Metals: What makes them unique?

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. ...
Author: Gary Elliott
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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. We even use them to describe stages of our development on that journey. The Iron Age and the Bronze Age, for example, give a quick picture 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 a way 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 to place the drug in only the cancer cells, there is less chance the patient’s healthy cells will be affected. And it looks like scientists have found 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 a chemical that prevents it from activating after the patient has taken it. When the drug encounters the palladium, the metal acts as a catalyst to remove the chemical sheath, releasing the cancer drug at exactly the right place so it will kill cancer cells but not hurt healthy 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 just discovering.

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 an active 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 and physical 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 a brief description of each in the table below. You will need to use the internet or a textbook to find more physical properties of metals. Hint: Uses can be written more than once. An example has been done for you. Use

Physical property

jewellery

lustre

Loading

Credits: Classroom Video / YouTube.

Question 3 Recall: When metal atoms bond, their electrons can best be described as: fixed shared delocalised exchanged

Brief description or explanation metals such as gold and silver are used to make jewellery because they readily reflect light, appearing shiny

Question 4 Research: The video mentions atoms and cations, but doesn't explain how theses terms are related. Research both terms on the internet 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 repulsion forces 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 the internet, 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 you look closely, the delocalised electrons are free to move around the lattice (right).

The above image illustrates metallic bonding. It shows the metal cations, surrounded by a "sea" of delocalised electrons. These electrons are the valence electrons of each metal atom. Metallic bonding can be used to explain each of the properties discussed in the "Gather" section of this lesson. For example, electrical conductivity relates to metallic bonding in the following way: When a battery is connected in a circuit, the negatively charged delocalised electrons migrate towards the positive end. This flow of electrons (current) enables metals to conduct electricity. This can also be represented diagrammatically (right).

Question 1 Explain: In the project space below, use worded explanations and fully labelled diagrams to relate each of the following properties 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 a ball of polystyrene resin which is inserted directly into the tumour where it acts as a key to activate the cancer drug once it arrives at the 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 4 Calculate: Use the following conversions to complete the table below. 1 nanometre (nm) = 10-9 metres (m) 1 micrometre (µm) = 10-6 metres (m) Hint: You should write answers in scientific notation where appropriate. You may indicate exponents, or powers, such as 102 as 10^2. Item diameter of a single hair

Metres (m) 2x

10-7

Micrometres (µm) 2x

10-1

DNA

Nanometres (nm) 200 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 diameter of a ball of polystyrene resin

1 1.5 x 102

Apply: Metals (P2)

Experiment: Determining the properties of metals

Background This experiment is designed to consolidate your understanding of the properties and bonding exhibited by metals. As we have discovered throughout this lesson, there are numerous applications for metals, each of which rely heavily on the properties that metals 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 of metals prior to commencing this series of activities and then collect experimental data to classify each material as either "metallic" or "other".

Aim To classify materials according to their properties.

Materials 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

Matches Safety glasses Bench mat

Procedure 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 the sample 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 your sample is scratched. Record the value corresponding to that mineral. Test all samples. (Note: Should you not have access to a Moh's Hardness Kit, scratch each material against the others using the same procedure above and organise your materials in order 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 is the 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 onto the 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 with the Bunsen burner. If it dissolved, test for conductivity. Place all waste in the bin and return samples to the box.

Question 1 Hypothesise: Before conducting the experiment, predict the outcome of each activity for the metals by recalling what you have learned 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 but you 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 it reaches its precise target-- a tumour. This is the brainchild of Asier Unciti-Broceta, a chemist who is creating innovative new ways to treat cancer.

Growing up in Spain, young Asier dreamt of becoming an archaeologist like his hero Indiana Jones. But after studying pharmaceutical sciences in high school and university, he found himself fascinated with doing research and developing new drugs. At the Edinburgh Cancer Research Centre, Asier spends his time overseeing his research group and experiments. Of course, he also makes time to think about new ideas, which is his favourite part of his job. Asier loves how research allows him to think out of the box. A seemingly crazy idea could turn out to be genius, he says. One such example is the chemotherapy-delivering palladium implant you read about earlier in the lesson. Palladium is a metal usually used to make jewellery and surgical instruments. But it can also catalyse a variety of chemical reactions. This peculiar characteristic of palladium led Asier to wonder if palladium-capped inserts could be used to catalyse the release of chemotherapy drugs into tumours. If Asier and his team are successful, the implant will be able to kill cancerous cells while sparing the rest of the body from the usual harmful side effects of chemotherapy. Outside of the lab, Asier hasn’t quite abandoned his childhood dream. He still enjoys travelling around the world, discovering new 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 sort of 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 Pikler ​Education editor: Bill Condie Art director: Robyn Adderly Profile author: Yi-Di Ng

​Lesson authors: Deborah Taylor and Kathryn Grainger