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Class IX - Science: Is Matter Around Us Pure
One Word Answer Questions:
Q) When no more solute can be dissolved in a solution at a given temperature, it is called ?
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Q) When no more solute can be dissolved in a solution at a given temperature, it is called which solution?
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Q) Which pair is a miscible liquid mixture?
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Short Answer Questions:
Q) Mixtures are constituted by more than one kind of pure form of matter, known as ?
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Q) What is a homogeneous mixture of two or more substances ?
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Q) If the amount of solute contained in the solution is less than the saturation level, it is called ?
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Q) What is the formula for Concentration of a Solution ?
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Q) What is saturated solution?
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Q) What is unsaturated solution?
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Q) What is suspension?
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Q) What is Colloidal Solution?
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Q) What is Mixture?
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Q) Give one example of a metal?
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Q) Lesser quantity of component is called?
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Q) To make a saturated solution, 36 g of sodium chloride is dissolved in 100g of water at 293 kelvin. Find its concentration at this temperature.?
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Q) Write a short note on Compounds?
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Q) What type of mixtures are separated by the technique of crystallization?
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Q) Write a short note on Physical And Chemical Changes?
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Long Answer Questions:
Q) Explain, what is Mixture and different types of mixture?
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Q) Explain, what is solution and properties of solution?
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Q) Difference between Saturated and Unsaturated Solution?
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Q) Difference between Mixtures and Compounds?
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Q) Explain different types Of Pure Substances?
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Q) How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25°C) which are miscible with each other?
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Q) How are sol, solution and suspension different from each other?
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Q) Explain the Concentration of a Solution?
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Is Matter Around Us Pure
  • For scientist all things are actually mixtures of different substances and hence not pure. For example, milk is actually a mixture of water, fat, proteins, etc.
  • When scientists says something pure, it means that all the constituent particles of that substances are the same in their chemical nature.
  • A pure substance consists of a single type of particles. In other words, a substance is a pure single form of matter.
What is Mixture ?
  • Mixtures are constituted by more than one kind of pure form of matter, known as a substance.
  • A substance cannot be separated into other kinds of matter by any physical process.
  • A mixture contains more than one substance.
Types of Mixtures

Depending upon the nature of the components that form a mixture, we can have different types of mixtures.

Activity 1
  • Let us divide the class into four groups A, B, C and D.
  • Distribute the following samples to each group
    1. Few crystals of copper sulphate to group A.
    2. One spatula full of copper sulphate to group B.
    3. Chalk powder or wheat flour to group C.
    4. Few drops of milk or ink to group D.
  • Each group should add the given sample in water and stir properly using a glass rod.
  • Put a direct beam of light from a torch through the beaker containing these mixtures and observe.
  • Later, the particles settle down.
  • Filter the mixture. Is there any residue on the filter paper?
  • You will get different results for each mixture.
  • Is Matter around us Pure
    Filtration
    What is A Solution ?
    • A solution is a homogeneous mixture of two or more substances.
    • For example, lemonade, in lemonade the particles of sugar and salt are evenly distributed in the solution.
    • Alloys are mixtures of two or more metals or a metal and a non-metal and cannot be separated into their components by physical methods.
    • Example, brass = 70% copper + 30% zinc.
    • A solution has a solvent and a solute as its components.
    • Larger amount of component is called solvent.
    • Lesser quantity of component is called solute.
    • Example, a solution of sugar in water is a solid in liquid solution. In this solution, sugar is the solute and water is the solvent.
    Properties of a Solution
    • A solution is a homogeneous mixture.
    • The particles of a solution are smaller cannot be seen by naked eyes.
    • They don't scatter the beam of light passing through the solution. So, the path of light is not visible in a solution.
    • The solute particles cannot be separated from the mixture by the process of filtration. The solute particles do not settle down when left undisturbed, that is, a solution is stable.
    Difference between Saturated and Unsaturated Solution
    Saturated solutionUnsaturated solution
    When no more solute can be dissolved in a solution at a given temperature, it is called a saturated solution.
    The amount of the solute present in the saturated solution at this temperature is called its solubility.
    If the amount of solute contained in the solution is less than the saturation level, it is called an unsaturated solution.

