Variables inc. Different experiments with different strategies:
Experiment 1: Investigating the rate of dissolving in various temperatures.
Control Variable:
-
The solute is the same: sucrose;C12H22O6(sugar)
-
The solvent is the same: water; H2O
- The mass of sugar is the same: 0.5 g
- The size of the sugar particles is the same: granulated sugar.
- The same quantity of water used: 25ml.
- No stirring or movement for the particles.
Independent Variable
The temperatures are going to differ; this experiment is going to be split up for the various temperatures, therefore each boiling tube has water with different temperatures. In addition, a water bath is going to be used to get a high temperature.
Dependent Variable
Measuring the time, it takes to dissolve the sugar in the water, in minutes.
Experiment 2: Investigating the rate of dissolving with different sizes of sugar particles:
Control Variable:
-
The solute is the same: sucrose;C12H22O6(sugar)
-
The solvent is the same: water; H2O
- The mass of sugar is the same: 0.5 g
- The same quantity of water used: 25ml.
- The same temperature of the water: 70 C
- No stirring or movement for the particles.
- The sugars are going to be in boiling tubes filled with water(77 C), which are going to be in a beaker filled with water with the same temperature, to keep the temperature constant.
Independent Variable:
The sizes of the sugar particles are going to differ, there are four types of sizes of sugar particles used in this experiment: -
Castor sugar, granulated sugar, preserving sugar and coffee sugar.
Dependent Variable:
Same as in Exp. 1.
2. Method
Experiments 1 & 2
(Apparatus diagram on the other page)
I used sucrose/ sugar as my solute for my experiments because:
- It is commonly used.
- Sugar is not harmful.
- I thought of using salt, but sugar is more soluble than salt (NaCl) and I wanted to do the experiment quickly and efficiently, so I used sugar instead. I used sugar for both experiments, so that it could be a fair test.
I used water as my solvent because:
- It can dissolve a wide range of different substances (but there are some exceptions e.g. oil)
- It is also available.
In both experiments, I used a balance to find the mass of the sugar. I thought at first to use a large quantity of sugar, but after my practice experiment I found that it takes a longer time to dissolve without the stirring, so I reduced the mass to 0.5g.
I measured the quantity of water with a measuring cylinder so that I could get an accurate amount of water. The water was then poured into a boiling tube, after this the sugar was poured in. When this happened, I timed how long it took for the sugar to dissolve with a stopwatch.
In experiment 1, I used a water bath to increase the water’s temperature. At first, I thought I could dissolve the sugar at 100 C, but in my practice experiment, I found that steam condenses on the walls of the boiling tube, which blurred my vision, which wasn’t good because I couldn’t see if the sugar dissolved or not. In addition, at 100 C bubbles started to form on the surface of the water, which also stopped me from seeing the sugar to dissolve.
Therefore, I decided to heat the boiling tube at 70 C. I couldn’t keep the temperature of the boiling tube, which had ice cold water, constant because I had no apparatus which could cool the water to the same temperature it started with. Because this boiling tube didn’t have a temperature that was kept constant, I didn’t have the other temperatures constant, otherwise it wouldn’t be a fair test.
In experiment 2, the water’s temperature was 77 C, because in my practice experiment it took a long time for the large sugar particles to dissolve, so I decided to use a high temperature. All four boiling tubes had water in them with the temperature of 77 C and were kept in a beaker filled with water that was also 77 C, so that the temperature was kept constant.
