Electrolyte Challenge

[deleted-85131]

Wow! This experiment discouraged me from ever having my kids do an experiment again. First the instructions about the multimeter and setup are so complicated. We ruined our first when the coils touch. So almost $100 later, we have the following data and are confused on how to put it in the G=I/V formula. Please help us! Our readings were: OJ 101.6, Distilled Water 0, Gatorade 50.3 and Smart Water 25.0. What is the unit is that microamps. I have read the radioshack manual twelve times. I have googled it and can't figure out. I think the multimeter was set on 200 Micro Amps but ours was automatic so I am lost. Does my son just take the above numbers and divide by 9 the volts of the battery to determine G. If so, what unit of measurement is G labeled as? Please help we are so lpst.

[rmarz]

momofkyle - Sorry you are having difficulties. From your measured data it looks like you are getting the proper results. I think you are experiencing difficulties interpreting measurements with the autoranging multimeter. I'm not familiar with this model, but it seems with an autoranging feature you should be shown what the units are in the display or on some LED that tells you that the numbers represent microamps, milliamps etc. I believe you are measuring milliamps based on an observation I made several years ago with this experiment where I just tested distilled water and OJ. My OJ reading was around 60-70 milliamps (compared to your 101.6 reading). I would have thought that your Gatorade would have been higher reading than the OJ, but that is what the scientific method is all about. Replacing intuition and bias with real, demonstrable data.

The calculation of conductivity, using the formula G=I/V is appropriate. The unit is called a 'Siemen'. In the old days, because conductivity was thought of as the reciprocal of Resistance (measured in ohms), conductivity was measured as 1/R and the unit expressed as the 'mho' (or ohm spelled backwards). Ignore this, it is just a historical note.

It is important that when using the formula G=I/V, your units have to be expressed as whole units of voltage and current, Volts and Amperes. In your measurements, assume that the voltage is 9 volts (using a 9 volt battery), but the currents will be - 101.6 ma = 0.1016 amperes. 50.6 ma = 0.0506 amperes, and 25 ma = 0.025 amperes. These should give you the proper conductivity units in Siemens.

Rick Marz

[Alee2913]

hi, i am a student currently doing the experiment "electrolyte challenge" only i have changed the solutions instead of OJ i have decided to use powerade, vitamin water, monster and coke only i am having trouble with the readings from the multimeter. i have googled it a million times and tried to read the procedure listed but well i have a few questions on what i should do to get the proper data. frist, what happens to the red lead? i plugged in the black one into the COM jack and i set the range selector to 10A as well, but what am i supposed to do with the red lead?? the instructions are not very clear on that. what i decided to do was connect it to the battery clip as this is what looks most like the image on firgure 2 which by the way does not correspond with the procedure. my other problem is that once i took the measurements down i got things like .04 for the Gatorade (i dont even know what im measuring) .01 for the Vitamin water, .02 for the monster, .01 for the coke, o.o for the distilled water and , .02 for the tap water. i have done this more 5 times various different ways and the results still dont correspond with each other. also, the measurements keep changing so please help!! i need to turn this in in a few days so please respond ASAP!

[rmarz]

Alee2913 - The multimeter is set to a current measurement range and is in series with the battery and liquid being tested. The RED lead should be at the battery positive (+). The black lead is connected to the liquid electrode. The other liquid electrode is attached to the battery negative (-). One of the problems may be using too high of a range on your multimeter. On the 10 amp full scale setting, you are trying to measure milliamps of current. The way the digital meter is rounding off as well as meter sensitivity issues of measuring low levels of current on a high range scale may be creating problems. Try something like the 200 milliamp range or close to it. You might find more repeatable measurements that way. The range of currents observed in this experiment range from near zero (or microamps) for distilled water up to 100 milliamps or so for highly ionized solutions.

Rick Marz

[Alee2913]

Rick Marz, thank you very much but where do you suggest i turn the range selector to? im a little unsure as to put it to 200m on DCV or on the DCA ?! and what does the wierd symbol (not the m) on the DCA stand for?

