Main Introduction Initial Observation and Hypothesis Materials and Equipment Experiment Discussion Applications Conclusions

INITIAL OBSERVATION

We’ve learned at school that water is a conductor but its conductivity is very low. This can be observed by hooking it up to a light bulb (the bulb does not light). Adding salt increases the conductivity and the bulb lights.

To find out how electrical current depends on the concentration of salt in the solution we designed a simple electrical circuit consisting of one or two 1.5-V batteries, a bulb and electrodes; the electrodes were placed in the container of water. We were able to create 1.5 and 3-V sources respectively by connecting the batteries in parallel and in series.

We observed that in the pure water the bulb didn’t light for both 1.5 and 3-V volts. Then we started adding salt to the water and stirred it to prepare a salty solution. At some concentration of salt the bulb lit. As we added more salt the bulb lit brighter.

At a concentration of salt greater than 30% the salt no longer completely dissolved.

Through the initial experiment we found out that 1.5-V voltage was not enough to light the bulb.

HYPOTHESIS

Since the brightness of the light depends on the current passing through the bulb we suggested that

1. Adding salt to the water increases the conductivity of the solution.

2. Increase of concentration of salt in the solution leads to an increase of the current through the circuit, and eventually the bulb lights brighter.