Cambridge IGCSE Chemistry - 0620 - Supplement Paper 4 2016 Winter Zone 2

Particles behave differently when in different physical states.
(a) Solids have a fixed volume and a definite shape.
Gases have no fixed volume and take the shape of the container.
Describe the volume and shape of liquids.
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(b) Complete the table to show the separation, arrangement and movement of particles in each physical state.
state | separation of particles | arrangement of particles | movement of particles
solid | .......................... | .......................... | ..........................
liquid | touching one another | randomly arranged | move over one another
gas | .......................... | .......................... | ..........................
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(c) Name the following changes of state.
(i) Ice turning into water.
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(ii) Solid carbon dioxide turning directly into gaseous carbon dioxide at room temperature.
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This question is about atoms, ions and isotopes.

(a) Define the term \textit{nucleon number}.
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(b) Give the electronic structure of the following atom and ion.

Na .........................................................................................................................
P^{3-} ................................................................................................................... [2]

(c) State one medical use of radioactive isotopes.

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(d) What is meant by the term \textit{relative atomic mass}?
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(e) Suggest why the relative atomic mass of chlorine is \textit{not} a whole number.
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(f) Aluminium is a metal in Group III.

Describe the bonding in aluminium.
Include a labelled diagram and any appropriate charges in your answer. [3]

Clean, dry air contains a small amount of carbon dioxide.
(a) The percentages of the other gases present in clean, dry air are shown in the table.
Complete the table by inserting the names of these gases.

[Table]
| name of gas | percentage present |
|-------------|-------------------|
| | 78 |
| | 21 |
| | 1 |
[2]

(b) Oxides of nitrogen are atmospheric pollutants which can cause acid rain.
Describe the formation of oxides of nitrogen and suggest how they can cause acid rain.
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(c) Methane contributes to the greenhouse effect.
State two sources of methane.
1 ............................................................................................................................
2 ............................................................................................................................ [2]

(d) Combustion and respiration add carbon dioxide to the atmosphere.
Name one natural process which removes carbon dioxide from the atmosphere.
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Dilute nitric acid behaves as a typical acid in some reactions but not in other reactions.

(a) Dilute nitric acid behaves as a typical acid when reacted with copper(II) oxide and with copper(II) carbonate.

Describe what you would see if excess dilute nitric acid is added separately to solid samples of copper(II) carbonate and copper(II) oxide followed by warming the mixtures.

copper(II) carbonate
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copper(II) oxide
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(b) When dilute nitric acid is added to pieces of copper and heated, a reaction takes place and copper(II) nitrate is formed.

(i) Part of the chemical equation for the reaction between copper and dilute nitric acid is shown.

Complete the chemical equation by inserting the formula of copper(II) nitrate and balancing the equation.
......Cu(s) + 8HNO$_3$(aq) $ ightarrow$ ...........................(aq) + 4H$_2$O(l) + 2NO(g) [2]

(ii) How is the reaction of dilute nitric acid with copper different from that of a typical acid?
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(a) Chlorine can be made in the laboratory by heating manganese(IV) oxide with concentrated hydrochloric acid.

$$\text{MnO}_2(s) + 4\text{HCl}(aq) \rightarrow \text{MnCl}_2(aq) + 2\text{H}_2\text{O}(l) + \text{Cl}_2(g)$$

Calculate the volume of 8.00 mol/dm³ HCl(aq) needed to react with 3.48 g of MnO₂.

• moles of MnO₂ used

..................................... mol

• moles of HCl needed

..................................... mol

• volume of HCl needed

..................................... cm³

(a) Describe how aluminium is extracted from bauxite. Include an ionic half-equation for the reaction at each electrode.
description .............................................................................................................................
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ionic half-equation for the anode reaction .............................................................................
ionic half-equation for the cathode reaction ...........................................................................[5]

(b) Explain why the anodes have to be replaced regularly.
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(c) Give two uses of aluminium and give a reason why aluminium is suitable for each use.
use 1 ...............................................................................................................................
reason ...............................................................................................................................
use 2 ...............................................................................................................................
reason ...............................................................................................................................[4]

Proteins are a major constituent of food.
Proteins are polymers.

(a) What is a polymer?
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(b) Proteins can be converted into amino acids.

(i) Name the type of chemical reaction which occurs when proteins are converted into amino acids.
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(ii) Suggest a condition needed to convert proteins into amino acids.
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(c) A colourless mixture of amino acids was separated by chromatography.
Amino acid $X$ has an $R_f$ value of 0.8.
The chromatogram of the mixture after treatment with a locating agent is shown.



(i) How is an $R_f$ value calculated?
$R_f =$ ............................................................................................................................................................. [1]

(ii) On the diagram put a ring around the spot caused by amino acid $X$. [1]

(iii) Describe how you would perform a chromatography experiment to produce the chromatogram shown in (c). Assume you have been given the mixture of amino acids and a suitable locating agent. You are provided with common laboratory apparatus.
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(d) When one molecule of an amino acid $A$ combines with one molecule of another amino acid $B$, two different dipeptide molecules could be formed.
Draw the structures of the two different dipeptide molecules.
Show all of the atoms and all of the bonds in the linkages.

[3]