Chemistry

Metals: What makes them unique?

We have known for centuries that metals are an important material that can be used in many different ways. More recent applications in “nanomedicine” have created a whole new avenue of scientific discovery.

In this lesson you will investigate the following:

• What is metallic bonding?

• How can metallic bonding be used to predict the properties of a metal?

• What is nanotechnology?

• What are some of the applications of metals in nanotechnology?

So put on your suit of armour and charge through this lesson!

This is a print version of an interactive online lesson. To sign up for the real thing or for curriculum details about the lesson go to www.cosmosforschools.com

Introduction: Metals (P1)

Metals have played a vital role in the development of the human species from nomadic hunters to settled builders. Weeven use them to describe stages of our development on that journey. The Iron Age and the Bronze Age, for example, give a quickpicture of the technology humans used at the time.

But we still haven’t finished finding new ways to use metals and their amazing properties.

The very latest uses are in medicine. Scientists have just discovered a way we can use palladium – a rare silver-coloured metal – as away to better deliver cancer drugs to patients.

The problem with cancer drugs is that, while they kill the cancer cells, they can also poison healthy cells. So if we can find a way toplace the drug in only the cancer cells, there is less chance the patient’s healthy cells will be affected. And it looks like scientists havefound a way to do just that.

The technique is to put a very, very tiny piece of palladium in the patient’s tumour. Then the cancer drug is wrapped up in achemical that prevents it from activating after the patient has taken it. When the drug encounters the palladium, the metal acts as acatalyst to remove the chemical sheath, releasing the cancer drug at exactly the right place so it will kill cancer cells but not hurthealthy cells.

It’s too early to start calling this “the Palladium Age” but it shows how important metals are to us and in ways we are only justdiscovering.

Read or listen to the full Cosmos magazine article here.

Left: Palladium is a rare, dense metal, whose name originates from Pallas, daughter of Triton, of Greek mythology. Right:Palladium may help make cancer patients treatments less painful. Credit: SPL / Getty Images & 123RF.

Question 1

Imagine: You are a scientist involved in the experimental stages of a new cancer drug. You are aware that the metal palladium is anactive agent during stages of the treatment. What issues do you think this might raise and how might you address these issues?

Gather: Metals (P1)

Credits: 123RF and iStock

Question 1

Identify: There are numerous ways that metals can be used. Use the images above to identify as many as possible.

The macroscopic scale covers items that are clearly visible to the eye. The items above are examples of this and their uses andphysical properties can be easily identified.

Question 2

Research: Using the images above as a starting point, match the use of a metal to its most important physical property. Provide abrief description of each in the table below. You will need to use the internet or a textbook to find more physical properties ofmetals.

Hint: Uses can be written more than once. An example has been done for you.

Use Physical property Brief description or explanation

jewellery lustre metals such as gold and silver are used tomake jewellery because they readilyreflect light, appearing shiny

Credits: Classroom Video / YouTube.

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Question 3

Recall: When metal atoms bond, their electrons can best be described as:

fixed

shared

delocalised

exchanged

Question 4

Research: The video mentions atoms and cations, but doesn't explain how theses terms are related. Research both terms on theinternet and explain the difference between them.

Question 5

Recall: The forces of attraction between metal cations and the sea of delocalised electrons are enough to overcome the repulsionforces between cations.

True

False

Question 6

Research: Palladium is the metal that was referred to in the Cosmos magazine article. Using a reliable chemistry site on theinternet, research the macroscale properties of palladium.

Process: Metals (P1)

Metals are comprised of a three dimensional lattice of cations surrounded by a sea of delocalised electrons (left). If youlook closely, the delocalised electrons are free to move around the lattice (right).

The above image illustrates metallic bonding. It shows the metalcations, surrounded by a "sea" of delocalised electrons. Theseelectrons are the valence electrons of each metal atom.

Metallic bonding can be used to explain each of the propertiesdiscussed in the "Gather" section of this lesson. For example,electrical conductivity relates to metallic bonding in the followingway:

When a battery is connected in a circuit, the negatively chargeddelocalised electrons migrate towards the positive end. This flowof electrons (current) enables metals to conduct electricity.

This can also be represented diagrammatically (right).

to the metallic bonding model at the top of this page.

The properties you need to consider are: malleability, heat conductivity and lustre.

Hint: The first thing you need to think about is "what are the electrons doing?". You may sketch your diagrams by hand, photograph them

and upload them below.

The Cosmos article refers to the metal palladium and its use in the form of nanoparticles. The nanoparticles are embedded into aball of polystyrene resin which is inserted directly into the tumour where it acts as a key to activate the cancer drug once it arrives atthe tumour.

Question 2

Explain: We've already spent some time looking at properties on the macroscopic scale, but what does the prefix "nano" refer to?Hint: nano-sized and micro-sized items need to be viewed under a microscope!

Question 3

Research: How are nano and micro properties of materials different from macro properties?

Question 1

Explain: In the project space below, use worded explanations and fully labelled diagrams to relate each of the following properties

Question 4

Calculate: Use the following conversions to complete the table below.

1 nanometre (nm) = 10 metres (m)

1 micrometre (µm) = 10 metres (m)

Hint: You should write answers in scientific notation where appropriate. You may indicate exponents, or powers, such as 10 as 10^2.

