Rates of Reaction.

To keep this investigation as accurate as possible I will keep fair

• The same conical flask- the same volume as it can cause confusion when reading the measurements resulting in inaccuracy
• To keep the amount of substances put in the same- in total we will have 50ml of substances at all times
• To have 25ml of HCL acid in flask-I will only change the amount of sodium thiosulphate and distilled water put in but this will always total up to 25ml.
• We will repeat this investigation a number of 3 times so at the end we have an average time from the 3.
• After doing the experiment we will rinse it but make sure to keep it the same by filling the flask up to 250ml, no shaking then pour down the sink. This is repeated a number of 4 times
• To make sure when measuring that they are measured as accurately as possible. In Method  I shall tell you how to do this
• Make sure that nothing extra is done to the flask after being put e.g. stirring or shaking as will alter the outcome of the investigation
• Care has to be taken that you are watching the flask at all times as you may miss the reaction happening therefore your results being imprecise
• I will also make sure that each liquid is poured into individual cylinder or else it will start reacting and spoil  your results

Equipment:

1x conical flask                                                                                            1x tile with a cross on

1x bottle of hydrochloric acid                                                               1x bottle of sodium thiosulphate

1x bottle of distilled water (with pump)                                               3x measuring cylinders

1x safety goggles                                                                                       1x stopwatch

Risk Assessment

I am now going to go over the equipment and analyse of any risks with them:

• Conical flask- there is a risk of it cracking or breaking which may cause wounds to a person. Also if broken can result in leakage of the mixture
• Tile- again like the flask can fall and shatter causing wounds
• HCL acid- this is at a PH 2 level so is corrosive and if contact with the skin occurs this will cause itchiness and swollenness. So caution should be taken with this.
• Sodium Thiosulphate- This again is like the HCL acid so again caution should be taken when handling these 2 substances
• A word of warning if  you should contact with either two substances it is important that you immediately go and wash your hands as it will reduce anything to happen to you as you are diluting it
• Distilled water-  if dropped can cause a slippery surface which can in turn result in an accident
• Measuring cylinder- can cause accident if dropped and must be used carefully as can cause contact with skin and if it is the acid or the sodium thiosulphate then this can cause an injury
• Safety goggles- for your own protection but if worn incorrectly can cause harm such as substance going into the eyes
• Stopwatch-  if broken the liquid inside it can cause a fatal injury to you

Safety

As I have said before there are risks in this investigation, safety issues concerning the equipment can be read in Risk Assessment.

But there are other possible safety factors which can occur these are

• Skin irritation – if any substance go on your hand they will cause itchiness which can upset your skin but also make any skin conditions poorer
• If swallowed can cause internal damage if does happen rinse out and drink plenty of water
• If any substances goes on clothing, pens, bags, etc, then this can cause harm for me as some acid may still be on the pen and if using it can spread to your hands so it is a necessity that you wash your hands, pens and any part of your clothing that may have had contact with the substances to be

        washed immediately

• There is a smell which would be released so anyone who may be affected should not do the observing

To make sure that I am safe during this investigation I am going to take care and put my safety and risk assessment to use.

I will take 3 readings as said in Control Variables. This is so we can collect the times then find out the average between the 3.

I will try to make this investigation as accurate as possible to ensure that my results are as thorough as can be.

Concentration Levels

As you know I will change the concentration of the mixture but I will make certain that there is 25ml of HCL acid and different amounts of Sodium Thiosulphate and Distilled Water

So here I put in diagrams of how much is needed to be put and what concentration it is

Method

1. Place the conical flask over the tile ensuring that you can see the cross clearly under the base.

2. Measure up your substances making certain that they are the correct measurements. To guarantee that they are crouch down placing your measuring cylinder on the table then eye level pour out the substance.

3. When all the substances have been measured up. Prepare to add in the substances in the order of :

• Hydrochloric Acid
• Then Sodium Thiosulphate
• Finally(when using) distilled water

4. After putting in the HCL acid prepare your stopwatch and Sodium Thiosulphate as just when you put in the Sodium Thiosulphate you should start the timer.

5. Also if you are adding the distilled water add it at the same time with the Sodium Thiosulphate and start the timer as before making certain that you shake all the contents out.

6. Keep this going place your head above the conical flask making sure your safety goggles are on. See until you cannot see the cross anymore then stop the stopwatch. Be careful as a odour will be released  

7. After the investigation go to the sink pour down the contents of the flask and fill with 250ml of cold water, then pour down sink. Repeat this 4 times.

8. Then repeat the investigation again to keep up the control variable.

What I see from my results

We can see from my results that my Prediction was in fact correct. I was correct in saying that the more concentrated solution would react the fastest.

