “pure substance” ?

(a) Ice
(b) Milk
(c) Iron
(d) Hydrochloric acid
(e) Calcium oxide
(f) Mercury
(g) Brick
(h) Wood
(I) Air

Ans. (a) Ice, (c) Iron, (d) Hydrochloric acid, (f) Mercury
All are pure substance.

  1. Identify the solution among the following mixtures.

(a) Soil
(b) Sea water
(c) Air
(d) Coal
(e) Soda water.

Ans. (b) Sea water, (e) Soda water
Are solutions.

  1. Which of the following will show “tyndall effect” ?

(a) Salt solution
(b) Milk
(c) Copper sulphate solution
(d) Starch solution.

Ans. (b) Milk, (d) Starch all are show Tyndall effect.

  1. C,lassify the following into element, compound and mixture:

(a) Sodium
(b) Soil
(c) Sugar solution
(d) Silver
(e) Calcium carbonate
(f) Tin
(g) Silicon
(h) Coal
(I) Air
(j) Soap
(k) Methane
(l) Carbon dioxide
(m) Blood

Ans. a) Sodium = element
(b) Soil = mixture
(c) Sugar solution = mixture
(d) Silver = element
(e) Calcium carbonate = compound
(f) Tin = element
(g) Silicon = element
(h) Coal = mixture
(I) Air = mixture
(j) Soap = mixture
(k) Methane = compound
(l) Carbon dioxide = compound
(m) Blood = mixture

  1. Which of the following are chemical changes:
    (a) Growth of plant
    (b) Rusting of iron
    (c) Mixing of iron filling and sand
    (d) Cooking of food
    (e) Digestion of food
    (f) Freezing of water
    (g) Burning of a candle

Ans. Rusting of iron, Cooking of food, Digestion of food and Burning of candle are chemical changes.

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