901
89
Describe characteristic properties and reactions of related substances.
Credits: Five
You should answer ALL the questions in this booklet.
A Table of Ions and Periodic Table are provided in the RESOURCE BOOKLET 90189R.
For Assessor’s use only
Achievement Criteria
Achievement Achievement with Merit
Explain characteristic properties and reactions of related substances.
Overall Level of Performance
Achievement with Excellence
Apply an understanding of characteristic properties and reactions of related substances.

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© New Zealand Qualifications Authority, 2003
All rights reserved. No part of this publication may be reproduced by any means without the prior permission of the New Zealand Qualifications Authority.
You are advised to spend 40 minutes answering the questions in this booklet.
QUESTION ONE: METALS
Magnesium is often used in school laboratories because it is a reactive metal.
(a) Name TWO metals that are more reactive than magnesium.
(1) sodium
(2) potassium
(b) Magnesium metal burns well in air. air.
(i) Describe TWO things that you would observe when a piece of magnesium is burned in
(1) bright white light

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(2) White powder left over
(ii) Write a word equation for the reaction in (b) (i)
(c) Some students are making jewellery in their technology classes. They need to choose a suitable metal to make a bracelet. One student, Terri, decides to use magnesium because it is very light. Another, Sione, says he thinks that copper would be much better because it is a good conductor of heat.
Discuss the suitability of each metal for making a bracelet. Refer to the ideas of Terri and
Sione and use other properties of magnesium and copper in your answer.
Magnesium is light but is also very reactive not as strong
Copper is good conducter stronger less reactive more commonly found

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QUESTION TWO: ACIDS AND ALKALIS
Increased concentrations of acid in the stomach can cause indigestion.
(a) Describe what will happen to the pH value of the stomach contents when the concentration of acid in the stomach is increased.
‘AntiAcid’ is an antacid in tablet form for treating indigestion. The antacid treatment can neutralise the acid.
The antacid treatment tablet contains the two metal compounds, magnesium hydroxide and calcium carbonate.
(b) What would you observe when calcium carbonate and acid react together?
Bubbling fizzing gas giving off
(c) Write the formula for magnesium hydroxide. You can use the ion table inside the Resource
Booklet to help you.
MgOH
(d) What colour would litmus solution turn when drops of it are put onto some magnesium hydroxide? Give a reason for your answer.
Colour : blue
Reason: all hydroxides are bases
(e) Discuss why the reaction between magnesium hydroxide and stomach acid (hydrochloric acid, HCl) can be called a neutralisation reaction. You may use equations in your answer.

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QUESTION THREE: FUELS
(a) Burning alkanes in a Bunsen burner with a yellow flame can result in steam (water) and up to three other products.
(i) Name a product that would be black.
Carbon powder
(ii) Name a product that would be poisonous. Carbon monoxide
(iii) Name a product that would turn limewater milky. Carbon dioxide
(b) Discuss how the Bunsen burner flame can be altered to give each of the three products in (a) above, and why these substances are produced. Complete combustion = carbon dioxide
Incomplete combustion = carbon monoxide and carbon powder
(c) Write a balanced chemical equation for the complete combustion of the alkane propane.

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(d) Methane is another alkane. There are many ways to show the methane molecule; two ways are shown below.
Sources: www.biologylessons.sdsu.edu/ta/classes/lab3/methane.gif
Chemistry for Today, 3rd edn, Seager and Slabaugh, Brooks/Cole (USA) 1997.
Draw the structural formula of methane.
(e) Many fuels are hydrocarbons.
(i) Name the TWO elements that are present in all hydr ocarbons.
(ii) At room temperature, methane is a hydrocarbon that is a gas, and hexane is a liquid hydrocarbon.
Discuss why methane is a gas, but hexane is a liquid at room temperature.