Applications of Science in the Real World

Malvern Instruments: what do we do?

› Design & make scientific instruments for measuring the properties of materials

Size of particles

Shape of particles

Viscosity – how easily fluids flow

Chemical identification

Why do people want to measure particle size?!

› Particle size affects the properties of the material We want to understand how our material is going to

behave!

› Some examples….

Paint• How glossy is the paint finish?

Ink• Will the ink flow smoothly onto the paper?

Coffee• How will it taste?• How long does it take to brew?

Medicines – tablets & liquids• How long will it take to dissolve in my stomach?• Are there the same proportions of ingredients in

each tablet/bottle?• Will any of the ingredients change over time?

Cement• How strong is the cement?• How quickly will it set?

› Later, we’ll have a look at one of my favourite samples….

› But first for some science!

So, how do we measure particle size…?

› First, prepare the sample... We want the particles separate from each other – “dispersed”

Can disperse the sample “dry”• Uses a vibrating plate to spread the sample out• Uses a vacuum cleaner to draw the sample into size

measuring instrument

Can disperse the sample “wet” • Mixes the sample with a liquid to separate out the particles• Pumps the sample into the size measuring instrument

› Then, shine a red laser at the dispersed particles

› The particles scatter the light in different directions - “Diffraction”

› The direction that the light is scattered – or angle of diffraction - depends upon the size of the particles...

› Large particles don’t change the light direction very much

› Small particles scatter the light in many more directions

› From detecting where the light goes, we can calculate the PARTICLE SIZE!

Measurement cell Focal plane detectors

Side scatter detectors

Back scatter detectors

633nm red laser

Precision folded optics

› Allows us to take lots of images of the sample too!

Is there anything weird in our sample?

Is our sample properly dispersed?

We can find out something about the SHAPE of our particles, too!

Imaging Instrument

Camera from an iPhone!

Blue Light Emitting Diode (LED)

› Now for an experiment....

Chocolate Experiment

Chocolate A Chocolate B

Chocolate Experiment

› Did you notice that the more expensive chocolate has a smaller particle size?

› Why might this be? (Think about how chocolate is made – where does it come from?)

› [HINT - Cocoa beans need to be ground up before they are used in making chocolate]

› It costs money to grind up cocoa beans

› So the longer a chocolate maker spends doing it, the more expensive the process is!

› BUT, the longer the chocolate maker spends grinding up cocoa beans, the smaller the chocolate particles are

› AND, the smaller the chocolate particles are, the smoother the chocolate feels in your mouth!

› = better chocolate!

› The imaging device also indicates a difference in the SHAPE of the chocolate particles:

› What is the difference between the two chocolate types?

› What do you think might be causing it...?

Bonus Question!