Guidelines for the Pitch Tar Drop Apparatus

The apparatus should be placed away from direct sunlight and heat (i.e. not on a windowsill or too close to a radiator). It could be placed in a foyer to engage with the wider school population. 

Teachers can choose which year group is most appropriate to be responsible for the measurements in their school. 

Each school will receive a weblink which will bring you to a form for entering your data.  

The date, time lapsed (hours) from when the plug was removed, the length of the pitch tar from the base of the funnel (mm) and the temperature should be recorded using your school specific form. There is also a Y/N question asking if a drop has dripped. This is important as it will be used for the presentation of the data on the School of Physics Pitch Tar experiment webpage.  

It is suggested to measure the length weekly at first. This is a new pitch formulation, and we cannot be sure how fast it will flow. If the flow is increasing, then measurements can be made more frequently. 

The data can be used to extract the value of viscosity.  Two scientific papers showing this are included here.

The viscosity of the pitch will be lower at higher temperatures. This is why we are asking you to record the temperature so that students can compare the rates of fall across different schools. 

The data will be available publicly for anyone to view and use.  

We are asking to you record data until the pitch has first contact with the glass dish. Once that happens you don’t need to return any more data, but you can continue to use and enjoy the apparatus for future years. You can replenish the funnel at any time by adding the fallen pitch tar back into the top of the funnel.  

To capture the drop formation as a function of time you can photograph at regular time intervals to create a time lapse video (the suggested method) or use a webcam for real time recording. You can find a simple guide for creating this video here Simple guide to making a time lapse video recording of your pitch tar experiment

Images can be posted on social media using #physics300 and the School of Physics handle @TCDPhysics (LinkedIn) or @TCD_physics (Twitter/X) and @AMBERCentre (Twitter/X). We prefer if you used LinkedIn or X. We will be able to capture these posts and repost from School of Physics and AMBER accounts. 

Possible Learning Experiences and Activities

Viscosity is the word we use to describe the resistance to flow.

Measurement of Viscosity

If we drop marbles into water, honey and cooking oil, in which will it fall most slowly?

• Take three graduated cylinders and add a liquid to each.
• Release a marble in each
• Measure the time it takes for the marble to sink to the bottom
• Repeat a number of times, and look at mean results
• Which do you think is the most viscous? Which is the least?
• Was your prediction correct?  Explain your answer.

Measurement of Flow Rate

What do you think affects the rate at which something will fall through a funnel? (‘Rate’ can mean different things – but here we mean how many grammes per second fall through)

If we drop tiny chia seeds through one funnel and larger sesame seeds through another, which will fall more quickly?   Do you think the diameter of the funnel spout would have an effect?

• Pour about 50g of each type of seed into two funnels (blocking the spout)
• Let them flow through, and measure how long it takes to empty
• Try it again, with a wider funnel spout
• Compare your results.
• Were your predictions correct? Explain your answer

In each of these activities, using a slow-motion camera might make it easier to make precise measurements of the time. 

Drawings created using Chemix.org

Shared Learning Day in March 2025.  

The event will be hosted by the School of Physics, Trinity College Dublin and AMBER on Thursday 27th March, 2025 in Trinity College Dublin. We are inviting teachers to bring two students from their school with them, more details will follow closer to the time.  

For this event each participating school is asked to prepare a poster. The poster template is provided PITCHTAR_2024_ Poster Template. The deadline for return of the completed templates is 28th February, 2025. We will format the inputs you provide to create the posters for the Shared Learning Event and each school will be able to take their poster home. Digital copies will be shared with schools for display on their school website.