Classic results for NaOH and HCl titration

Getting a classic set of results for the  titration of NaOH and HCl is not that difficult but it is nice when we can get students to this first time every time.

We are using the Pasco sensors and the Capstone software to capture the information.

In this experiment we are titrating NaOH against HCl.
 We set the burette dripping at a constant rate and then measure the temperature change and the pH change using probes.

The magnetic stirrer ensures the compounds are well mixed and the Sparklink Air delivers the information to the laptop where the information is captured instantaneously.
The experiment is quick to set up and easy to use, and most importantly very easy to replicate.

Knitting some Intestines

We went to the Bett Show a few weeks ago and there we saw a model of a Liver. It had been knitted so we thought we would have a go. After much searching on the net we finally found a pattern and so we have started.
The Model is life sized. We have started at the anus and rectum and we are now starting work on the large intestine. The small intestine is about 27 feet long itself and so will take a considerable amount of time to do.

Day by day the knitting goes on and the stuffing of them. The large is about half done in the picture.

Over the weeks the intestines continue to grow.








The large intestine is complete and now 20 feet or so of small intestine needs to be knitted.

Playing with Hydrogel

Adding some water to Hydrogel.
We took about 7 cm3 of hydrogel . We extracted this from a clean dry Nappy.
You Need

Disposable nappies

A disposable nappy
Scissors
A large ice cream tub or similar container
Dessert spoon or similar measure
Stirring rod
Large beaker or plastic tub to hold at least 600 cm3
Plastic gloves for those with sensitive skin
a Cut the middle section out of the nappy – the thicker piece that is designed to absorb
the urine. Discard the other piece.
b Make sure the ice cream container is completely dry - wipe it with a paper towel if
necessary. Any moisture in the tub stops the experiment from working properly.
c Wear eye protection for the next step. Put the centre piece of the nappy into the ice
cream container and gently take it apart. Small white grains should start coming away
and this is what you are trying to collect. Keep gently pulling the nappy apart until you
have collected as many of the grains as you can. Do not do this roughly or you will lose
your product and put a lot of dust and fluff into the air. Avoid breathing in any of the
dust.
d Remove and dispose of all the fluff and other parts of the nappy, keeping the grains in
the bottom of the tub. They are heavier and fall to the bottom, which makes it easier to
separate them out.
e Estimate the volume of the grains.

Now the fun Bit

f Pour them into the large beaker and add about 100 cm3 of distilled water. Stir. Keep
adding  water until no more can be absorbed and stir between each addition.
Estimate the final volume of the hydrogel.

Now even more fun

g Add a dessert spoonful of salt and stir.

Poinsettia pH paper

To make the Poinsettia pH paper:

1. Cut the flower petals (actually specialized leaves called bracts) into strips
   
2. Place the strips into a beaker.
   
3. Add enough water to cover the plant material and simmer on a hot plate. 
   
4. Filter the liquid into another container (such as a shallow petri dish) and discard the plant matter. 
   
5. Saturate a piece of filter paper with the poinsettia extract. 
   
6. Allow the filter paper to dry and cut the colored paper into test strips. 

Motion Sensors to work out Distance Speed Graphs

Using the Motion sensor here we can do a series of experiments simultaneously to record the Distance, Velocity and acceleration of the cart as it moves down the track.

Here we are using a Lego trolley with a screen at the back to reflected the ultrasound signal.

The cart can be loaded with different masses.

Here are some distance time graphs to show four different runs at four different heights.

As the trolley moves down the track its velocity increases until it crashes at the end and the velocity drops sharply to zero.

1 was the shallowest
3 was the steepest.

Hot and Cold Water Diffusion

A classic way of showing diffusion is to add a small purple crystal to water and let it diffuse. By having two set ups one with hot water at around 80C and the other at 15C ( straight from the cold tap ) an idea is given on how temperature effects the rate of diffusion.

Using a Colorimeter to follow the rate of a reaction

With a new bit of kit I have been looking at the rate of reaction of an old favourite, HCl and Sodium Thiosulphate. This system has many advantages over the usual practical, not the least being that the reaction takes place in asealed cuvette so there is no smell and the amounts of substances are very reduced.

The Pasco software (in this case Saparkvue) makes recording this a breeze, creates the tables and graphs so that the data can the analysed easily.

A small amount of the chemicals are used ( approximately 6ml per experiment. The cuvette is filled with the required mixture and the placed in the calorimeter. This calorimeter records all the wavelengths at the same time so I don't have to worry about selecting the correct one, but simply the best one at the end of the experiment.

Before the experiment is started it is necessary to calibrate the colorimeter  but a cuvette of pure water, then it is simply a task of placing the solution to be examined in the cuvette and clicking start

The results can then be exported to word with any analysis. This system seems so much better value for money than other systems I have used.