Science Chapter 2: Is Matter Around Us Pure?
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Questions and Answers

Which of the following are chemical changes? (Select all that apply)

  • Burning of a candle (correct)
  • Rusting of iron (correct)
  • Growth of a plant
  • Cooking of food (correct)
  • Mixing of iron filings and sand
  • Freezing of water
  • Digestion of food (correct)

    • What is sodium?

    A chemical element with the symbol Na and atomic number 11.

    What is soil?

    A thin layer of material on the earth's surface made up of organic and inorganic substances.

    What is a sugar solution?

    <p>A mixture of sugar dissolved in water.</p> Signup and view all the answers

    What is silver?

    <p>A chemical element with the symbol Ag and atomic number 47.</p> Signup and view all the answers

    What is calcium carbonate?

    <p>A chemical compound with the formula CaCO3.</p> Signup and view all the answers

    What is tin?

    <p>A chemical element with the symbol Sn and atomic number 50.</p> Signup and view all the answers

    What is silicon?

    <p>A chemical element with the symbol Si and atomic number 14.</p> Signup and view all the answers

    What is coal?

    <p>A combustible black or brownish-black sedimentary rock.</p> Signup and view all the answers

    What is air?

    <p>A mixture of gases that make up the Earth's atmosphere.</p> Signup and view all the answers

    What is soap?

    <p>A substance used for cleaning, made from the salts of fatty acids.</p> Signup and view all the answers

    What is methane?

    <p>A chemical compound with the formula CH4.</p> Signup and view all the answers

    What is carbon dioxide?

    <p>A colorless gas with the formula CO2.</p> Signup and view all the answers

    What is blood?

    <p>A bodily fluid that delivers necessary substances to the body's cells.</p> Signup and view all the answers

    What is meant by a substance?

    <p>A substance refers to a form of matter that has a consistent composition and characteristic properties.</p> Signup and view all the answers

    List the points of differences between homogeneous and heterogeneous mixtures.

    <p>Homogeneous mixtures have a uniform composition throughout, while heterogeneous mixtures have distinct parts and non-uniform composition.</p> Signup and view all the answers

    What is a solution?

    <p>A solution is a homogeneous mixture of two or more substances.</p> Signup and view all the answers

    Solutions can only be in liquid form.

    <p>False</p> Signup and view all the answers

    What components make up a solution?

    <p>A solution is made up of a solvent and a solute.</p> Signup and view all the answers

    Which of the following is an example of a heterogeneous mixture?

    <p>Sand in water</p> Signup and view all the answers

    Define the term 'colloidal solution'.

    <p>A colloidal solution is a mixture in which very fine particles of one substance are dispersed in another without settling.</p> Signup and view all the answers

    What is the Tyndall effect?

    <p>The Tyndall effect is the scattering of light by the particles in a colloid.</p> Signup and view all the answers

    A __________ is a heterogeneous mixture in which solute particles do not dissolve but remain suspended.

    <p>suspension</p> Signup and view all the answers

    What happens to the solute particles in a suspension when left undisturbed?

    <p>They settle down</p> Signup and view all the answers

    What is mass by mass percentage of a solution?

    <p>Mass by mass percentage is calculated as (Mass of solute / Mass of solution) × 100.</p> Signup and view all the answers

    Differentiate between homogeneous and heterogeneous mixtures with examples.

    <p>A homogeneous mixture has a uniform composition (e.g., saltwater), while a heterogeneous mixture has a non-uniform composition (e.g., salad).</p> Signup and view all the answers

    How are sol, solution, and suspension different from each other?

    <p>A sol is a colloidal system where solid particles are dispersed in a liquid, a solution is a homogeneous mixture of solute and solvent, and a suspension contains larger particles that can settle out.</p> Signup and view all the answers

    Find the concentration of a saturated solution when 36 g of sodium chloride is dissolved in 100 g of water at 293 K.

    <p>The concentration is 36 g of sodium chloride in 100 g of water.</p> Signup and view all the answers

    Which type of colloid is described as fog, clouds, and mist?

    <p>Aerosol</p> Signup and view all the answers

    What is a characteristic of metals?

    <p>They are malleable</p> Signup and view all the answers

    An element can be broken down into simpler substances by chemical reactions.

    <p>False</p> Signup and view all the answers

    Which of the following is an example of a pure substance?

    <p>Ice</p> Signup and view all the answers

    Which gas is obtained when Group I mixes and crushes iron filings and sulphur powder?

    <p>Hydrogen</p> Signup and view all the answers

    What is a compound?

    <p>A compound is a substance composed of two or more elements chemically combined in fixed proportions.</p> Signup and view all the answers

    The major component of a solution is called the ______.

    <p>solvent</p> Signup and view all the answers

    Which of the following materials is a liquid at room temperature?

    <p>Hydrochloric acid</p> Signup and view all the answers

    Which of the following will show the Tyndall effect?

    <p>Milk</p> Signup and view all the answers

    How would you confirm that a colorless liquid is pure water?

