Science in Action - Sample Essay

I aim the find out whether the concentration of acid effects the amount of gas given off in a set amount of time between hydrochloric acid magnesium ribbon. Prediction I predict that the higher the concentration, the quicker the gas will be given off. The atomic collision theory describes how the reaction quickens. I looked up the collision theory in a textbook “Science in Action”, and found the following information.

The collision theory explains how a reaction can only take place when reactive particles meet, under certain conditions. It stands to reason that if you have more reactive acid particles (a higher concentration of particles) in the same place, they are more likely to collide with another particle, and react. However, other aspects also affect the reaction, but are all made more likely if there are more molecules.

For the molecules to react they have to have  Enough energy to achieve an activated complex. This enery that they need is activation energy. The right orientation for the reaction to take place. ] Also, when these reactions take place quickly, the produce a lot of heat, so if the reactions do happen more quickly with the stronger acid, they will be quickened still be the increase in heat. This increase in energy makes the particles vibrate quicker, and therefore collide with other particles, again increasing there chance of reaction.

I also think that when I double the strength of the acid, the rate of reaction will double because the amount of chorine atoms available for the magnesium to react with will have doubled, therefore the amount of chorine atoms reacting with the magnesium will double, and because there are twice as many particles reacting, the rate of reaction will be twice as much. Apparatus I will need A test tube A stop clock with an accuracy of 1/10s  Magnesium ribbon Hydrochloric acid (0. 5 – 2. 5 mole) Gas Syringe Method.

From looking at textbooks and asking my teacher, I found that there are two ways measure how quickly the reaction was taking place. I could either measure the amount of hydrogen given off, or I could observe the change in weight, as the hydrogen was given off. I decided to measure the ammount of gas given off, because I knew that a change in wright would require equipment that was acurate to many decimal places, and the school did not have this equipment. I will set up the apparatus as follows I have used this method as some research I have found that this is the most widely used method.

I will drop the 2cm magnesium into the hydrochloric acid and start the timer. I will then shout out the amount of gas (hydrogen) in ml at certain intervals, determined by the strength of the acid. I have changed the time intervals because I would have to mark the results every 2 seconds for the 2. 5 mole acid, to get accurate results, but it would be pointless recording this accurately from the 0. 5 more acid. I am using 2cm of magnesium as my preliminary tests show that it keeps the reaction quick and is easier to work with.

For my preliminary test I tested different lengths of magnesium ribbon to see how long it would take them to dissolve completely in acid. I did this so I would know how much magnesium ribbon to use in the final experiment. I used all the lengths with 0. 5 and 2. 5 mole acid. I did this because I wanted a sensible length for both, with the 0. 5 mole time being short enough to be sensible, and the 2. 5 mole time being long enough to make the recording accurate. I tested length of magnesium from 0. 5 to 4, in 0. 5 cm intervals.

I did this because a 1cm difference would be too large to choose between and any smaller than 0.5 would make the measuring of the pieces a difficult task, and 1mm would not really make a difference in the amount of time taken. I would not repeat the experiment, because the results do not have to be very accurate, but they will only need to give me a rough outline of quickly magnesium dissolves. These were my results. Acid Strength (mole) Length (cm) Time (s) Acid Strength (mole) Length (cm) Time (s) 0As I didn’t repeat the experiment, I will put these results in a graph.