If you stir sugar that is in water, it seems to disappear. But the object is still in the water, because if you were to drink it you can still taste the sweetness of the sugar in it. Like in a cup of tea for example. You can explain why this happens by using The Kinetic Theory. The Kinetic Theory The Kinetic theory is the theory that matter is made up of loads of tiny little particles that always move around. This is because all types of matter are made up of little invisible particles which are atoms, molecules and ions.
Because all particles move around all the time it means they have to move, but if you freeze the molecules they slow down and if you heat them up they move faster. Heavier particles will move slower than lighter particles in different heats. When a solid dissolves it looks like it has disappeared because its particles get spread in between the water particles. Prediction I predict that the sugar cube will dissolve because there will be movement and the faster the particles move the faster the sugar cubes will dissolve because there is more movement. Diagram
Apparatus Magnetic stirrer, sugar cube, beaker, stopwatch, scales Planning I am going to use a magnetic stirrer to stir the sugar cubes in the water for me. I am going to set it on settings 2, 4, 6, 8, & 10 speeds and see how long it takes for the sugar cubes to dissolve using this so the stirring is even and accurate as a person wouldn’t be able to stir it evenly. I am also going to weigh all of the sugar cubes and see how heavy they were. Method Step 1:measure out 200 ml of water and put it into a beaker Step 2:weigh the sugar cube and record the weight
Step 3:put sugar cube into beaker and start stopwatch Step 4:record the time taken for sugar cube to dissolve Step 5:restart the experiment from step 1 and do it 36 times Safety There wasn’t a lot really dangerous about the experiment we did as we did it with a magnetic stirrer so we didn’t really need to worry about safety that much. My predictions were right as the sugar cubes did dissolve quicker the faster they got stirred but there was a strange result in the third experiment which went slower but that could have been because only one of our sugar cubes was the average size.
It was supposed to be which was 75 grams so this may have affected the experiment but the other 5 results do work properly and dissolve faster the faster they are stirred. Fair Test I made my test fair by filling all of the beakers to 200 ml of water and adding the sugar cubes at the same time as we started the sugar cube and by keeping the speeds of the stirrer the same all the way through the tests.
What we changed were the speeds for the different experiments and changed them and used the following speeds 0, 2, 4, 6, 8 ; 10 and did three of each experiment to try and get rid of any strange results but we still got one. Errors I think the points that could have made the experiment wrong were the speed at which we started and stopped the stopwatch for each experiment. Also there could have been a slight difference in the amount of water in the beakers. The way it was stirred couldn’t have been wrong because it was done using a magnetic stirrer.
I think the third lot of experiments were faulty or one of them was because we got an abnormal result which said the time taken to dissolve got slower when the sped got faster which was wrong as all the rest of the results follow this pattern. We could improve this result by doing that part again to see if they come out the same. The other thing which could have caused errors was the size of the sugar cubes as they were supposed to be 75 g. Only one of ours was that weight so that could have messed our experiment up. If I did it again I would make them all the same weight.