Science Coursework Investigation ions

Section 1 – PLANNING

Write a detailed plan of your experiment. Make sure it is a fair test. Draw a diagram of apparatus if you like. Predict what will happen and say why, using scientific background material, which might include information from books, CD-ROMs or the Web.

Mark scheme:

For 2 marks: Plan a simple, safe experiment.

For 4 marks: Plan a fair test, choose equipment, and make a prediction.

For 6 marks: Use scientific knowledge to plan, decide what to control and vary. Make a prediction. Decide on a suitable number of measurements.

For 8 marks: Use scientific knowledge to plan, trying to be precise and reliable. Make a prediction and justify it. Use information from other sources.

List of Equipment:

Measuring cylinder

Boiling tube

Trough

Delivery tube

Goggles

Spatula

Gloves (if possible)

Boiling tube rack

Digital weight measurer

To make this experiment a fair test I will have to keep the following factors the same:

Same size boiling tubes.

Volume of Acid

Period of time

Amount of metals.

Temperature

Starting temperature of the acid

Surface area of the metals

Safety

Safety precautions are needed because I am dealing with reactive metals, which can injury. The following things need to be acknowledged to, in order to keep this experiment safe:

Ø Be careful not to knock over the rack with the boiling tubes in
Ø Be careful not to knock over other peoples vessels
Ø Care is needed when pouring acid
Ø Do not run with the vessel of acid.

Ø Wear safety goggles as I am using concentrated hydrochloric acid

Ø Do not touch the hot boiling tubes with acid reacting in it.

Ø Try to handle equipment as carefully as possible as it can be broken easily.

Ø Care to eyes and the skin besides all the other people is always vital and necessary

Ø Care in using glassware since it is sharp when broken and can cut skin

Ø Safe disposal of reagents and laboratory chemicals

Ø Care when returning all used glassware and equipment at the end of the experiment

First of all we need to check that we have all the equipment required for the experiment and after doing this we carefully set up the apparatus as shown and check that everything is in the rite order and working properly. After this we take 21g of each metal (this is necessary to make it a fair test) and place it in a boiling tube. The boiling tube should be placed in a boiling tube rack for safety reasons. After doing this we take 10ml of hydrochloric acid (Goggles must be worn for safety precautions) and pour it into the boiling tube, which has the metal in it. Following this we should insert the delivery tube into the boiling tube and start the clock. (The delivery tube should be inserted quickly so that the gas does not escape). The volume of the gas should be recorded every minute. The reading from the measuring cylinder should be taken careful keeping in mind that parallax error should not occur. (Parallax error is when an object is viewed from the wrong angle e.g. when taking a reading if we look from far right we might get a wrong reading. So prevent parallax error we should always look from the middle). The results should be neatly recorded in a ladled table. The same procedure should be repeated for each metal. Test should be repeated at least two or three times to prevent mistakes and to make the test accurate and fair.

All chemical reactions involve reactants which when mixed may cause a chemical reaction which will make products.

In my case the reactants are hydrochloric acid and magnesium. The chemical reaction takes place when the magnesium is dropped into the hydrochloric acid. The products that are formed during this reaction are hydrogen gas and magnesium chloride. The formula equation for this experiment is:

Mg + 2HCl (r) MgCl2 + H2

Magnesium + Hydrochloric acid (r) Magnesium Chloride + Hydrogen

Magnesium will react with hydrochloric acid, because it is higher in the reactivity series that hydrogen. When the two chemicals react a ...

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All chemical reactions involve reactants which when mixed may cause a chemical reaction which will make products.

Mg + 2HCl (r) MgCl2 + H2

Magnesium + Hydrochloric acid (r) Magnesium Chloride + Hydrogen

Magnesium will react with hydrochloric acid, because it is higher in the reactivity series that hydrogen. When the two chemicals react a displacement reaction will take place and the magnesium will displace the hydrogen in the hydrochloric acid forming magnesium chloride and hydrogen gas.

I predict that copper will not react with hydrochloric acid. The prediction is supported by the reactivity series it shows that copper has no reaction with dilute acid so from his we can presume that the same thing will happen with hydrochloric acid. I also predict that Magnesium will react with hydrochloric acid, because it is higher in the reactivity series that hydrogen. When the two chemicals react a displacement reaction will take place and the magnesium will displace the hydrogen (supported by the reactivity series) in the hydrochloric acid forming magnesium chloride and hydrogen gas.

Background science (including word/ formula equation for reaction)

I already know that metals react with acid. Some metals are more reactive than others e.g. Sodium is more reactive that iron.

The word equation for the reaction between a metal and an acid is:

Metal + Acid Salt + Hydrogen

In the reaction the metal takes chlorine from the dilute acid, leaving hydrogen, which form bubbles. For example:

Magnesium + Hydrochloric acid magnesium chloride

Hydrogen

Mg (s) + 2HCI(aq) MgCL (aq) + H (g)

A similar reaction of metal occurs with water. With water, the metals are taking oxygen from hydrogen. With hydrochloric acid, the metals are taking chlorine from hydrochloric acid. A similar reaction occurs between metals and dilute sulphuric acid.

I also know that higher a metal in the reactivity series the more hydrogen it will produce.

Prediction

As I already know the word equation for metals reactivity with acid is:

Metal + Acid Salt + Hydrogen

I know that hydrogen will be produced. I also know that higher the metal in the reactivity series the more hydrogen it will produce. As Magnesium is highest in the reactivity series form the metal that I have got I predict that magnesium will produce most hydrogen. I also predict that Copper will not react with any metal. I know this because copper is lower down in the reactivity series.

