✅ 4. Required Practical: Temperature Changes During Neutralisation (C7) Flashcards
What is the Aim of this Practical
To investigate the variables that affect temperature changes in reacting solutions, and to be able to find the maximum temperature change during the neutralisation for certain reactants (such as Hydrochloric Acid (HCl) and Sodium Hydroxide (NaOH)).
What is my Hypothesis on how Temperature Changes During Neutralisation Practical
Overall, I think that after the zinc is added to the copper sulphate, the temperature of the solution will increase more as the mixture is stirred. This means that I believe that the solution will have a positive maximum temperature change.
Health and Safety for on how Temperature Changes During Neutralisation Practical
Dilute acids and alkalis may irritate the skin or eyes - so avoid contact with skin, rinse off skin if necessary, wear eye protection
Solutions of metal salts (used in displacement reactions) and is dangerous to the environment - so dispose of metal salt solutions as advised by teacher, some metal salts are collected for safe disposal rather than being poured down the normal drain.
Equipment for this Practical
- polystyrene cup
- thermometer
- 250 cm3 glass beaker
- measuring cylinder
- top pan balance
The Method for the How Temperature Changes During Neutralisation Practical
- Place the polystyrene cup inside the glass beaker to make it more stable.
- Measure an appropriate volume of each liquid, eg 25 cm3.
- Place one of the liquids in a polystyrene cup.
- Record the temperature of the solution.
- Add the second solution and record the highest or lowest temperature obtained.
- Change your independent variable and repeat the experiment. Your independent variable could be the concentration of one of the reactants, or the type of acid/alkali being used, or the type of metal/metal carbonate being used.
What is the Independant Variable
In this experiment, it seems as the Independant Variable is the Volume of NaOH added because it is the variable that his altered throughout the experiment to see the effect it has on the time.
What is the Dependant Variable
The Dependant Variable is the Temperature that is being used each time. This is because the dependant variable is the variable that is being tested and measured for.
What are the Control Variables
The Control Variables are the Volume/Concentration of HCl, the level of insulation, the lid and cup, and the amount of mixing. These are control variables because these are kept the same throughout the experiment to ensure thst it is kept as a fair test.
Describe And Explain Of The Graph for this Practical
Initially, it’s clear that the temperature of the solution increases with the volume of NaOH added as the temperature has risen from 20°C up to 33.6°C after 30cm^3 of NaOH was added. Here, the temperature will rise due to heat given off in the reaction, as less energy is required to break down the bonds, than what is formed in the product, resulting in the excess energy (this makes it an exothermic reaction).
However, beyond adding anything more than 30cm^3 of NaOH into the Hydrochloric Acid instead resulted in the temperature going down as the temperature drops from 33.6°C to 30.5°C between 30cm^3 and 50cm^3 of NaOH. The temperature would’ve decreased here because more energy is required to break down the bonds, than what was formed in the product (making this bit into an endothermic reaction).
What Conclusion can be made from this Practical
The bigger the temperature change in the reaction, the more energy is absorbed or released. Remember that endothermic reactions absorb energy from the surroundings, and exothermic reactions transfer heat into the surroundings; therefore making this an endothermic reaction.
Evaluation of this Practical
The biggest source of error in this experiment is unwanted heat transfer. Using a lid can help to reduce this. On top of this, it’s also important that a sufficient lid is actually used, and is secured on for as long as possible throughout the practical in order to ensure no heat escapes, while a material that insulates better than the polystyrene can be used for the cup.
How to lay out the Results Table for this graph
The results table has two main columns, the one on the left is the ‘Volume of NaOH added (cm^3)’, and the other column is the ‘Temperature (°C)’.
The Temperature column has three sub-columns which are for ‘Test 1’, ‘Test 2’, and ‘Average’.
How to lay out the Graph/What does it look like
‘Temperature (°C)’ should be put onto the Y-Axis, while the ‘Volume of NaOH added (cm^3)’ should go onto the X-Axis.
Initially, the points along with the line of best fit should curve up and over, before they then go down and across after the Maximum Temperature Change.