    <p>Test for its boiling and freezing points, which should be 100°C and 0°C, respectively.</p> Signup and view all the answers

    Study Notes

    Understanding Pure Substances and Mixtures

    • Milk, ghee, butter, salt, spices, and juices are not pure substances; they are mixtures containing different components.
    • Pure substances have a uniform and consistent composition throughout and cannot be separated into simpler substances via physical methods.
    • Examples of pure substances include sugar, which consists of only one kind of material.

    Types of Mixtures

    • Mixtures can be classified based on component characteristics and can be homogeneous or heterogeneous.
    • Homogeneous mixtures (solutions) have uniform composition; the components cannot be distinguished. Examples include sugar in water and salt in water.
    • Heterogeneous mixtures have visibly distinct parts and non-uniform composition. Examples include sand and iron filings, or oil and water.

    Solutions

    • A solution is a homogeneous mixture of two or more substances that retains uniform properties.
    • Solutions consist of solute (substance being dissolved) and solvent (substance that dissolves the solute).
    • Examples include lemonade (sugar as solute, water as solvent) and air (mixture of gases).

    Properties of Solutions

    • Solution particles are smaller than 1 nanometer and cannot scatter light; hence, their path is not visible.
    • Solutions are stable, meaning solute particles do not settle out upon standing.
    • The concentration of solutions can be expressed in mass/volume or volume/volume percentages.

    Suspensions

    • Suspensions are heterogeneous mixtures where solute particles are suspended but not dissolved in a solvent.
    • The particles in a suspension are larger than those in solutions and can scatter light, making their path visible (Tyndall effect).
    • Suspensions can be separated via filtration due to their larger particle size.

    Colloidal Solutions

    • Colloids consist of fine particles dispersed in a medium, appearing homogeneous despite being heterogeneous at the microscopic level.
    • Colloids can scatter light and show the Tyndall effect, distinguishing them from true solutions.
    • Colloidal mixtures can be separated using centrifugation, not filtration.

    Examples of Colloids

    • Classified by their composition like aerosols (fog), emulsions (milk), foams (shaving cream), gels (jelly), and solid sols (colored gemstones).

    Concentration of Solutions

    • Concentration can be expressed through mass by mass, mass by volume, and volume by volume percentages.
    • The solubility of a substance is the maximum amount that can dissolve in a specified amount of solvent at a given temperature.

    Physical and Chemical Changes

    • Physical changes involve alterations in the state or appearance without changing the chemical composition, such as dissolving sugar in water.
    • Chemical changes involve the transformation of substances, which may result in new materials being formed, like during combustion.### Physical Properties of Matter
    • Physical properties include color, hardness, rigidity, fluidity, density, melting point, and boiling point.
    • Interconversion of states (e.g., ice to water to water vapor) is a physical change, preserving chemical composition.

    Elements

    • Element defined by Antoine Lavoisier as a basic form of matter, irreducible by chemical reactions.
    • Elements categorized as metals, non-metals, and metalloids.
    • Characteristics of metals:
      • Lustrous appearance (shine).
      • Silvery-grey or golden-yellow colors.
      • Good conductors of heat and electricity.
      • Ductility and malleability (can be drawn into wires or hammered into sheets).
      • Sonorous (produce a ringing sound).
    • Examples of metals: gold, silver, copper, iron, sodium, potassium; mercury is liquid at room temperature.

    Non-Metals

    • Non-metals have varied colors and poor conductivity of heat and electricity.
    • Non-metals are non-lustrous, not sonorous, and are often not malleable.
    • Examples of non-metals: hydrogen, oxygen, iodine, carbon, bromine, chlorine.

    Metalloids

    • Elements with properties intermediate between metals and non-metals.
    • Examples include boron, silicon, and germanium.

    Compounds

    • Compounds consist of two or more elements chemically combined in fixed proportions.
    • Properties of compounds differ significantly from their constituent elements.
    • Distinction from mixtures:
      • Mixtures retain the properties of their constituents.
      • Compounds have fixed, unique properties.

    Solutions and Mixtures

    • Solutions are homogeneous mixtures where the major component is the solvent, and the minor component is the solute.
    • Suspensions are heterogeneous mixtures with visible particles, while colloids have small particles that scatter light.
    • Examples of separation methods:
      • Evaporation for separating salt from water.
      • Filtration for separating solids from liquids.

    Key Concepts

    • Pure substances can be either elements or compounds, with elements being indivisible by chemical means and compounds having distinct properties from their components.
    • Mixtures can be separated into pure components through physical means, demonstrating variable compositions.

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    Chapter 2: Is Matter Around Us Pure? (Science PDF)

    Description

    Dive into Chapter 2 of your science curriculum, exploring the concept of purity in matter. This quiz will challenge your understanding of pure substances and their characteristics, including examples like milk, ghee, and sugar. Test your ability to differentiate between pure and impure matter and grasp the principles behind their classification.

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