Good Morning to everyone out there in Labbieland! I hope this post finds everyone well!
I have a teacher trying to make up a prac assessment task for year 8's involving perspex tubes (12mm diameter), sealing one end, filling with a slightly viscous liquid, and timing how long it takes ball bearings of different diameter to drop to the bottom. He is looking for something that will slow the descent down by only a few more seconds than water so the liquid doesn't have to be very thick. The other criteria is that preferrably the liquid is water soluble (the students have to clean up after themselves for the next lot through so nothing too messy) and cheap. Any ideas?
I am going to try a glucose solution (start with 10%) and see how it goes but was wondering if you, my brains trust, could come up with an easier/better/minimal fuss type of solution!
Maybe glycerine/glycerol, though you could go through a lot of it at $ 18 odd for 500 ml from a chemical supplier. Could be cheaper at the supermarket.
I have 4 x 1cm tubes sealed and filled with water, glycerine, ethanol and an unknown ( glycerine) for viscosity in senior chem.
Why can't you recycle what ever you use so the next lot of kids can use it too? Have a recycle bucket that they can tip into and then they can wash up.
Hi, I have made up similar tubes that are sealed at both ends and have an air bubble in them and the students time the air bubble rising. I have solutions in the tubes made of water, Cook oil, glycerol, radiator coolant, parrifin oil.
Took along time to make up and to make sure all the bubbles are the same etc but it works.
Trish
Thanks for ideas, they are really good. If the glucose doesn't work then we'll try glycerol. And if that doesn't work as well as we'd like it to, I guess we'll keep on trying until we get what the teacher wants. In the meantime, all your input is really appreciated.
Thanks again,
Lou P.
We use the Clag Clear Gum for viscosity pracs. Buy it in 5 litre containers. Bit sticky but is easily recycled. If it is too resistant you could probably add a small quantity of water. We also use the clear gum glue for making volcanos out of newspaper built up around a container. Kids paint the volcanoes and make lava from bi-carb, vinegar and red food dye. If the glue dries on the benches or in any container/beaker it can be peeled off easily.
Lyn.
After trial and error our year 8 prac assessment task has been settled. The students will time how long it takes for a ball bearing to fall down a tube 50cm in length. The mediums will be water, 10% glucose soln and 50% glucose soln. Surprisingly enough there is a difference of up to a minute between water and 50% glucose, so it fits the criteria required of the students repeating an experiment, taking measurements and then transferring data onto a graph or a table.
So many thanks to my brains trust, your suggestions were duly noted and considered.
I'll let you know how it goes mess wise!
Lou P.
Another solution for consideration is Tomato Sauce nice and viscous.
Cheers,
Robb.....
Dr Robert Crosdale. MRACI. NSS. NSSA. NASA.
Ph.D (Chem), Post Grad Ph.D (Physics), M.Ed, B.Sc (Hons), Dip. Appl. Sc. (Chem)
Lake Munmorah High School.
University of New England.
University of New South Wales.
University of Newcastle.
To understand the Universe from our perspective, we need to look towards our own backyard first for answers.
OMG I think I might die.... All week I have seen this topic on the board, but haven't had time to read it... and until just now I have been reading VICIOUS LIQUIDS Only realized half way through the posts that it was VISCOUS liquids
Only realized half way through the posts that it was VISCOUS liquids 
