1. 1
   A science technician demonstrates the reaction of a small piece of sodium with water in a shallow trough during a school chemistry lesson. The technician places the sodium onto the surface of the water using tongs. The sodium moves rapidly across the surface, fizzes vigorously, and eventually disappears completely. A gas is produced that gives a squeaky pop with a lit splint, and the resulting solution turns universal indicator purple.

   (a)

   Which of the following correctly classifies sodium according to its position in the periodic table?

   [1 mark]

   • ASodium is in group 1 and is classified as an alkali metal.
   • BSodium is in group 7 and is classified as a halogen.
   • CSodium is in group 0 and is classified as a noble gas.
   • DSodium is in group 2 and is classified as an alkaline earth metal.

   (b)

   Which statement about the physical properties of alkali metals such as sodium is correct?

   [1 mark]

   • AAlkali metals are hard and have very high melting points.
   • BAlkali metals are soft and have relatively low melting points.
   • CAlkali metals are brittle and do not conduct electricity.
   • DAlkali metals exist as gases at room temperature.

   (c)

   Describe two observations, other than the production of a gas, that the technician would make while the sodium reacts with the water.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A student sets up three separate trials to compare the reactivity of lithium, sodium and potassium with water. Small, equal-sized pieces of each metal are added to separate troughs of water containing a few drops of universal indicator, and the student times how long each piece takes to react fully and records how vigorous each reaction appears.

   (a)

   Which row correctly ranks lithium, sodium and potassium from least reactive to most reactive with water?

   [1 mark]

   • Apotassium, lithium, sodium
   • Bpotassium, sodium, lithium
   • Csodium, lithium, potassium
   • Dlithium, sodium, potassium

   (b)

   Which statement describes how the number of electron shells changes going down group 1 from lithium to potassium?

   [1 mark]

   • AThe number of electron shells decreases.
   • BThe number of electron shells stays the same.
   • CThe number of electron shells increases.
   • DThe number of electron shells doubles and then decreases.

   (c)

   Use the student's results to predict how rubidium, the next element in group 1 after potassium, would react with water compared with potassium.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A teacher shows a video recording of potassium reacting with water in a fume cupboard. In the recording, the potassium moves rapidly across the surface of the water and ignites, burning with a lilac flame, before disappearing completely. The teacher then asks the class to use the electronic configurations of lithium (2.1), sodium (2.8.1) and potassium (2.8.8.1) to explain the pattern in reactivity that has been observed.

   (a)

   Describe the reaction of potassium with water, based on the recording, including reference to observations that show this reaction is more vigorous than the reaction of sodium with water.

   [3 marks]

   (b)

   Using the electronic configurations given, lithium (2.1), sodium (2.8.1) and potassium (2.8.8.1), explain why reactivity with water increases going down group 1 from lithium to potassium.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A company that manufactures laboratory storage equipment is designing safety guidance for storing samples of lithium, sodium and potassium in school and industrial laboratories. The company asks a chemistry consultant to prepare a briefing document explaining the properties of the alkali metals and the precautions that should be taken when storing and handling them.

   (a)

   Using ideas about electronic configuration, explain the pattern in reactivity of lithium, sodium and potassium with water, and use this pattern to predict how caesium, which lies below potassium in group 1, would react with water.

   [6 marks]

   (b)

   Evaluate why samples of lithium, sodium and potassium must be stored under oil and handled with tongs rather than with bare hands, referring to their physical properties and their reactions with water and oxygen.

   [6 marks]

   Total for question 4: 12 marks

End of questions