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How viscous is your ketchup?

Thursday 25th January | 2 comments

Today we tested the viscosity of different liquids.

Viscosity describes how thick and sticky a liquid is.  Something which is very viscous is very thick due to ‘internal friction’.

I love my gravy very viscous.  I also like my custard to be particularly viscous!  But what about ketchup? Do you prefer a thick ketchup or a runny ketchup? What is the best viscosity for the perfect ketchup?  The debate continues….

Aside from the crucial discussion over how we like our sauces, we did actually do some ‘sciency’ things!  We conducted an experiment to compare how the viscosity of a liquid would affect the time it would take to travel along an angled surface. We experimented on 4 different liquids: ketchup, honey, oil and skin lotion.

Most pupils were correct in predicting that the more viscous the liquid, the longer it would take to travel.  There were mixed opinions over which liquid would be most/least viscous.

To test our predictions we first ensured we had created a fair test.  We made sure there was only one variable – the type of liquid.  Everything else we kept completely the same (the angle of the board, the amount of liquid used etc).

We repeated our experiment 3 times to ensure our results were accurate.  It turns out that the skin lotion is the most viscous, whilst the oil is the least!


2 responses to “How viscous is your ketchup?”

  1. Rhys mum says:

    Rhys has been experimenting at home too with his magnetic thinking putty. He has mercury which can change from a solid to a liquid with heat. We have both had fun seeing how the magnet affects the murcury instantly and over time.

  2. Peter Harris says:

    This was a super bit of investigating: well done Miss Bradley and 5B.

    When I was a boy, my family ‘adopted’ a man who had no family and had been brought up in a Children’s Home in Scotland. He lived with us and worked in the kitchen of the restaurant that we ran. He made the runniest custard you have ever seen: it was like water! Miss Bradley would have hated it (and so did we!). This level of custard viscosity was what he had grown up with in the Children’s Home: I imagine it was that thin to save a tiny bit of money. I think it may have even been watered down. Nowadays, Children’s Homes are much better funded and Looked After Children are, I hope, better cared for. In fact, Ofsted inspectors are coming to Leeds next week to check up on how well the city cares for the children that are Looked After.

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