Science Buddies: "Ask an Expert"

Hello, My 10th grade science fair project topic is 'Does the temperature of a liquid effect its viscosity?'

Firstly, i was wondering if there was anyway i could make this topic a little harder or if there is something related that is more challenging?

Also how would i conduct this experiment (what would the variables be?, what liquid could i use?)

Also how would i change the temperature of the liquid? can i use a bunsen burner to heat it?

Thankyou very much, any help at all is greatly appreciated!

Hi -
It is an interesting topic and one way to make it higher level - more challenging, would be to investigate the change in viscosity of each liquid due to temperature - and then see what happens to those changes when you add solutes to your liquids making them solutions.

You will need to do some research yourself to decide which liquids (solvent) to test and what substances (solutes) you want to add to make solutions.

Then you can test the effect of temperature on the pure solvent and then the solutions.

Make sure you understand what the control factors need to be in your experiment and what your variables are.

Good luck!

Hi Hanjan,

I like Yvette’s idea of investigating the effects of various concentrations of solutes on the viscosity of a liquid. That is a bit more interesting than temperature since it is already known that temperature has a marked effect on viscosity: http://www.kayelaby.npl.co.uk/general_p ... 2_2_3.html

One liquid that I can think of that is very viscous and safe to use is glycerol. You could make solutions of glycerol in water to reduce its viscosity and then add various concentrations of a solute such as sodium chloride and compare viscosities at different temperatures.

Honey would be a nice sweet liquid to test the viscosity of, but it is not a single chemical compound as glycerol is.

Measuring viscosity quantitatively is not easy. There are instruments that can be used to measure viscosity but they are very expensive and specialized. I looked up ways to do it cheaply and found some information. I have never done this so cannot say how reliable or correct these methods might be:
http://www.kayelaby.npl.co.uk/general_p ... 2_2_3.html

See if any of these ideas appeals to you then repost and we will help you ask a good question with good experiments and controls.

Sybee

Hello there,

The previous experts have already given you excellent advice, and I like both of their ideas also! In terms of changing the temperature of the liquid, instead of just heating it with a bunsen burner to observe the effects of higher temperatures, maybe you can also try cooling the solutions in an ice bath or something to see how cooler temperatures affects the viscosity of your solutions as well. Other experts, are there better ways of cooling solutions besides using an ice bath?

Let us know if you have anymore questions as you develop your question/hypothesis further. We'd be happy to help you brainstorm and/or provide feedback!

Best,
Connie

If you want to cool a sample below 0C, use ice with sodium chloride. A 10% solution of salt will give 70u -6C. A 20% solution, -16C.

If you want to really cool it down, get some dry ice and put it into an insulated container of rubbing alcohol [isopropanol]. This will give you a temperature of about -80C. Only handle dry ice with heavy gloves and ALWAYS wear your safety glasses. http://en.wikipedia.org/wiki/Cooling_bath

The main problem that I see you will have is quantitating viscosity. How did you plan to measure the viscosity of your solutions at various temperatures?

Sybee

Sorry. That second sentence should have been: A 10% solution of salt will give you -6C. A 20% solution, -16C. http://science.howstuffworks.com/nature ... d-salt.htm

Sybee

I agree with everything SciB has said earlier and those are great ideas. I also think that to measure viscosity, one thing you can do is get a tray (like a lunch food tray) and use a couple books to hold it up on one side. Then, using an eye dropper, put a bit of your solution onto the tray and measure how far it travels down the tray in a given amount of time. You can use this to comparatively determine two viscosities. If you would like more exact measurements, you would need to use a rheometer or a viscometer.