Main Introduction Initial Observation and Hypothesis Materials and Equipment Experiment Discussion Applications Conclusions
EXPERIMENT We studied the dependence of Current vs. Concentration
in salt solutions. The experiment’s setup picture, taken by a digital camera,
is presented below.
Preparation
1.
Make a holder for
the electrodes consisting of a LEGO part and two metal plates. Attach the plates
to the LEGO part using double-sided scotch tape.
2.
Prepare solutions
with different concentrations of salt in the cells of the container. The
initial amount of the water in each cell is 40 ml.
3.
Weigh the
required amount of salt, add it to the water in cells and stir until the salt
dissolves.
4.
Put the Multimeter in the “Ampermeter” regime and design the following
electrical circuit.
Experimental Procedure
1. Using the battery holder
connect two 1.5-V batteries in parallel, so that the source provides 1.5 V.
2. Put the electrodes into each
cell containing the salt solution of different concentrations and record the
readings of the Multimeter.
3. Record if the bulb lights.
4. Using the battery holder
connect two 1.5-V batteries in series, so that the source provides 3 V.
5. Repeat steps 2 and 3.
Experimental Results
We did the experiment three times. The results of the experiments are
presented in the tables below:
Experimental Series 1
|
n% |
V (V) |
I(mA) |
|
n% |
V (V) |
I(mA) |
|
25 |
1.5 |
10 |
|
25 |
3 |
35 |
|
20 |
1.5 |
8 |
|
20 |
3 |
25 |
|
11 |
1.5 |
7 |
|
11 |
3 |
24 |
|
8 |
1.5 |
6 |
|
8 |
3 |
20 |
|
5 |
1.5 |
5 |
|
5 |
3 |
20 |
|
4 |
1.5 |
4 |
|
4 |
3 |
15 |
|
2 |
1.5 |
3 |
|
2 |
3 |
10 |
Experimental Series 2
|
n% |
V (V) |
I(mA) |
|
n% |
V (V) |
I(mA) |
|
25 |
1.5 |
12 |
|
25 |
3 |
30 |
|
20 |
1.5 |
11 |
|
20 |
3 |
27 |
|
11 |
1.5 |
10 |
|
11 |
3 |
25 |
|
8 |
1.5 |
9 |
|
8 |
3 |
22 |
|
5 |
1.5 |
8 |
|
5 |
3 |
18 |
|
4 |
1.5 |
7 |
|
4 |
3 |
14 |
|
2 |
1.5 |
3 |
|
2 |
3 |
10 |
Experimental Series 3
|
n% |
V (V) |
I(mA) |
|
n% |
V (V) |
I(mA) |
|
25 |
1.5 |
11 |
|
25 |
3 |
32 |
|
20 |
1.5 |
10 |
|
20 |
3 |
31 |
|
11 |
1.5 |
9 |
|
11 |
3 |
25 |
|
8 |
1.5 |
8 |
|
8 |
3 |
21 |
|
5 |
1.5 |
6 |
|
5 |
3 |
18 |
|
4 |
1.5 |
5 |
|
4 |
3 |
13 |
|
2 |
1.5 |
4 |
|
2 |
3 |
12 |
Observations
During the experiments we also
observed if the bulb lit. At 1.5 V the bulb never lit. For 3
V the bulb lit for concentrations of 4% and higher.
We also observed that it was difficult
to make homogenous salt solutions with concentrations higher then 30% in cold
water. It would be possible if we heated the water. However this was outside of
our goals.
In each experiment we observed that
the solution turned yellow and it fizzed.