Effects of surface area

Surface area

Surface area is the amount of exposed surface of a solid substance available for reaction.

Difference between a large and small surface area

Small surface area (powder) = Faster reaction rate

More exposure

Large surface area (like stones) = Slower reaction rate

Less exposure

Explain in terms of collision theory

Increasing the surface area of a solid exposes more particles to collisions. This increases the frequency of collisions per second, leading to more successful collisions, so the reaction rate becomes faster. Reducing surface area slows it down.

Practical for this

Place a fixed mass of marble chips in a conical flask.

Add a HCL

Immediately connect the flask to a gas syringe

Record the volume of CO2 at regular intervals until the reaction stops.

Repeat the experiment with the same mass of marble chips but:

Large chips

Medium chips

Powdered marble

Compare the results and plot graphs.

Independent variable

The surface area of the marble chips

dependent variable

volume of CO₂ gas produced

Mass lost

Control variable

Temperature

Concentration of HCL

CORMMS

C : Keep the mass of marble chips, concentration of HCL

O : nothing

R : Repeat each experiment at least 3 times for each chip size, then calculate a mean.

M : Measure the surface area of marble chips

M : Measure the rate of reaction by recording volume of CO2

S : Use the same observer