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Year 11
OCR
Higher

Reactions of the halogens: including displacement practical

I can write word and symbol equations to show how Group 7 elements react.

Download all resources
Share activities with pupils
New
New
Year 11
OCR
Higher

Reactions of the halogens: including displacement practical

I can write word and symbol equations to show how Group 7 elements react.

Download all resources
Share activities with pupils

Lesson details

Key learning points

  1. Halogens can be dissolved in water to form acidic solutions.
  2. A more reactive halogen can displace a less reactive one from a compound.
  3. Group 7 elements react with Group 1 and 2 metals to form salts.
  4. The chemical test for chlorine involves passing the gas over damp blue litmus paper.

Common misconception

Halogen solutions are coloured and sometimes it can be difficult to determine colour changes during displacement reactions.

Displacement of iodine gives the darkest colour change (turns brown), while bromine will provide one which is lighter (turns orange).

Keywords

  • Displacement - reaction is where a more reactive element replaces a less reactive element in a compound.

  • Solution - is formed when a substance dissolves in a liquid.

  • Halides - are the name of salts formed from halogens, e.g. sodium chloride (NaCl).

Demonstrate the colour changes before the pupils embark on the experiment to ensure they know what colour changes to expect.
Teacher tip

Equipment

Chlorine, bromine and iodine solutions, chloride, bromide and iodide solutions (Group 1 halides work well), spotting tiles and pasteur pipettes.

Content guidance

  • Risk assessment required - equipment

Supervision

Adult supervision required

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Video

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Starter quiz

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6 Questions

Q1.
Match the keyword to the correct statement.
Correct Answer:salts,Ionic compounds formed from positive and negative ions.

Ionic compounds formed from positive and negative ions.

Correct Answer:halide,A salt formed from a halogen.

A salt formed from a halogen.

Correct Answer:diatomic elements,Two atoms of the same type chemically bonded together.

Two atoms of the same type chemically bonded together.

Correct Answer:Group 7,Non metallic elements which react with metals to form halide salts.

Non metallic elements which react with metals to form halide salts.

Q2.
Which trends occur in Group 7 elements going down the group?
melting points decrease
Correct answer: melting points increase
Correct answer: boiling points increase
boiling points decrease
size of atoms and molecules decrease
Q3.
What happens to the forces of attraction between atoms going down Group 7?
Correct answer: they become stronger
they become weaker
they stay the same
Q4.
Going down Group 7, the molecules become more packed together and density increases.
Correct Answer: tightly, closely, densely
Q5.
Place the halogens in order of their density at room temperature. Place the least dense halogen first.
1 - fluorine
2 - chlorine
3 - bromine
4 - iodine
5 - astatine
Q6.
Which statement explains why reactivity decreases down Group 7?
Correct answer: It becomes more difficult to gain an electron as the size of the atom increases.
It becomes easier to gain an electron as the size of the atom increases.
The distance of the outer electron from the nucleus decreases.
Correct answer: The distance of the outer electron from the nucleus increases.

Exit quiz

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6 Questions

Q1.
Which of these halogens is the least reactive?
fluorine
bromine
Correct answer: iodine
chlorine
Q2.
What products are formed when chlorine gas is bubbled through a solution of lithium bromide?
bromine and lithium
Correct answer: lithium chloride and bromine
chlorine and lithium bromide
no reaction takes place
Q3.
Choose the chemical test which would indicate chlorine gas was present.
Turns damp red litmus paper blue.
Produces a squeaky pop sound when a lit splint is exposed to the gas.
Damp blue litmus paper stays blue.
Correct answer: Turns damp blue litmus paper red, then bleaches white.
Q4.
What happens when halogen atoms react to form halide salts?
Correct answer: They gain an outer electron.
They lose an outer electron.
Correct answer: They become stable negative ions.
They become stable positive ions.
Q5.
What happens when a halogen and a Group 1 metal react?
Correct answer: A Group 1 atom transfers an outer electron to a Group 7 atom.
A Group 7 atom transfers an outer electron to a Group 1 atom.
Correct answer: Oppositely charged ions are formed which electrostatically attract each other.
Identically charged ions are formed which electrostatically attract each other.
Q6.
Choose the correct word equation to show the displacement reaction between bromine and potassium chloride.
Correct answer: bromine + potassium chloride → bromine + potassium chloride
bromine + potassium chloride → bromide + potassium chlorine
bromine + potassium chloride → chlorine + potassium bromide
bromine + potassium chloride → potassium + bromine chloride