## Water Flow Out of a Burette

Apparatus:

Burette, 2 x 250ml beakers, 100ml measuring cylinder, filter funnel, 2 clamps,

stand & burette clamp, stop clock.

Procedure:

1. Fill the burette with water to about the 0 cm ^{ 3 } mark. Place a beaker below the

nozzle of the burette and then allow the water to flow out of the burette into the beaker.

Notice how the flow rate varies as the burette empties.

A student suggests that the volume flow rate R, of the water (in cm ^{ 3 }/s) is proportional to the volume V, of the water still in the burette.

2. Use the stop clock to determine the time taken t, for the burette to empty when filled to the 0 cm ^{ 3 } mark.

3. Use the measuring cylinder to determine the initial volume V, of water inside the burette when it is filed up to the 0 cm ^{ 3 } mark.

4. Repeat stage 2 for lower levels in the burette down to the 50cm ^{ 3 } mark.

5. Tabulate your results.

6. Draw a graph of initial volume of water, V against time to empty, t. You should obtain a curved line.

7. Select initial volume V = 50cm ^{ 3 }. Draw a tangent to your curve at this point. Measure the gradient of this tangent. This gradient will equal the water flow rate R for this volume.

8. Repeat stage 7 for volumes 40, 30, 20, & 10cm ^{ 3 }.

9. Tabulate your calculations.

10. Plot a suitable graph in order to show whether or not the prediction

made by the student is true.