### Describe and explain trends in physical properties

Interpret reactions of halogens with hydrogen

Outline displacement reactions of halogens and halide ions

Work through the tasks listed below - each one should take no more than 10 minutes, be strict with your timings! Before you start open, the exam style questions by clicking the button below, AFTER each task attempt the questions associated with what you have just covered and check your answer with your teacher before moving on!

Below if a document that has some support questions and prompts if you get really stuck on any task. Check these first and then ask your teacher for help - do not just google the answers!

# Physical properties

**Task 1:** For the following properties describe and sketch the graph of the trend as you descend the group (F to I only):

Atomic radius

Electronegativity

Melting point

Bond enthalpy of X-X (use the data booklet)

Check your graphs with those on the link below and then attempt the **Task 1 MCQ**

**Task 2**: Use your knowledge to EXPLAIN the trends for each of the properties described above. Think about your understanding of structure and bonding to aid your explanations, especially with the bond enthalpy of fluorine!

If you find yourself getting really stuck read the supporting questions and prompts before answering in your own words.

Complete **Task 2 MCQ**.

# Reactivity

**Task 3**: Sketch a graph of the bond enthalpies for the hydrogen halides - HX. Use the data booklet for the values. Compare this to the bond enthalpies of the elemental halogens from task 1.

Using your knowledge explain the difference in trends. Again, use the support questions & prompts if you require some guidance.

**Task 4:** Write the balanced equations for the reactions between hydrogen and each halogen from fluorine to iodine. Once you have done that calculate the enthalpy change for each reaction (using data from the data booklet).

If you feel you need help doing this check out the sample calculation below then try the others. If you are still not sure ask your teacher for help!

Check your enthalpy calculations with your teacher!

Now complete the **Task 3 & 4 Exam question** - relate your answers to the bond enthalpies you have just calculated

Now let's think about if we did these experiments, what would we observe?

**Casalis' Crazy Challenge:** - using the enthalpy change values try and **predict** what you may **OBSERVE** when the reactions happen and think about the **CONDITIONS** (some may have a high activation energy).

**For less of a challenge:** on the document below there are a list of choices for **observations & conditions** - try and match them to each reaction.

Once you have done this watch the videos below to check your answers!

You might notice there is no iodine + hydrogen video - this is because an equilibrium is set up and not much exciting really happens...

**Casalis' Crazy Challenge (homework) **- give details of an experiment to show the bond enthalpy of the C-X bond of different halogens, including details of how you would **break** the bond and **prove** the bond has been broken.

# Displacement reactions

Experiment time!

On the link below there is a method for a series of short practicals to find out the COLOUR of the halogens and how they react with halide ions.

Record your results in a table (there is a sample one if necessary) and write a conclusion outlining what your results tell you. There are some prompt questions in the method if you feel you need guidance (scroll down once you have written your conclusion to check you have covered all the main points)

Further work / homework

Go through all your work done this lesson. Make sure you have completed all the tasks, a few days later read your work back - is there anything you are not completely sure with? If so go to chemguide and remember you can ask questions on Google Classroom/email/bring them to class!