What is the viscosity of golden syrup?

30th January 2003

Viscosity is the speed of the flow of a liquid of gas. Viscosity is a factor which controls the liquid/gas’s resistance to flow. The lower the viscosity of a fluid, the runnier it is.

An Irish physicist George Gabriel Stokes (1819-1903) invented a method of measuring viscosity by timing a ball falling at a constant speed through a liquid. Stokes studied the forces exerted on a spherical object, namely a ball bearing as it moved through a fluid, or when a fluid moved past it. Stoke then came up with a relationship called Stoke’s law to describe the viscous drag:

=Radius of the sphere

=Velocity of the fluid

=Coefficient of the fluid (viscosity)

To obtain the viscosity the following equation can be used:

When a body moves with constant velocity through a fluid, it experiences a frictional drag force which opposes its motion. For a sphere of radius r when moving with velocity v in a fluid of viscosity h, this frictional force is equal to 6p hrv.

## Diagram of forces on the Ball Bearing Upthrust Viscous drag

Weight

The SI units of viscosity are Nsm-2.

AIM- To investigate the viscosity of golden syrup, and how factors such as temperature of the golden syrup affect the viscosity.

Before I carry out the experiment I will need to know the following:

- Temperature of the syrup- I will find this by using a thermometer and heating the syrup in a water bath until the desired temperature is reached.
- Density of steel- I will find this out by using the formula Density=mass/volume.
- Size and mass of ball bearing-I will find the size of the ball bearing by using a micrometer screw gauge. To find the diameter. I will find the mass of the BB by using scales.

I will use the same densities for BB and the syrup, as it will not vary a great deal.

APARATUS-

- Two ball bearings of different sizes and masses.
- Three water baths
- 0.2M cubed of golden syrup
- Large test tube
- Clamp and retort stand
- Thermometer
- Stop clock
- Ruler
- Magnets

The ball bearing size and mass, and the temperature will be my independent variables. The viscosity and velocity of the ball bearing will be the dependent variables.

I will be using 2 ball bearings with different sizes and masses. This was I will be able to rule out anomalous results, for example is the ball bearing is too light it may just sit on top of the syrup. If it is heavy, the terminal velocity may be so high it may travel through the syrup so fast I would not accurately be able to measure the time taken. I am using golden syrup as from my background knowledge I know it is very viscous at room temperature, and its viscosity will change dramatically with any temp change. I will be using water baths to heat up my syrup as their temperature will remain constant, and I will be able to choose the desired temperature. If I was too use a Bunsen burner the water would not remain at a constant temperature, which would make my results inaccurate, as all the tests would be done at different temperatures. I will be using a large test tube to hold my syrup as I will easily be able to measure how much syrup I put in there. I will use magnets to get the ball bearing out of the syrup, as this will involve minimal loss of syrup and mean I can use the same ball bearing for each experiment, this will help rule out anomalous results caused by using different balls.