6.2: Collision (2)

6.2.4 –Predict and explain, using the collision theory, the qualitative effects of particle size, temperature, concentration and pressure on the rate of a reaction.

1.      What was the independent variable?

The surface area of the marble chips

2.      What was the dependent variable?

The time it takes for the marble chips to react in order to produce 100cm³ of carbon dioxide
3.      What variables were controlled?

The temperature of the room remained the same, the volume of acid used (50cm³) and the mass of the calcium carbonate (around 6.1 grams)
4.      Using collision theory, explain the following the shape of graphs at the start of the reaction.

The shape of the graphs shows that the reaction is an increasing slope.

5.      What does the gradient of the graph at any one point represent?

The gradient shows the volume of carbon dioxide produced over time in seconds.
6.      What are the units for the gradient of the graph?

The unit is cm³ over seconds.
7.      Discuss the reasons for the differences in the shape of the graphs.

The graph shows that the rate of reaction for the marble chip (in powder form) increases since the surface area is more. So the more surface area there is, the higher chances for the particles to collide. It also shows how the smallest-sized chips reacts the slowest. The slow rate of reaction is followed by the medium-sized chips and the large-sized chips. However, it appears the rate of reaction for small-sized chips is faster than the rest.  Decreasing the size of the particle increases the rate of reaction since it has more surface area. There could be some error since it could be that the number of marble chips are not the same in order to keep the mass the same.