    Concentration of a Solution

    The concentration of a solution is the amount of solute present in a given amount of solute dissolved in a given mass or volume of solvent.
    Concentration of solution = amount of solute/amount of solution (Or) Amount of solute/amount of solvent

    1. Mass by mass percentage of a solution = Mass of solute/Mass of solution × 100
    2. Mass by volume percentage of a solution = Mass of solute/volume of solution × 100

    Example:
    A solution contains 50 g of sugar in 430 g of water. Calculate the concentration in terms of mass percentage of the solution.

    Solution:
    Mass of solute (sugar) = 50 g
    Mass of solvent (water) = 430 g
    Mass of solution = mass of solute + mass of solvent
    = 50 + 430
    = 480 g
    Mass percentage of solution = mass of solute/mass of solution × 100
    ⇒ 50 / 480 × 100 = 10.42 %

    What is a Suspension ?

    A suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the bulk of the medium. Particles of a suspension are visible to the naked eye.

    Properties of a suspension
    • Suspension is heterogeneous mixture.
    • The particles of a suspension can be seen by the naked eye.
    • The particles of a suspension scatter a beam of light passing through it and make its path visible.
    • The solute particles settle down when a suspension is left undisturbed.
    • They can be separated from the mixture by the process of filtration.
    What Is a Colloidal Solution ?
    • Solution in which the size of particles lies between those of true solution and suspensions are called colloidal solution or colloids.
    • Because of small size of colloidal particles, we cannot see them with naked eyes.
    • But, these particles can easily scatter a beam of visible light. This scattering of a beam of light is called the Tyndall effect.
    • Tyndall effect can also be observed when a fine beam enters a room through a small hole.
    • This happens due to the scattering of light by the particles of dust and smoke in the air.
    Is Matter around Us Pure
    (a). Solution of copper sulphate does not show Tyndall effect.
    (b). Mixture of water and milk shows Tyndall effect
    Properties of a colloids
    • A colloid is a heterogeneous mixture.
    • The size of particles of a colloid is too small to be individually seen by naked eyes.
    • Colloids are big enough to scatter a beam of light passing through it and make its path visible.
    • They do not settle down when left undisturbed.
    • Colloid is stable.
    • They cannot be separated from the mixture.
    Separating The Components Of a Mixture

    How can we obtain coloured component from Blue/Black Ink ?
    Activity 2

    • Fill half a beaker with water.
    • Put a watch glass on the mouth of the beaker.
    • Put few drops of ink on the watch glass.
    • Heat the beaker. You will see the evaporation is taking place.
    • Observe carefully after stopping heat after some time.
    • We will find that ink is a mixture of a dye in water.
    • Thus, we can separate the volatile component solvent from its nonvolatile solute by the method of evaporation.
    Is Matter around Us Pure
    Evaporation

    How can we separate Cream From Milk ?
    Activity 3

    • Take some full cream milk in a vessel.
    • Use a milk churner and churn it.
    • Sometimes the solid particles in a liquid are very small and pass through a filter paper.
    • For such particles, centrifugation method is done.
    • The principle is that the denser particles are forced to the bottom and the lighter particles stay at the top when spun rapidly.
    • This method is called centrifugation method.
    • Applications
    • Used in labs for blood and urine test.
    • Used in dairies and home to separate cream.
    • Used in washing machines to squeeze out water from wet clothes.

    How can we separate a mixture of two Immiscible Liquids ?
    Activity 4

    • Let us separate kerosene oil from water using a separating funnel.
    • Pour the mixture of kerosene oil and water in a funnel.
    • Let it stand undisturbed so that separate layers of oil and water are formed.
    • Open the stopcock of the funnel and pour out the layer.
    • Oil reaches the stopcock.
    • Is Matter around Us Pure
      Separation of Immiscible Liquids
    • The principle is that immiscible liquids separate out in layers depending on the densities.
    • Applications
    • To separate mixture of oil and water.
    • In the extraction of iron from its ore.

