Group 1: the alkali metalsIB MYP Chemistry: Subtopic test

1. 1
   A school technician in Singapore is preparing a demonstration for a Year 9 class. A small piece of sodium is taken from a bottle of oil, cut with a knife, dried and dropped into a large trough of water containing a few drops of universal indicator. The class will watch from behind a safety screen.

   (a)

   Why is sodium stored under oil?

   [1 mark]

   • ATo stop it melting
   • BTo stop it reacting with oxygen and water vapour in the air
   • CTo make it sink in water
   • DTo make it easier to cut

   (b)

   What colour does the universal indicator turn after the reaction?

   [1 mark]

   • ARed
   • BYellow
   • CGreen
   • DPurple

   (c)

   Write the word equation for the reaction of sodium with water.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A teacher drops equal-sized small pieces of lithium, sodium and potassium into three separate troughs of water. Lithium floats and fizzes steadily until it disappears. Sodium floats, melts into a silvery ball and fizzes rapidly, darting across the surface. Potassium floats, melts, darts about very quickly and burns with a lilac flame.

   (a)

   Which statement describes the pattern in the results?

   [1 mark]

   • AReactivity with water increases from lithium to potassium
   • BReactivity with water decreases from lithium to potassium
   • CAll three metals have the same reactivity with water
   • DSodium is the most reactive of the three metals

   (b)

   Rubidium is the Group 1 metal below potassium. What is the best prediction of its reaction with water?

   [1 mark]

   • AIt fizzes more slowly than potassium
   • BIt fizzes at the same rate as lithium
   • CIt reacts even more vigorously than potassium
   • DIt does not react with water

   (c)

   Explain, in terms of electrons, why potassium is more reactive than sodium.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student wants to compare the reactivity of lithium, sodium and potassium. She plans to add a small piece of each metal, one at a time, to a large beaker of water at room temperature and to time how long each piece takes to stop fizzing. Her teacher will cut and dry each piece for her.

   (a)

   State a testable hypothesis for her investigation, with a scientific reason, and identify the independent variable.

   [3 marks]

   (b)

   Outline a safe method she could use. Name the dependent variable and two variables she should control.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A teacher repeats the water experiment and records the time that each 0.1 g piece takes to react completely in the same volume of water at 20 °C: lithium 150 s, sodium 40 s, potassium 8 s. A school in the next district has banned students from handling Group 1 metals and only allows teacher demonstrations, because the metals must be stored under oil and the reactions can be dangerous.

   (a)

   Describe the trend in the results and explain it using electronic structure.

   [6 marks]

   (b)

   Discuss and evaluate whether students should be allowed to carry out Group 1 metal reactions themselves.

   [6 marks]

   Total for question 4: 12 marks

End of questions