[rmarz]

Alee2913 - The term DCV refers to DC Volts or voltage. The term DCA refers to DC Amps or DC current. I'm not familiar with the model of multimeter you are using, but you want to be in a DCA, or current range, of approximately 500 milliamps or less, preferably 200 milliamps. These equate to a fraction of an ampere, in these cases, 0.5 or 0.2 amps, DC. If you are still having problems, look up the reference on using multimeters at this Science Buddies location, and if that doesn't solve your question send along the model number and brand of the multimeter you are using and I'll see if I can locate a reference on the web and help you with the connections.

https://www.sciencebuddies.org/science- ... eter.shtml

Rick Marz

[starwars]

we r doing the electrolyte challenge and got one set of readings, then half way thru second the meter quit reading. we have 4 meters, have replaced the copper wire and battery, diconnected everything and reconnected. We have 5 days to finish and can not get any more readings what do you suggest we try????? Help!!!

[rmarz]

starwars - Do you mean you have tried 4 different multimeters and none of them are showing any readings? Check your setup again and multimeter range settings for something like 200 millamps DC current. Check the condition of your 9 Volt battery with one of the multimeters in the appropriate DC voltage range. It's also possible that a protective fuse has blown in a multimeter. If the battery voltage check gives you a good reading, check the appropriate milliameter range (possibly 200 milliamps DC) using a 1K (1000 ohm) resistor in series with the 9 Volt battery and multimeter. Using the equation I=E/R, (I in amperes = 9/1000) you should get a reading of about 0.009 amperes or 9 milliamps. Use any resistor above 100 ohms that you might have with this equation to do a test. Check to see if the measured current is close to the calculated current. Refresh yourself with the primer on multimeter use linked below.

https://www.sciencebuddies.org/science- ... eter.shtml

Rick Marz

[Alee2913]

Rick Marz, thanks again, and yes i tried it again, i went to the link you sent me, and of the picture of multimeters that it has, i have the model on the left hand side, the smallest, yellow one. where should i set it too there? and i tried setting it on 200 DCA, but all my readings ended up in the 0.2's and 0.5's they werent very varied. ok and even if i am on the right track, from then, how would i figure out how many electrons, or even the current of each drink?

[rmarz]

Alee2913 - Just to make sure your connections are correct. The black lead of the multimeter is inserted into the COM or (-) jack. The red lead is inserted into the jacket marked 'V Ω mA' or similar. Be sure it isn't in the special 10A jack. The range should be set in the DCA area, and set to 200m (200 milliamps). The other current ranges on the meter are 200µ (200 microamps), 2000µ (or 2 milliamps) and 20m (20 milliamps). With the higher ionized liquids, you should read numbers between 50-200 milliamps. With distilled water it should be a very low number and may have to be read with the 200µ range. Make sure your battery is still fresh and reading 9 volts (or slightly higher) with no load, using the multimeter in the 20 VDC range. You should definitely see varying readings with the different liquids. To test the current measuring try to use the 9 volt battery in series with the multimeter and a 1000 Ω resistor. Your reading should be about 9 milliamps. The Science Buddies experiment page shows how to calculate conductance from your readings.

Rick Marz

[popsicleluver]

Hi! I am doing the "electrolyte challenge" using orange juice, pickle juice, gatorade, and water (1/2cup). I have completed my experiment and am now analyzing the data, but all of my numbers that i recorded off of the multimeter were negative...? Should I just ignore the negative sign? These are my numbers:
Water: -0.6 Orange Juice: -34.9 Pickle Juice: -74.9 Gatorade: -77.7
I also don't know if my multimeter was measuring in milliamps or microamps...? I had it set under the direct current setting at the 200m. I have tried dividing by both 1,000,000 and 1,000 and my answers are coming out in scientific notation with negative exponents. Should I leave it in scientific notation and THEN divide by 9-Volts? And should I leave it in scientific notation when I graph it and put it in my tables too? All suggestions will be appreciated!! Thank You!!

