Elements, Compounds & Mixtures Quiz
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Questions and Answers

What is the first substance to evaporate during fractional distillation of a mixture of water and ethanol?

  • Water
  • Ethanol (correct)
  • Both Evaporate Simultaneously
  • None of the Above

    • Fractional distillation can be used to separate liquids that are not miscible.

    False

    At what temperature should heating be stopped during the fractional distillation of ethanol and water?

    100 ºC

    The boiling point of ethanol is _____ ºC.

    <p>78</p> Signup and view all the answers

    Match the following components with their properties:

    <p>Ethanol = Boiling point of 78 ºC Water = Boiling point of 100 ºC Condenser = Cools vapors into liquid Fractional Distillation = Separates miscible liquids</p> Signup and view all the answers

    Which of the following is NOT a characteristic of an element?

    <p>It can be chemically combined with other elements.</p> Signup and view all the answers

    A compound can be separated into its elements by physical means.

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

    What defines a compound?

    <p>A pure substance made up of two or more elements chemically combined.</p> Signup and view all the answers

    An example of a _____ is sand and water.

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

    Match the substance to its classification:

    <p>Copper = Element Carbon Dioxide = Compound Salt Water = Mixture Iron = Element</p> Signup and view all the answers

    What type of substance can be separated by filtration?

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

    There are 118 elements listed in the Periodic Table.

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

    What is the main difference between a compound and a mixture?

    <p>A compound is chemically combined while a mixture is not.</p> Signup and view all the answers

    What is the primary purpose of filtration?

    <p>To separate an undissolved solid from a liquid</p> Signup and view all the answers

    Crystallisation can be used to separate a solid that is less soluble in hot solvent than in cold.

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

    What indicates that a solution has reached saturation during the crystallisation process?

    <p>Crystals form on a glass rod dipped into the solution.</p> Signup and view all the answers

    In filtration, the solid particles remain as a ______ while the liquid that passes through is called ______.

    <p>residue; filtrate</p> Signup and view all the answers

    Match the following processes with their correct descriptions:

    <p>Filtration = Separation of undissolved solids from liquids Centrifugation = Separation of mixtures using high speed Crystallisation = Separation of dissolved solids from solutions Evaporation = Conversion of liquid to vapor to leave solids behind</p> Signup and view all the answers

    What is the first step in the process of crystallisation?

    <p>Heating the solution to evaporate the solvent</p> Signup and view all the answers

    During crystallisation, crystals grow as the solubility of the solid increases.

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

    What is done to the crystals after they are collected from the saturated solution?

    <p>They are washed with cold distilled water and allowed to dry.</p> Signup and view all the answers

    What is the primary purpose of paper chromatography?

    <p>To separate substances based on their solubilities</p> Signup and view all the answers

    In paper chromatography, the pencil line must be submerged in the solvent.

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

    What causes the different substances to separate during paper chromatography?

    <p>Different solubilities in the solvent.</p> Signup and view all the answers

    In paper chromatography, substances with higher solubility will travel ______ than those with lower solubility.

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

    Which technique is used to separate a soluble solid like sodium chloride from a solution?

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

    Match the term with its correct definition:

    <p>Chromatography = Technique for separating substances based on solubility Capillary action = Movement of solvent up the paper Soluble solid = Solid that dissolves in a solvent Evaporation = Process of turning liquid into vapor</p> Signup and view all the answers

    Different inks will travel the same distance when subjected to paper chromatography.

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

    Why is a pencil line preferred over an ink line in chromatography?

    <p>Ink would run into the chromatogram and mix with the samples.</p> Signup and view all the answers

    What does an Rf value indicate?

    <p>The retention factor of a substance</p> Signup and view all the answers

    The Rf value of a compound remains the same regardless of the solvent used.

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

    What is the formula to calculate the Rf value?

    <p>Rf = distance moved by substance / distance moved by solvent</p> Signup and view all the answers

    The maximum possible Rf value is ______.

    <p>1</p> Signup and view all the answers

    Which statement about Rf values is false?

    <p>Rf values have units.</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Rf value = A ratio used to identify substances Solvent = The medium that moves the analytes Chromatography = A technique to separate mixtures Retention factor = Another term for Rf value</p> Signup and view all the answers

    If a substance moves 4 cm and the solvent moves 8 cm, what is the Rf value?

