Solids, Liquids & Gases (CIE IGCSE Chemistry: Co-ordinated Sciences (Double Award))

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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.

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:

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

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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.

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

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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?

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

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Name the change of state which occurs in region DE.

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

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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.

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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.

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.

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

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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.

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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.

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Diagram 3

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Ethylamine reacts with acids to form salts.

CH₃CH₂NH₂      +     HCl    →   CH₃CH₂NH₃Cl

                                                                ethylammonium chloride

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

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Different gases diffuse at different speeds.

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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.

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.

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Z is a covalent substance. In an experiment, a sample of pure solid Z was continually heated for 11 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?

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The sample of pure Z began to boil at 9 minutes. It was boiled for 2 minutes.
 
Use this information to sketch on the grid, in part (a), how the temperature of the sample of pure Z changed between 9 minutes and 11 minutes.

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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.

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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:

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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.

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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.

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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.

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

The following results were obtained.

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