This is what i wrote:
I have found out that 30cm3 of hydrochloric acid takes the shortest average time for the calcium carbonate to be used up (26.5 seconds), and that 5cm3 of hydrochloric acid takes the longest average time for the calcium carbonate to be used up (222.5 seconds). My graph shows a clear trend: increasing the concentration decreases the time it takes for the calcium carbonate to be used up. This is clearly shown by the strong negative correlation.
Now I know that increasing the concentration of hydrochloric acid increases the rate of reaction because less time means more successful collisions are taking place in a second, therefore equalling an increased rate of reaction. This means that my prediction was right because that is exactly what I predicted.
30cm3 of hydrochloric acid took 26.5 seconds on average for the calcium carbonate to be used up, the fastest out of all the concentrations. This is because there are more acid particles available to hit the calcium carbonate molecules; therefore there is a higher chance of successful collisions and a faster rate of reaction.
25cm3 of hydrochloric acid took 44.5 seconds on average for the calcium carbonate to be used up. This is a slower rate than 30cm3 because there are water particles to get in the way of the hydrochloric acid molecules plus less hydrochloric acid molecules. Therefore there is lesser chance of successful collisions and a slower rate of reaction.
20cm3 of hydrochloric acid took 129.5 seconds on average for the calcium carbonate to be used up. This is slower still.
Get the gist? Anyway it might not help. I hope you get good marks. You've probably finished the coursework already but look at this any way.