Prediction:
I predict that when the amount of ammonium chloride is increased, the temperature will decrease at a proportional rate to when mass is added which will produce a graph like this,
This shows that mass and temperature in an endothermic reaction are proportional as the line of best fit goes through the origin and the line is straight. This is because the more mass added results in more energy needed to break up the giant lattice, resulting in temperature fall. An example of showing that my prediction is correct and that the two are proportional to each other is to say that when the mass of ammonium chloride is 2g it will produce a decrease in temperature of 4 degrees Celsius. So therefore when the mass is doubled so will the temperature decrease, as there is merle just double the amount of mass which means that it will take double the amount of energy to break down the lattice, resulting in doubling the temperature decrease.
Variable:
The variable in the experiment will be the mass of the ammonium chloride, which I will be putting random amounts of in to the water so that I obtain good results to make a graph. The volume of the water in which the ammonium chloride will react with will remain constant at all times (50ml). We will be doing the experiment in a classroom so the temperature should not change and will remain constant so that heat doesn’t affect the experiment. The same amount of stirs of the solution will be applied to each test, each time so that we help each reaction the same, in helping the break up of the lattice, so that it is fair. The thermometer each time will be left in the water before the ammonium chloride is added for a few minutes to make sure it is at the correct temperature.
Fair test:
To make this a fair test we will use electronic weighing machines to weight out the ammonium chloride so that the mass is recorded properly and is correct to 2 decimal places. The volume of water will stay the same as concentration of the water may affect the experiment this also applying to the amount of stirs, as it could affect the experiment and give anomalous results. We will also carry out each test for each mass three times so that we get an average temperature decrease and can eliminate any anomalous results easily.
We will also contain the experiments in a polystyrene cup as it is an insulator so temperature from the surroundings or heat from people’s hands will not be transferred to the solution, which will cause inaccurate results.
Safety:
Ammonium chloride is a chemical that can cause serious damage to eyes, so therefore goggles must be worn at all times to protect the eyes. Also if you spill some of the ammonium chloride on your skin make sure to wash it off straight away in case in penetrates in to your skin through cuts etc.
Equipment:
A measuring cylinder, to measure out the amount of distilled water to be used in the experiment.
An electronic weighting machine, this is to be used to accurately measure the mass of the ammonium chloride.
A stirring rod, to stir the solution.
Polystyrene cup, to contain the solution and act as an insulator.
A glass beaker, to hold the polystyrene cup securely.
A thermometer, to measure the temperature before and after the reaction.
A spatula, to obtain the ammonium chloride from its container on to the scales.
Ammonium chloride.
Diagram:
Method:
- Set up apparatus as shown.
- Now measure out 50ml cubed of distilled water and pour it in the polystyrene cup.
- Now measure the temperature of the water, and record it.
- Now weight out different amounts of ammonium chloride starting with little and then more.
- Now record the mass of the ammonium chloride and tip it in to the polystyrene cup and stir with the stirring rod.
- You keep stirring for 1 or 2 minutes and watch for the lowest temperature the thermometer gets to and record that result.
- Do this for each mass 3 times and work out an average temperature change.
- Do 2-7 for at least 6 different masses and display them in a table like this,
why p[aln is good
Graph:
Analysis:
Evaluation:
