O LevelChemistryCambridge (CIE)Exam Questions6. Chemical Reactions6.1 Physical & Chemical Changes

Physical & Chemical Changes (Cambridge (CIE) O Level Chemistry): Exam Questions

Exam code: 5070

2 hours30 questions

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6.1 Physical & Chemical Changes

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1
1 mark

Which of the following processes represents a physical change?

  • Acid-base neutralisation

  • Metal displacement reactions

  • Boiling ethanol

  • Combustion of magnesium

Choose your answer

2
1 mark

Physical and chemical changes are different processes. Which of the following rows correctly identifies characteristics of each one?

 

chemical change

physical change

A

no new substance formed

change of state

B

no new substance formed

involves electron transfer

C

new substance formed

involves electron transfer

D

new substance formed

change of state

    Choose your answer

    3
    1 mark

    Which observation is evidence that a chemical change has taken place?

    • A green solid turns black and gives off a gas that turns limewater milky.

    • A grey solid turns to a purple vapour when it is warmed.

    • A white solid disappears when it is stirred into water.

    • A blue solution becomes paler when more water is added to it.

    Choose your answer

    4
    1 mark

    Three statements about chemical changes are shown.

    1 One or more new substances are formed.

    2 The change is always easy to reverse.

    3 The total mass of the products equals the total mass of the reactants.

    Which statements are correct?

    • 1, 2 and 3

    • 1 and 2 only

    • 1 and 3 only

    • 2 and 3 only

    Choose your answer

    5
    1 mark

    Which pair of changes are both physical changes?

    • melting candle wax and dissolving sugar in water

    • burning candle wax and dissolving sugar in water

    • melting candle wax and rusting iron

    • heating limestone and freezing water

    Choose your answer

    1
    1 mark

    Solid carbon dioxide is left in a warm room. It turns directly into carbon dioxide gas without forming a liquid.

    Which row gives the type of change and the correct reason for it?

    type of change

    reason

    A

    chemical

    a gas is produced

    B

    chemical

    the covalent bonds inside the carbon dioxide molecules break

    C

    physical

    the carbon dioxide molecules move much further apart

    D

    physical

    the covalent bonds inside the carbon dioxide molecules break

      Choose your answer

      2
      1 mark

      Solid calcium chloride is stirred into water. All of the solid dissolves and the temperature of the water rises from 19 °C to 27 °C.

      Which row gives the type of change and the correct reason for it?

      type of change

      reason

      A

      chemical

      the temperature of the water rises

      B

      chemical

      the calcium chloride is no longer visible

      C

      physical

      no energy is transferred between the calcium chloride and the water

      D

      physical

      the calcium chloride can be recovered unchanged by evaporating the water

        Choose your answer

        3
        1 mark

        A student carries out two changes.

        change 1: solid wax is melted

        change 2: magnesium is burned in air

        Which row correctly describes what happens to the particles in each change?

        change 1

        change 2

        A

        the particles are rearranged into new substances

        the particles are rearranged into new substances

        B

        the particles are rearranged into new substances

        the same particles are arranged differently

        C

        the same particles are arranged differently

        the particles are rearranged into new substances

        D

        the same particles are arranged differently

        the same particles are arranged differently

          Choose your answer

          4
          1 mark

          In each of these four processes a change is made and then reversed, so that the original substance is obtained again.

          In which process does no reaction take place at either stage?

          • Water is frozen to ice, then the ice is melted.

          • Blue hydrated copper(II) sulfate is heated to a white solid, then water is added to the white solid.

          • Pink cobalt(II) chloride is warmed until it turns blue, then damp air is passed over it.

          • Calcium oxide is added to water, then the product is heated strongly.

          Choose your answer

          5
          1 mark

          Which process is a physical change?

          • cracking of an alkane

          • hydration of ethene

          • fractional distillation of petroleum

          • thermal decomposition of calcium carbonate

          Choose your answer

          1
          1 mark

          Silicon(IV) oxide has a giant covalent structure. It melts at 1710 °C.

          Which row gives the type of change when silicon(IV) oxide melts, and the correct reason for it?

          type of change

          reason

          A

          chemical

          Si–O covalent bonds break

          B

          chemical

          a substance with a different structure is formed

          C

          physical

          no new substance is formed, even though Si–O covalent bonds break

          D

          physical

          only the forces between separate silicon(IV) oxide molecules are overcome

            Choose your answer

            2
            1 mark

            Blue hydrated copper(II) sulfate crystals are heated. Steam is given off and a white solid is left behind.

            When water is added to the white solid it turns blue again.

            Which row gives the type of change when the crystals are heated, and the correct reason for it?

            type of change

            reason

            A

            physical

            the change can be reversed by adding water

            B

            physical

            water is only driven out from between the crystals

            C

            chemical

            the copper(II) sulfate is broken down into its elements

            D

            chemical

            a substance with a different formula is formed

              Choose your answer

              3
              1 mark

              A chemical change takes place inside a sealed container.

              1 the total mass of the substances in the container

              2 the total number of atoms in the container

              3 the total number of molecules in the container

              Which quantities are always unchanged by a chemical change in a sealed container?

              • 1, 2 and 3

              • 1 and 2 only

              • 1 and 3 only

              • 2 and 3 only

              Choose your answer

              4
              1 mark

              Each of these four changes produces a gas.

              In which change is no new substance formed?

              • Liquid air is warmed and nitrogen boils off.

              • Zinc is added to dilute hydrochloric acid.

              • Solid sodium hydrogencarbonate is heated.

              • Aqueous hydrogen peroxide is mixed with manganese(IV) oxide.

              Choose your answer

              5
              1 mark

              In each of these four experiments a white solid appears in a colourless solution.

              In which experiment is the change physical?

              • A hot saturated solution of potassium nitrate is cooled.

              • Aqueous barium nitrate is added to aqueous sodium sulfate.

              • Carbon dioxide is bubbled through limewater.

              • Aqueous silver nitrate is added to aqueous sodium chloride.

              Choose your answer