# Begbroke Nano Teachers’ Day

These activities aimed at finding ways of experiencing the nano world and gaining confidence in using numbers to explain what we can’t see.

We have nanodetectors built into our bodies. Our noses are particularly good. We can smell something such as dilute perfume without actually seeing it.

To prove this we were given some scented food colouring. Using a Pasteur pipette we carefully measured 1 ml of the food colouring and added it to tube number 1. We shook the tube thoroughly to make sure there was an even colour. We had a sniff of tube 1 and recognised the smell from the original food colouring.

We then took 1 ml of liquid from tube 1 and added it to the next tube. Gave it a good shake to produce an even colour and had another sniff.

We kept on doing this:

Diluting tube 1 into tube 2, tube 2 into tube 3, and so on, until we had diluted tube 8 into tube 9. At each stage, we repeated the shaking and sniffing before doing the next dilution.

We found we could small the food colouring long after we had stopped seeing it.

What’s happening?

In each tube the food colouring is ten times more dilute than the previous tube. By the time we reached the ninth tube the original food colouring has been diluted by a billion times, so for every part of food colouring there are a billion parts of water.

This experiment illustrates the sensitivity of our senses. Our sense of smell allows us to detect very dilute amounts of food colouring after we’re no longer able to see any trace of it. We can only see relatively large objects, but our sense of taste and sense of smell can detect individual molecules which are just tens of nanometres in size.

Activity 2

What is my height in nm?

Well my height was measured as 1.59m. This means my height is 1 metre, 59 cm and 0 millimetres. My height in millimetres is 1590 millimetres. Therefore my height is 1590,000,000 nanometres.

Activity 3

Specific surface area activity

We measured the dimensions of a cube and found that it was 2cm x 2cm x 2cm. Its edge was 2cm and its face area was 4cm^2. As it has six faces its surface area was 24cm^2 and its volume is 8cm^3. Its surface area to volume ration is 24/8 = 3. We then took eight cubes to make an 8 stack. In this case the surface area became 34 faces x the area of one face = 136 cm^2

The volume of the 8 stack was 16 x 2 x 2 = 64cm^3

The surface area to volume ratio became 136/64 = 2.125

This activity shows that the bigger the particle the smaller the surface area to volume ratio becomes. Now if we take our eight stack and arrange it as above its surface area becomes 24 x 4 = 96 cm^2 and its volume becomes 4 x 4 x 4 = 64cm^3. The surface area to volume ratio becomes 96/64 = 1.5. The volume stays the same but the surface area doesn’t. The surface area to volume ratio therefore changes.

Activity 4

This was some card sorting activities. Firstly we had to match the size to the object. Then we had to match ratios:

If a nanoparticle equals a football then

A virus equals a human being A red blood cell = a rugby pitch

A doughnut = Italy

A chicken = The Earth