Solids, liquids & gases (Cambridge (CIE) IGCSE Chemistry)

Extended Only

Concentrated ammonia solution gives off ammonia gas. Concentrated hydrochloric acid gives off hydrogen chloride gas. Ammonia, NH₃, and hydrogen chloride, HCl, are both colourless gases. Ammonia reacts with hydrogen chloride to make the white solid ammonium chloride.

Apparatus is set up as shown.

After ten minutes a white solid forms in the tube where the gases meet.

i) Write the chemical equation for the reaction of ammonia with hydrogen chloride.

[1]

ii) Name the process by which the ammonia and hydrogen chloride gases move in the tube.

[1]

iii) At which point, A, B, C or D, does the white solid form? Explain why the white solid forms at that point.

[3]

iv) The experiment was repeated at a higher temperature. Predict how the results of the experiment would be different. Explain your answer.

[3]

Some of the white solid is removed from the tube and dissolved in water.

Describe how the white solid could be tested to show it contains:

i) Ammonium ions.

Test ...........................

Result .......................

[3]

ii) Chloride ions.

Test .........................

Result .....................

[3]

Extended Only

The diagram shows the electron arrangement in a molecule of ammonia, showing only outer shell electrons.

i) State the type of bonding in ammonia.

[1]

ii) Hydrazine, N₂H₄, is another compound of nitrogen and hydrogen. Complete the diagram to show the electron arrangement in a molecule of hydrazine, showing only outer shell electrons.

[3]

Separate: Chemistry and Extended Only

Nylon and proteins are both polymers containing nitrogen.

i) Name the linkages found in the polymers of nylon and protein.

[1]

ii) Describe one difference in the structures of nylon and protein.

[1]

iii) What is the general name given to the products of hydrolysis of proteins?

[1]

Extended Only

Suggest the structure of the monomer used to make the polymer shown.

Extended Only

Compound X is a colourless liquid at room temperature.

A sample of pure X was slowly heated from –5.0 °C, which is below its melting point, to 90 °C, which is above its boiling point. Its temperature is measured every minute and the results are represented on the graph.

i) Complete the equation for the equilibrium present in the region BC.

X (s) ....................

[1]

ii) What is the significance of temperature t °C?

[1]

iii) What is the physical state of compound X in the region EF?

[1]

iv) What would be the difference in the region BC if an impure sample of X had been used?

[1]

Separate: Chemistry and Extended Only

Compound X is a hydrocarbon. It contains 85.7% of carbon. The mass of one mole of X is 84 g.

i) What is the percentage of hydrogen in the compound ?

[1]

ii) Calculate the empirical formula of X. Show your working.

[3]

iii) What is the molecular formula of compound X?

[1]

Extended Only

The diagram shows a heating curve for a sample of compound X.

Is X a solid, a liquid or a gas at room temperature, 20 °C?

Extended Only

Write an equation for the equilibrium which exists in region BC.

Extended Only

Name the change of state which occurs in region DE.

Extended Only

Explain how the curve shows that a pure sample of compound X was used.

Extended Only

Ethanoic acid is a colourless liquid at room temperature. It has the typical acid properties and forms compounds called ethanoates.

A pure sample of ethanoic acid is slowly heated from 0 ^oC to 150 ^oC and its temperature is measured every minute. The results are represented on the graph below.

i) Name the change that occurs in the region D to E.

[1]

ii) What would be the difference in the region B to C if an impure sample had been used?

[1]

iii) Sketch on the graph how the line would continue if the acid was heated to a higher temperature.

[1]

iv) Complete the following table that compares the separation and movement of the molecules in regions C to D with those in E to F.

[5]

Complete the word equations for the reactions of ethanoic acid.

calcium + ethanoic acid → ................................................ +  .........................................

................................................  +  ethanoic acid   →  zinc ethanoate + water

Write the symbol equation for the reaction between ethanoic acid and sodium hydroxide.

Element X can undergo the following physical changes.

Figure 1.1

Name each of the numbered physical changes shown in Figure 1.

One difference between boiling and evaporation is the rate at which the processes occur.

State one other difference between boiling and evaporation.

Element X can undergo the following physical changes.

Figure 1.1

Describe the separation, arrangement and motion of particles of element X in the solid state.

 Separation: ..................................................

 Arrangement: ..................................................

 Motion: ..................................................

This question is about iodine and compounds of iodine.

Use the kinetic particle model to describe the separation between the molecules and the type of motion of the molecules in:

Solid iodine:

Iodine gas:

The graph shows how the volume of iodine gas changes with pressure. The temperature is kept constant.

Describe how the volume of iodine gas changes with pressure.

Sulfur dioxide melts at –73 °C and boils at –10 °C.

What is the physical state of sulfur dioxide at –20 °C?

Explain your answer.

Nitrogen dioxide, NO₂, is a dark brown gas.

When nitrogen dioxide is cooled, it forms a yellow liquid and then pale yellow crystals.

These crystals are heated and the temperature is measured every minute. The following graph can be drawn.

i) Describe the arrangement and movement of the molecules in the region A–B.

[3]

ii) Name the change that occurs in the region B–C.

[1]

Extended Only

Nitrogen dioxide and other oxides of nitrogen are formed in car engines.

i) Explain how these oxides are formed.

[2]

ii) How are they removed from the exhaust gases?

