The temperature change - Sample Essay
Metals can displace other metals from their salts. A metal, which is higher in the Reactivity Series, will displace a metal, which is lower in the Series from a salt. As zinc is higher in the Reactivity Series I predict that it will displace copper from it’s salt. Transition Metals Zinc and copper are both transition metals and so are found between groups 2 and 3 of the Periodic Table. Transition metals have high melting points, high densities and colourful compounds. Copper (II) sulphate forms a blue compound. Transition metals and their ions are often used as catalysts.
Vanadium (v) oxide is used as a catalyst in the manufacture of sulphuric acid. Redox Reactions Oxidation is the gain of oxygen or the loss of hydrogen or the loss of electrons. Reduction is the loss of oxygen or the gain of hydrogen or the gain of electrons. Since oxidation never occurs without reduction, we call these reactions redox reactions. The copper gains electrons – this is reduction. The zinc loses electrons – this is oxidation. Exothermic and Endothermic Reactions An exothermic reaction is one which gives out energy to the surroundings, usually in the form of heat and usually shown by a rise in temperature.
An endothermic reaction is one which takes in energy from the surroundings, usually in the form of heat and usually shown by a rise in temperature. I know that the reaction between zinc and copper sulphate is an exothermic reaction. This can be shown using an energy level diagram. The products are at a lower energy than the reactants. The difference in height represents the energy given out in the reaction. The initial rise in the line represents the energy needed to break the bonds within the copper sulphate compound.
This is the activation energy. I am going to investigate the temperature change in the reaction between powdered zinc and copper sulphate, which is an exothermic reaction. I am going to conduct my reactions within a polystyrene cup with a lid to reduce the amount of heat lost to the surroundings during the reaction. I predict that 1. 3g of zinc (see my preliminary) should give me the highest change in temperature. As I am not using exactly 1. 3g of zinc I predict that either 1. 25g or 1. 5g of zinc will show the highest change in temperature.
After this mass I predict that the change in temperature will either decrease or level off as I think that a copper layer will form on the zinc, causing it to become less reactive. During my experiment I must ensure a fair test. To do this I will keep the concentration of the copper sulphate the same, I will use the same polystyrene cup and lid in each experiment and I will time each experiment for the same period of time (1minute). I must also ensure that I use the same balance in each test as the accuracy of different balances often varies.
After completing a reaction I will wash the polystyrene cup to avoid contamination before beginning the next reaction. The variable in each experiment is the amount of powdered zinc used. I am going to repeat my experiment three times to gain a reliable average result for each amount of zinc used. Preliminary I completed a preliminary experiment to see how much copper sulphate solution I would need to use in the experiment. I wanted to use the minimum amount so not to be wasteful yet I had to ensure that the bulb of the thermometer was covered.
I completed my preliminary experiment using 1g of zinc and 40cmi?? of copper sulphate solution. In my preliminary experiment I also had to decide on an appropriate time for leaving the reaction to take place. I decided on a minute. I set up my preliminary experiment and took the temperature of the solution as I added the zinc. After a minute I took the temperature again and calculated the change in temperature. Amount of Zinc (grams) Start Temperature (i?? C)