Info sources

Encarta Encyclopedia
Britannica Encyclopedia
Revision guide
Nottingham bluecoat school website

Section 2 – OBTAINING EVIDENCE

Carry out the experiment. Put your results in a properly labeled table. Repeating experiments gives you more marks. Take averages (means) where this is appropriate.

Mark scheme:

For 4 marks: Make enough measurements and record them.

For 6 marks: Make accurate observations, repeat them and record them clearly.

For 8 marks: Use equipment with precision. Record a sensible number of reliable measurements.

In obtaining evidence accuracy is everything and to this the following step were taken:

Set balance to zero, (use the Tare or T button)

When reading a scale, look at it at right angles

When measuring liquids, the bottom of the meniscus should be read

Repeat any readings that are obviously way out (so one does not have to include the wrong reading)

I did not make any changes to my original plan.

All the results were taken accurately and checked and rechecks for accuracy. I have collected three sets of results, which in my opinion are enough for me to draw a conclusion.

Section 3 – ANALYSING EVIDENCE

Can you draw a line graph or bar chart of your results? It may be sensible on a scatter gram to use a line or curve of best fit.

What can you conclude from your experiment? Which results tell you this?

Use your scientific knowledge to explain your conclusions. Compare your conclusions with your original prediction.

For 4 marks: Plot graphs and explain what they show. Find patterns in the results.

For 6 marks: Construct graphs with lines of best fit, to process results. Write conclusions and relate them to scientific knowledge.

For 8 marks: Use scientific knowledge to explain conclusion. Compare results with original prediction.

My results support of original predication. Which was higher the metal in the reactivity series the more hydrogen it will produce and the faster it will react that others under it.

My prediction stated that higher the metal in the reactivity series the more hydrogen it will produce. I also predicted that magnesium will produce most hydrogen and that Copper will not react with any metal. My results proved this prediction correct as, for example we can see in the results table that magnesium produced most hydrogen out of all the metals and that copper did not react with any metal.

Section 4 – EVALUATING EVIDENCE

Could you improve your experiment? What changes could you make to the method you used?

Are your results accurate? Could you have used more accurate equipment?

Are any of the results wrong, or are there some that don’t fit in with the pattern that others show? Why do you think they might be wrong?

Have you enough results to be sure that your conclusion is right?

For 2 marks: Make a comment about the experiment.

For 4 marks: Comment on the accuracy of the results, and spot any wrong ones. Suggest possible changes to make things better.

For 6 marks: Comment on the reliability of your results, explaining any bad results. Say whether you have enough results for your conclusion. Suggest improvements or further experiments to do.

I feel that I was precise when measuring volumes of hydrogen-collected. I measured the water with a measuring cylinder.

Also I measured the Hydrogen to the nearest .5 0ml. I also measured the starting temperature accurately. I measured the time to the nearest second with the stop clock.

Did I take enough readings? And are my results accurate?

I did take enough readings as I recorded the volume of hydrogen once a minute for 5 minutes, which gave me 5 results. I repeated the experiments 3 times which mean that my results are fairly accurate.

Anomalous results

I did obtain several anomalous results. These results may have been in error because I may have recorded the time at slightly different times when writing down the amount of hydrogen the inaccurate results could be because while doing my experiments we moved rooms several times and that could have cause difference in temperature, atmosphere and equipment. Another reason can also be that while doing the experiment the measuring cylinder might have been moved slightly and would have cause a misreading.

Improvements to my experiment

I would like to use large amount of hydrochloric acid so my results can be more accurate. I would also like to do displacement reaction it will help me in knowing which metal is more reactive than other. My results are accurate because I repeated them 3 times.

More accurate equipment?

To take my experiment to the next degree I would like to use a measuring cylinder from which I can measure more accurately the amount of hydrogen in the measuring cylinder.

Wrong results and why?

According to my results iron reacts more than zinc but if we look at the reactivity series zinc is above iron, which means that there is something wrong with the results. Iron might have reacted more than zinc this might be because zinc may have a thin layer of zinc oxide around it.

Factors

The factors that I can consider which will help in being more accurate in my further experiments. All the following have affect the rates of reaction of my experiment:

Concentration of acid

This could affect the rate of reaction because the higher the concentration of the acid then the more acid particles per 100cm3 so more collisions per second and then there will be more successful collisions per second.

Temperature of the acid

If the starting temperature of the acid is different each time the speed at which the acid particles collide with the metals will increase more the higher the temperature goes. This means the acid particles move with more energy, which means they will collide with the magnesium with more energy, which will give more successful collisions per second.

Surface area of the metals

If the metals had a bigger surface area each time the experiment was done, then the acid particles will have a bigger area to collide with, so more collisions will occur every second and the more collisions per second than the more successful collisions per second.

Type of acid used

If you changed the type of acid then the rate of reaction would change. Hydrochloric, Sulphuric and Nitric acid all would produce a different rate of reaction, so if I do change the type of acid then all three kinds would produce a different set of results.

Key factor

The factor that I would most like to improve on is the concentration of the acid. I choose this because several different concentrations can be made up before the experiment and they will able me to be more accurate. There will be several different concentrations of acid, which will give me a wide range of results, which will be reliable and reproducible.