[2]

Extended Only

Nitrogen dioxide, oxygen and water react to form dilute nitric acid.

Describe how lead(II) nitrate crystals could be prepared from dilute nitric acid and lead(II) oxide.

A small amount of liquid bromine is added to a container which is then sealed.

Br₂(l) → Br₂(g)

Use the ideas of the Kinetic Theory to explain why, after about an hour, the bromine molecules have spread uniformly to occupy the whole container.

Extended Only

The diagrams below show simple experiments on the speed of diffusion of gases.

Complete the following explanations. Diagram 1 has been done for you.

Diagram 1 There is air inside and outside the porous pot so the rate of diffusion of air into the pot is the same as the rate of diffusion of air out of the pot. The pressure inside and outside the pot is the same so the coloured liquid is at the same level on each side of the tube.

Diagram 2.

................................

Diagram 3

................................

Separate: Chemistry and Extended Only

Acid-base reactions are examples of proton transfer.

Ethylamine is a weak base and sodium hydroxide is a strong base.

i) In terms of proton transfer, explain what is meant by the term weak base.

[2]

ii) Given aqueous solutions of both bases, describe how you could show that sodium hydroxide is the stronger base. How could you ensure a ‘fair’ comparison between the two solutions?

[3]

Ethylamine reacts with acids to form salts.

CH₃CH₂NH₂      +     HCl    →   CH₃CH₂NH₃Cl

                                                                ethylammonium chloride

i) Complete the equation for the reaction between sulfuric acid and ethylamine. Name the salt formed.

......  CH₃CH₂NH₂       +       ............     →     .........................

Name of salt ........................................................................

[3]

ii) Amines and their salts have similar chemical properties to ammonia and ammonium salts.

Suggest a reagent that could be used to displace the weak base, ethylamine, from its salt ethylammonium chloride.

[1]

Extended Only

Gases diffuse, which means that they move to occupy the total available volume.

i) Explain, using kinetic particle theory, why gases diffuse.

[2]

ii) When the colourless gases hydrogen bromide and ethylamine come into contact, a white solid is formed.

CH₃CH₂NH₂ (g) + HBr (g)     →     CH₃CH₂NH₃Br (s)

      white solid

The following apparatus can be used to compare the rates of diffusion of the two gases ethylamine and hydrogen bromide.

Predict at which position, A, B or C, the white solid will form. Explain your choice.

[3]

Extended Only

Different gases diffuse at different speeds.

i) What is meant by the term diffusion?

[1]

ii) What property of a gas molecule affects the speed at which it diffuses?

[1]

Extended Only

Helium is a gas used to fill balloons. It is present in the air in very small quantities. Diffusion can be used to separate it from the air. Air at 1000°C is on one side of a porous barrier. The air which passes through the barrier has a larger amount of helium in it.

i) Why does the air on the other side of the barrier contain more helium?

[1]

ii) Why is it an advantage to have the air at a high temperature?

[1]

Most helium is obtained from natural gas found in the USA. Natural gas contains methane and 7% helium. One possible way to obtain the helium would be to burn the methane.

i) Write an equation for the complete combustion of methane.

[1]

ii) Suggest why this would not be a suitable method to obtain the helium.

[1]

iii) Suggest another method, other than diffusion, by which helium could be separated from the mixture of gases in natural gas.

[1]

Extended Only

Z is a covalent substance. In an experiment, a sample of pure solid Z was continually heated for 12 minutes.

The graph shows how the temperature of the sample of pure Z changed during the first 9 minutes.

What is the melting point of pure Z?

Extended Only

The sample of pure Z began to boil at 9 minutes. It was boiled for 3 minutes.   Use this information to sketch on the grid, in part (a), how the temperature of the sample of pure Z changed after 9 minutes.

Extended Only

The sample of pure Z was continually heated between 2 minutes and 5 minutes.  

Explain, in terms of attractive forces, why there was no increase in the temperature of the sample of pure Z between 2 minutes and 5 minutes.

Extended Only

Describe how the motion of particles of pure Z changed from 0 minutes to 2 minutes.

The experiment was repeated using a solid sample of impure Z.

Suggest the differences, if any, in the melting point and boiling point of the sample of impure Z compared to the sample of pure Z.

melting point:

boiling point:

Extended Only

A sample of pure Z was allowed to cool from 120 °C to 20 °C. The total time taken was 8 minutes.

 Starting from point ×, sketch on the grid how the temperature of the sample of pure Z changed between 0 minutes and 8 minutes.

Extended Only

Kinetic theory explains the properties of matter in terms of the arrangement and movement of particles.

Nitrogen is a gas at room temperature. Nitrogen molecules, N₂, are spread far apart and move in a random manner at high speed.

i) Draw the electronic structure of a nitrogen molecule. Show only the outer electron shells.

[2]

ii) Compare the movement and arrangement of the molecules in solid nitrogen to those in nitrogen gas.

[3]

Extended Only

A sealed container contains nitrogen gas. The pressure of the gas is due to the molecules of the gas hitting the walls of the container.

Use the kinetic theory to explain why the pressure inside the container increases when the temperature is increased.

Extended Only

The following apparatus can be used to measure the rate of diffusion of a gas.

The following results were obtained.

i) Explain why nitrogen gas diffuses faster than chlorine gas.

[2]

ii) Explain why the nitrogen gas diffuses faster at the higher temperature.

[1]