    <p>0.5</p> Signup and view all the answers

    Calculating the Rf value does not require precise measurements.

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

    What is the first step in the paper chromatography method?

    <p>Use a ruler to draw a horizontal pencil line 2 cm from the end of the chromatography paper</p> Signup and view all the answers

    The unknown mixture of food colorings is labeled as T.

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

    What should be the maximum diameter of each spot applied to the chromatography paper?

    <p>2-3 mm</p> Signup and view all the answers

    The paper chromatography method is used to separate and identify a mixture of _____ colorings.

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

    How far from the end of the chromatography paper should the pencil line be drawn?

    <p>2 cm</p> Signup and view all the answers

    The spots for the known food colorings should be applied using the same capillary tube.

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

    After allowing the solvent to travel, what should you draw on the dry part of the paper?

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

    Study Notes

    Elements, Compounds & Mixtures

    • Substances can be classified as elements, compounds, or mixtures.
    • An element is a substance made of atoms with the same number of protons. These atoms cannot be broken down into simpler substances. There are 118 elements found on the Periodic Table. Examples include copper, iron, and magnesium.
    • A compound is a pure substance formed when two or more elements chemically combine. There are numerous compounds, and they cannot be separated into their constituent elements through physical methods. Examples include copper(II) sulfate (CuSO₄), calcium carbonate (CaCO₃), and carbon dioxide (CO₂).
    • A mixture is a combination of two or more substances (elements and/or compounds) that are not chemically combined. Mixtures can be separated by physical methods. Examples include sand and water, oil and water, and sulfur powder and iron filings.

    Pure Substance vs Mixture

    • A pure substance contains only one type of element or compound.
    • Pure substances have specific and sharp melting and boiling points.
    • Impure substances have a range of melting and boiling points, as they consist of more than one substance. Impure substances typically have lower melting points and higher boiling points than the pure substance.

    Separation Techniques: Simple Distillation

    • Used to separate a liquid from a solution containing a soluble solid or to separate two liquids with different boiling points.
    • The solution is heated, causing the liquid to evaporate and become a vapor.
    • The vapor then passes through a condenser, where it cools and condenses back into a liquid.
    • The pure liquid is collected in a beaker, leaving the dissolved solid behind.
    • An example is separating water from a salt-water solution.

    Separation Techniques: Fractional Distillation

    • Used to separate two or more miscible liquids with different boiling points.
    • The liquid with the lower boiling point evaporates first and is collected.
    • The column acts as a fractionating column, increasing surface area and allowing for slow condensation to occur.

    Separation Techniques: Filtration

    • Used to separate an undissolved solid from a liquid.
    • A filter paper is placed in a filter funnel above a beaker.
    • The mixture is poured into the filter funnel.
    • The liquid passes through the filter paper (filtrates), while the solid is retained on the filter paper (residue).

    Separation Techniques: Crystallisation

    • Used to separate a dissolved solid from a solution.
    • The solution is heated to evaporate the solvent.
    • The solution is cooled slowly, causing the dissolved solid to come out of solution as crystals.
    • The crystals are collected, washed, and dried.

    Paper Chromatography

    • Separates substances based on their different solubilities in a given solvent.
    • A pencil line is drawn on chromatography paper, and spots of the sample (like different colored inks) are placed on the line.
    • The paper is lowered into a solvent container, and the solvent travels up the paper by capillary action.
    • Substances with higher solubility travel further.
    • This separation allows the identification of the different components of a mixture.

    Interpreting Chromatograms

    • Chromatograms show the separation of substances in a mixture.
    • Pure substances produce a single spot on the chromatogram.
    • Mixtures produce multiple spots.
    • Substances can be identified based on their Rf values. Rf values are ratios obtained by dividing the distance traveled by the substance by the distance traveled by the solvent. They are useful because they are constant for a given substance in a given solvent system.

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    Edexcel IGCSE Chemistry Elements, Compounds & Mixtures PDF

    Description

    Test your understanding of the classifications of matter with this quiz on elements, compounds, and mixtures. Explore the differences between pure substances and mixtures while examining examples of each. Perfect for chemistry enthusiasts of all levels!

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