-9

-6

2

Item Metres (m) Micrometres (µm) Nanometres (nm)

diameter of a single hair 2 x 10-7 2 x 10-1 200

DNA 2.5

diameter of a red blood cell 7.5

diameter of a tennis ball 100000000

tip of a pencil 1000000

a water molecule 10-10

a palladium nanoparticle 1

diameter of a ball of polystyreneresin

1.5 x 102

Apply: Metals (P2)

Experiment: Determining the properties of metals

This experiment is designed to consolidate your understanding of the properties and bonding exhibited by metals. As we havediscovered throughout this lesson, there are numerous applications for metals, each of which rely heavily on the properties thatmetals exhibit. For example, palladium is used to help fight tumours and gold is used in gold leaf decorations.

You will be given a selection of materials which you will test. It is expected that you will be able to recall the physical properties ofmetals prior to commencing this series of activities and then collect experimental data to classify each material as either "metallic"

or "other".

To classify materials according to their properties.

For this experiment you will need the following:

A selection of materials: small candle, copper, sodium chloride (solid), magnesium, toothpick, zinc, sulphur, chalk, iron etc.

Multimeter

Deionised water

Moh's hardness kit (if available)

Hammer or pliers

8 test tubes

100 mL beaker

Bunsen burner

Background

Aim

Materials

Matches

Safety glasses

Bench mat

1. Describe the appearance of each material prior to experimentation.

2. Electrical Conductivity: Turn the dial on the multimeter to 20000Ω on the resistance scale. Place the two electrodes on thesample about 1 cm apart. Record the value on the screen. If it reads 0 there is no resistance and it is an excellent conductor!Test all samples.

3. Hardness: Using Moh's Hardness Kit, start with the softest mineral try and scratch your sample. Move up the scale until yoursample is scratched. Record the value corresponding to that mineral. Test all samples. (Note: Should you not have access to aMoh's Hardness Kit, scratch each material against the others using the same procedure above and organise your materials inorder from least hard to most hard. Apply a number to each.)

4. Malleability: Using the pliers, determine a ranking for which material bends most easily. Give a score out of 10 where 10 isthe easiest to bend.

5. Brittleness: Determine which samples are the most brittle. Give a score out of 10 where 10 is the least brittle. Holding ontothe sample, place it on the bench mat and hit the edge of the sample with the hammer. (Note: this ought to be done outside

and with safety glasses.)

6. Solubility: Place a small piece of each sample in a test tube. Add 20 mL of deionised water to the test tube. Heat gently withthe Bunsen burner. If it dissolved, test for conductivity.

Place all waste in the bin and return samples to the box.

Procedure

Question 1

Hypothesise: Before conducting the experiment, predict the outcome of each activity for the metals by recalling what you havelearned about the properties of metals so far.

Question 2

Identify: Write down the independent and dependent variable in each of the activities above.

Hint: The independent variable is what is being changed each time, the dependent variable is what you are measuring or testing.

Question 3

Collect: Use the project space below to present your results. You should construct a table of results which best suits the data butyou may also include photos, video or other representations.

Question 4

Classify: From your experimental data, categorise each material as either metallic or "other".

Metallic Other

Question 5

Conclude: Were you able to determine which materials were metallic? Describe what you learnt from this experiment.

Question 6

Relate: Why do you think these metals are not used in the same way as palladium to fight tumours?

Career: Metals (P2)

Imagine a homing missile snaking its way through your veins, depositing its payload of cancer-killing drugs only when itreaches its precise target-- a tumour. This is the brainchild of Asier Unciti-Broceta, a chemist who is creating innovative new waysto treat cancer.

Growing up in Spain, young Asier dreamt of becoming anarchaeologist like his hero Indiana Jones. But after studyingpharmaceutical sciences in high school and university, he foundhimself fascinated with doing research and developing newdrugs.

At the Edinburgh Cancer Research Centre, Asier spends his timeoverseeing his research group and experiments. Of course, healso makes time to think about new ideas, which is his favouritepart of his job. Asier loves how research allows him to think outof the box. A seemingly crazy idea could turn out to be genius,he says. One such example is the chemotherapy-deliveringpalladium implant you read about earlier in the lesson.

Palladium is a metal usually used to make jewellery and surgicalinstruments. But it can also catalyse a variety of chemicalreactions. This peculiar characteristic of palladium led Asier towonder if palladium-capped inserts could be used to catalysethe release of chemotherapy drugs into tumours. If Asier andhis team are successful, the implant will be able to kill cancerouscells while sparing the rest of the body from the usual harmfulside effects of chemotherapy.

Outside of the lab, Asier hasn’t quite abandoned his childhooddream. He still enjoys travelling around the world, discoveringnew places, people and food.

Question 1

Imagine: Imagine you are Asier on this voyage of discovery into new and innovative cancer treatments. How do you think this sortof research has sparked his interest in similar or different ways to the archaeological path he'd hoped to travel as a child?

Cosmos Lessons team

Education director: Daniel PiklerEducation editor: Bill CondieArt director: Robyn AdderlyProfile author: Yi-Di NgLesson authors: Deborah Taylor and Kathryn Grainger