    How can we separate a mixture of Salt and Ammonium Chloride ?

    • Ammonium chloride changes directly from solid to gaseous state on heating.
    • So, to separate such mixtures that contain a sublimable volatile component from a non-sublimable impurity, the sublimation process is used.
    • Is Matter around Us Pure
      Separation of Ammonium Chloride and salt
      Applications
    • Uses for camphor, naphthalene and anthracene.
    • Uses for ammonium chloride.

    How can we separate a mixture of two Miscible Liquids ?
    Activity 5

    • Let us try to separate acetone and water from their mixture.
    • Take the mixture in the distillation flask. Fill it with a thermometer.
    • Heat the mixture slowly keeping a close watch at the thermometer.
    • The acetone vaporises, condenses in the condenser and can be collected from the condenser outlet.
    • Water is left behind in the distillation flask.
    • Is Matter around Us Pure
      Separation of two miscible liquids by distillation
    • This method is called distillation. It is used to separate mixtures containing two miscible liquids.
    • To separate a mixture of two or more miscible liquids for which the difference in boiling points is less than 25 K, fractional distillation is used.
    • For example, for the separation of different gases from air, different fractions from petroleum products.
    • The apparatus is similar to that for simple distillation, except that a fractionating column is fitted in between the distillation flask and the condenser.
    • A simple fractionating column is a tube packed with glass beads. The beads provide surface for the vapours to cool and condense repeatedly, as shown in diagram
    • Is Matter around Us Pure
      Fractional Distillation
    Different Gases From Air
    • Air is the homogeneous mixture and can be separated into its components by fractional distillation.
    • The flow diagram shows the steps of the process.
    • The air is compressed by increasing the pressure and is then cooled by decreasing the temperature to get liquid air.
    • This liquid air is allowed to warm up slowly in a fractional distillation column, where gases get separated at different heights depending upon their boiling points.
    • Is Matter around Us Pure

      Flow diagram shows the process of obtaining gases from air

      Is Matter around Us Pure

      Separation of Components of air
    Physical And Chemical Changes
    • The properties that can be observed and specific like colour, hardness, rigidity, melting point, etc. are the physical properties.
    • These changes occur without a change in composition and no change in the chemical nature of the substances.
    What Are The Types Of Pure Substances ?

    On the basis of their chemical composition, substances can be classified either as elements or components.

    Metals usually show some or all of the following properties:

    • They have a lustre(shine).
    • They have silvery-grey or golden-yellow colour.
    • They conduct heat and electricity.
    • They are ductile.
    • They are malleable.
    • They are sonorous.
    • Examples of metals are gold, silver, copper, iron, sodium, etc.
    • Mercury is the only metal that is liquid at room temperature.

    Non-metals usually show some or all of the following properties:

    • They display a variety of colours.
    • They are poor conductors of heat and electricity.
    • They are not lustrous, sonorous or malleable.
    • Examples of non-metals are hydrogen, oxygen, iodine, etc.
    • Some elements have intermediate properties between those of metals and non-metals, they are called metalloids. Examples are Boron, Silicon, Germanium, etc.
    Compounds

    A compound is a substance composed of two or more elements, chemically combined with one another in a fixed proportion.

    Mixtures and Compounds
    MixturesCompounds
    1. Elements or compounds just mix together to form a mixture and no new compound is formed.1. Elements react to form new compounds.
    2. A mixture has a variable composition.2. The composition of each new substance is always fixed.
    3. A mixture shows the properties of the constituent substances.3. The new substance has totally different properties.
    4. The constituents can be separated fairly easily by physical methods.4. The constituents can be separated only by chemical or electrochemical reactions.
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