[rmarz]

popsicleluver - I think you are seeing correct results. The red lead of the multimeter should be connected toward the positive (+) battery terminal. In any case, ignore the negative sign. Your data looks plausible. If you are reading 0.6 on the 200 milliamp scale for water you are reading 0.6 milliamps or 600 microamps. This seems like tap water that contains a lot of minerals or salts. Distilled water should give you a much lower result. The other values seem appropriate for the other liquids. I recall doing this as a simple test on orange juice and getting something in the neighborhood of 70 milliamps. Your reading of 34.9 might just be a variant of juice or an indication that your battery is weak. If you have access to another multimeter, measure the actual battery voltage while under load to see what the terminal voltage really is. Use that measured value for your conductance calculations. A small 9 volt battery will run down fairly quickly when under loads approaching 100 milliamps. Some references give the capacity of a small 9 volt battery of about 500 milliamp-hours. This capacity assumes a much lower rate of drain more in the 20 milliamp rate or lower. I would leave my graph in whole numbers with an appropriate scale legend. Putting the data in scientific notation works well when showing data over several magnitudes or when data that has an inherent logarithmic character.

Rick Marz

[aishwarya_meshram]

plss help..i did this project with the multimeter set to ac ..cause when i set it on dc it showed no readings at all.. just a zero .. so now m with my readings as follows tap waer-19 distilled water-18 orange juice-19.3 lemon juice-19.7 and sports drink-19.1 ..i also dont know the unit ...plss help ...i have to submit it day after tomorrow.. and i cant do my experiment again ...pls can u help me with something?

[rmarz]

aishwarya_meshram - The procedure for this experiment is to measure DC current through the liquid being tested using a multimeter and 9 volt battery in a series circuit. This measurement is usually measured in units of 10's of milliamps DC current. Multimeters are not capable of measuring AC current (there are sophisticated instruments to do that, but a common multimeter is not one) so I don't know what range your meter was set to. The only AC ranges on simple multimeters are voltage ranges, usually 0-200 and 0-750 volts AC. I don't know what values you are measuring. It is possible that your meter is damaged or a fuse inside the meter is blown. If you have access to a resistor between 1000 and 10000 ohms, try to measure current through it using a DC current range of 0-20 mADC in series with the 9 volt battery, just like the circuit you have been using (replacing the sensing coils with the resistor). If you get no reading, and your battery is good, the meter is not working.

Rick Marz

[deleted-306595]

I am a student. Just wondering: Do you need to buy the alligator clips that are already attached to insulated wire? Or can you just only use bare copper wire and attach two alligator clip clamps? Also, will 18 gauge copper wire work for the experiment instead of 24 gauge? Please reply ASAP.

[norman40]

Hello vikramn,

I’m assuming that you are working on the project described here:

https://www.sciencebuddies.org/science- ... p053.shtml

The insulated wires with alligator clips make it easy to assemble the circuit shown in the project description. You could build the circuit without using alligator clips if you’d rather do it that way. Just twist wire ends (with insulation stripped away) together where you would have used clips. My suggestion is to use insulated wire everywhere except for the conductance sensor. That way you will avoid a short circuit resulting from wires accidentally touching.

The conductance sensor must have bare wire to work. The 24 gauge wire will be easier to wrap around the drinking straw than thicker 18 gauge wire.

I hope this helps. Please post again if you have more questions.

A. Norman

[deleted-306595]

Ok! Thanks!

[deleted-306595]

Also...
Can you use the alligator clips to connect the conductance sensor to the battery clip wire?
Can you use 18 gauge copper wire as the wiring to your circuit?
How do you connect alligator clips to 18 gauge copper wire?

[norman40]

Hi vikramn,

Yes, you could use alligator clips to connect the conductance sensor to the wire from the battery. You could twist the two wires together and clamp them with an alligator clip. Or you could attach an alligator clip to the battery wire then clip onto the conductance sesnor wire.

The 18 gauge copper should work fine for your circuit. I think alligator clips can be crimped on to your wire. You might need a crimping tool to do this.

I hope this helps. Please post again if you have more questions.

A. Norman

[deleted-306595]

Can you measure the conductance of distilled water using the 200mA setting on the multimeter?
My multimeter doesn't have the 200 microamps setting. Is that ok? Also, can you use 18 gauge wire for both the circuit and the conductance sensor, or will this cause a short circuit?

[rmarz]

vikramm - Unfortunately, the conductance of distilled water is so low, that the expected readings you will get will likely be in microamps. A 200 mADC range will not be able to measure current that low. Perhaps you could borrow a suitable meter to finish your experiment.

The use of 18 gauge wire is not a problem. The only concern in this experiment is that the two coils of wire in your sensor not touch each other. You should be fine with 18 gauge.

Rick Marz