We see that firstly that the time of reaction is 0.0247 more than 80% concentration so this shows that there is more collision of particles (see Prediction & Background). The pattern we see is that from the table and graph we see that the reaction time takes longer when the mixture is less concentrated.

We see in the line of best fit that the reaction time goes down as the concentration goes down.

Also concentration with time we see that the less the concentration the longer the time for it to react.

Conclusion

From this investigation I have learnt that my Prediction was near correct. We saw that the more concentrated solution reacted the fastest. If you look back at Background we learn of the “collision theory” in which the more particles present in an amount of space the more they will collide with each other consequently resulting in a faster reaction occurring in the conical flask.

Here is a diagram of the “collision theory” where I compare a less concentrated mixture with a more concentrated one.

But there was no salt produced as I had thought I do not know why this is but I believe a little was produced but an amount invisible to the naked eye.

From this investigation I have learnt how to measure substances into a measuring cylinder to make sure it is as accurate as possible. This is due to the fact  that  you are eye level while pouring so you know when to stop.

I have learnt that when these two substances Hydrochloric acid and Sodium Thiosulphate mix together the reaction that happens is that the solution turns cloudy, a temperature rise happens and a fishy kind of smell is also given off.

I have learnt how to handle and add in properly the substances into the conical flasks. From how to hold them without dropping, to measure them out to putting them into the conical flask and timing them finally to disposing of the final mixture.

Also I learnt of how to make sure I have the right amount of the substance required

To conclude I also learnt how to calculate the rate of reaction which is simply done by the equation:      

                                           1

                Average Time

This equation then gives you the rate in which it took in the conical flask.

Evaluation

In this evaluation I will record down all the problems which I foresaw these are:

1. As you see in the results table the result  for time 3 for 20% concentration we see that that it is anomalous f from time 1 & 2.This I believe is because we used the same flask again and again so in the end the question is did my washing take all of the solution away? Because we didn’t wash dry the water away it meant that maybe more water was added then actually needed
2. Did all of the measured out substances go into the flask? As some drops may have been left behind so for each it would be an unfair experiment. This means that the result may be inaccurate
3. I may have at one point shaken the flask or it could have had a bump this would mean that there was interference with the solution which could result in slowing/speeding up the reaction process
4. Timing- Did I see the cross completely go and did I stop the watch at the precise second. Again can cause inaccuracy and here a big one as to find out the rate of reaction you need accurate results so here is a problem
5. My goggle steamed up at one time so this meant that I didn’t properly see the cross so did I take it down properly
6. When I was washing did I as said in no.1 wash away all of the substance? As we see that it did affect my result
7. I may have mixed up the individual measuring cylinders so ending up contaminating the mixture beforehand
8. When measuring I didn’t always do the eye level measuring I only did it after my teacher told me but that was in the middle of the experiment so is measuring 100%?
9. As I said before how do I know completely that the cross has totally disappeared?

These will definitely effect my result as we see that my times have in deed gone anomalous in the investigation..

These are points that I have to put into consideration and use my resolutions

(Below)

Resolutions to problems

For most of these the main solution is to TAKE CARE when doing it as I clumsy mistake can mean the whole investigation going up in ruins

1. For this you have to take care that you do wash out the mixture as thoroughly as possible. But as to keep your control factors the same this will be hard to do but care should be taken that you do rinse away the mixture as best you can
2. Here you have to make certain that you do make all the substance go into the conical flask. Shake it all out to ensure that all of it comes out
3. Here as I have said you have to make sure that you don’t cause any bumps to the conical flask
4. This is beyond my control but there is an improved version of repeating this investigation which I will tell at the end- but here you have to be quick in watching the cross go an when you are stopping the time 1 second can make a big difference
5. When getting your goggle try to get a clean one and before each go, clean your goggle of any steam and try to have two people keeping watch on the cross so they can clarify with each other if the cross is gone and if ones goggle steam up then the other can carry on
6. As I said in no.1 this you have to try your best to 1 clean your flask out and2 keep within your fair test rules
7. To make sure you don’t mix up the measuring cylinder why not number them and label them to corresponding substances or just place each beside its substance to avoid confusion
8. This can only be rectified if the investigation is repeated but due to time limitations this is not quite possible
9. This again as I said can be resolved if you have 2 people who will agree with each other if the cross has gone

Improvements to the Investigation

Another way to repeat this test and to keep it accurate is when measuring use a weighing scale to get it spot on.

And on the investigation I would use IT to help out.  I’d get a laser to go through the conical flask to a hit a light sensor attached to a computer with a timer. When you add the distilled water and/or the sodium thiosulphate the timer starts when the solution turns cloudy the laser will no longer hit the light sensor therefore stopping the timer. So you have an accurate time.