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States of matter

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Question 4

A teacher demonstrates, in a fume cupboard, two experiments to show the movement of particles.

a.

In the first experiment she places some brown nitrogen dioxide gas at the bottom of a gas jar. She then places another gas jar containing colorless oxygen gas on top of it, as shown in the diagram.

The diagram shows the apparatus at the start, after a few minutes and at the end of the experiment.

Three vertically stacked pairs of gas jars. In the 'start' pair, the bottom jar contains a dense brown gas labeled 'nitrogen dioxide' and the top jar contains a colorless gas labeled 'oxygen'. In the 'after a few minutes' pair, the brown gas has begun spreading upwards, showing a gradual transition from dark brown at the bottom to light brown in the middle of the upper jar. In the 'end' pair, both jars are completely filled with a uniform light brown color.

Choose two statements that are correct about this experiment:

  • A All the oxygen particles in the upper gas jar stay there.
  • B Nitrogen dioxide and oxygen react to form a liquid.
  • C Nitrogen dioxide has a darker color than oxygen.
  • D Nitrogen dioxide gas diffuses upwards.
  • E Nitrogen dioxide gas condenses to a solid during the experiment.
  • F The concentration of nitrogen dioxide in the lower gas jar does not change.
[2]
b.

In the second experiment, she soaks two pieces of cotton wool in different liquids and places them at opposite ends of a glass tube. She immediately seals the tube with bungs.

The diagram shows the apparatus at the start of the experiment.

A long horizontal glass tube sealed with rubber bungs at both ends. On the left inside of the tube, there is cotton wool soaked in ammonia solution. On the right inside of the tube, there is cotton wool soaked in concentrated hydrobromic acid. Below the tube, three points are labeled: 'X' is near the left-middle section, 'Y' is at the center, and 'Z' is near the right-middle section close to the hydrobromic acid.

During the experiment a white ring of ammonium bromide appears in the tube.

State whether the white ring appears at X, Y or Z.

[1]
c.

Explain your choice.

[3]

States of matter Questions

  1. IGCSE
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  3. /States of matter