Archived

This topic is now archived and is closed to further replies.

m.k.2015

Chem IA Urgent help

Hello everyone,

I am stuck here and need urgent help. We had to design an internal assessment about viscosity, therefore I decided to investigate how viscosity is affected as the number of Carbons in a homologous series increase. Hence, I just calculated the time taken for 15 ml of each solution to drop of a burette. The problem is, I do not think that this is hard enough! and I believe that calculating the time only would not get me top marks, so am I right? The other thing is that I am really stuck on the uncertainties, I have only used a stopwatch, a burette, and a beaker to measure the amount of solution I have .. How do I calculate my uncertainty

Please help asap, Thank you so much in advance :)

Share this post


Link to post
Share on other sites

well to calculate uncertainty you need to find the percentage errors of the apparatus u used during the data collection and then change them to absolute value

the formula of the percentage error = ( uncertainty divided by the actual measurement) * 100%

Share this post


Link to post
Share on other sites

I did viscosity for one of my IAs and used time to represent that. I lost the majority of my marks. My teacher said that you actually have to use and include the formula linking time to viscosity and directly calculate the viscosity.

You can find the uncertainty for the equipment you've used (burette, beaker, stopwatch) either by seeing if it's written onto the equipment itself (it often is), or looking at the uncertainties given in a textbook (I used the Pearson publication with authors Derry, Connor and Jordan). Hope this helps! :)

Share this post


Link to post
Share on other sites

I did viscosity for one of my IAs and used time to represent that. I lost the majority of my marks. My teacher said that you actually have to use and include the formula linking time to viscosity and directly calculate the viscosity.

You can find the uncertainty for the equipment you've used (burette, beaker, stopwatch) either by seeing if it's written onto the equipment itself (it often is), or looking at the uncertainties given in a textbook (I used the Pearson publication with authors Derry, Connor and Jordan). Hope this helps! :)

What do you mean by connecting viscosity directly to time?

Share this post


Link to post
Share on other sites

I haven't studied the topic yet so can't help with the lab

For uncertainties, our teacher told us to divide the smallest value that the instrument can measure by half to obtain the uncertainty value (at least for analog instruments)

Share this post


Link to post
Share on other sites

I decided to investigate how viscosity is affected as the number of Carbons in a homologous series increase. Hence, I just calculated the time taken..

Since you said that you're investigating viscosity.. just calculating the time taken will not allow you to get the data to actually investigate viscosity. Viscosity and time taken are two different things. In your method and background information you need to include, explain and use the formula linking time and viscosity - This is a picture of one formula that I've found - notice how you can actually work out a figure for viscosity itself. Hope this makes sense.

In case you were interested, I got a 4/6 for my Design on Viscosity without using the formula - I lost both marks in "Developing a Method for Collecting Data" as I only collected data of the time taken, which was not my RQ - to calculate viscosity.

1 person likes this

Share this post


Link to post
Share on other sites