Science Buddies: "Ask an Expert"

Hi, I am doing a project on 3 different 9 volt batteries, Energizer, Duracell and Radioshack with a motor attached so I can check the voltage meter every hour. The Energizer and duacell battery was $4.79 and the radioshack was $4.99.
My problemis that I don't know how to word my hypothisis.
I want to guess that energizer will win becasue it is an exensive battery and I also like their advertizing claim that "the battery keeps going and going" But all the batteries are in the same price range.
Help, I have been doing my experiment and I need to learn how to write a proper hypothisis.
Thanks

ari,

I order to help you word your hypothesis, I need to first know the question you are trying to answer. It looks to me that you are trying to figure out which battery will produce the most voltage per hour. Is this correct?

If this is correct, then I would suggest wording your hypothesis something like this: "I think that the ____________ battery will produce the most voltage per hour because ________________." (fill in the blanks with your ideas and opinions).

If this is not what your question is, try to explain to me your question so that I can help you.

Yes, something to that effect. I am trying to figure out which battery will last the longest and at the same time I am taking voltage readings every hour. Tell me if you think this is good.

I think that the energizer battery will last the longest. I have researched this on the internet and in it's test's it is proved to have more batteries than any other manufaturer and also lasts the longest. Also, I like their advertising claim that "the bunny keep going and going"!!

i never thought of your idea though. i was not even considering having the voltage in my hypothisis, Just which battery would last the longest. I was doing the voltage meter becasue it is more accurate in telling me when the battery is dead.

Please help me and tell me what you think. I am so bad at this. Then I will use the voltage readings in a display. Thanks for helping me

ari,

You're not bad at this, your just getting started. Practice makes perfect!

So, you are basically trying to answer the question"Which battery lasts the longest?" by measuring the number of volts the battery produces. Is this correct?

If this is what you are intending to do, then you need to figure out at what point you are going to call a battery "dead." Is it when the battery puts out less than 1 volt? When it puts out less than .5 volts? 5 volts? It doesn't matter so much which number you pick as it does that you use the same number for every single battery.

So, this is how you worded your hypothesis (I'm using your words here): I want to guess that energizer will win becasue it is an expensive battery and I also like their advertizing claim that "the battery keeps going and going. I have researched this on the internet"

I might change your hypothesis to say: "I think that the Energizer battey will last the longest because the research I have done on the internet says so, the Energizer brand is expensive, and the advertisements say 'It keeps on going and going.' "

Thanks for your help. I am thinking that the battery is dead when the motor stops and it usually stop's at about 2 volts. I'm just getting myself sick overth is. i should have done something else!! Anyway, I will then make a graph on excel with al the hours and figure something out.
Thanks again.
Oh, The energizer brand is the same amount of money as the duracell brand so in my hypothesis I liked the way you worded it but they will also know that the duracell is the same amount of money. On the internet it did say that it is the most expensive brand, so how can I wod it differrently? Any more help with the wording would be appreciated.
thanks
Ari

ari,

As a side-note, there are many factors that go into the marketing elements you've been considering:

- price: market leaders can command higher prices, but may have higher advertising expense. Here, prices are not significantly different.
prices are set as part of the overall marketing champaign for the the product.

-slogans: generally have to be true at some level, or others can challenge them in court - the question how untrue and can a challenge be proved
slogans are set as part of the overall marketing champaign for the the product.

i AM SO SORRY TO BOTHER YOU AGAIN. i HAVE DECIDED TO GO WITH JUST THE DURACELL AND ENERGIZER BATTERY. ON MY SECONd TEST WITH DURACELL IT DID NOT LAST AS LONG AS THE FIST ONE.
ANYWAY, help me with my hypothisis!!! What should I say now?
Give me an idea. i am so bad at wording it. They are both the same exact amount of money so how can I say that I think energizer will do better, even though this is what they say on the internet.
Help me and I won't bother you anymore. Keep in mind that we are only doing duracell and energizer the two top batteries.
thanks
Ari

Ari:

Your hypothesis is supposed to be posed before you do your experiment. It's no fair doing an experiment first, then altering your hypothesis so you are perfectly right. In fact, very much of the real developments in science occur when hypotheses are proven WRONG. If we knew the answers to everything, why have to do experiments.

As David has said, using prices for comparisons are difficult. What if you had gotten the Energizer on sale, but didn't catch the Duracell on sale. Just changing the price of the battery doesn't make it last longer or shorter. It lasts as long as what it was designed for, minus any variations that occur in using it in the real world.

There are many endpoints that you can use for when the battery is dead. You can pick an arbitrary voltage, and consider the battery dead when its voltage drops below that point. You can have the battery do work (such as turning a motor), and when that work stops, the battery is considered dead. You can have the battery light a bulb. When the bulb cannot be seen as being lit, the battery is considered dead. There are many, many more possibilities. You seem to have chosen putting a load on the battery (motor) and considering it dead when it drops below a certain voltage.

Different types of batteries have different discharge curves. So the point at which its voltage goes below is an important one when you choose it. Do some research on the internet on discharge curves and batteries.

Here's one example. Do a google search on "9V Battery Discharge Curve", for example, and you will find some.


As you can see, you can pick any voltage below when the graphs drop straight down, and this would be an appropriate voltage to use to call the battery dead. Doesn't matter which you pick. You could also pick a voltage when all the graphs are still sloping down gradually, but it will be very difficult to tell the difference between batteries if you use that point. So 4V, or 3 V, for example, would work equally well.

ari,

Like zzzdoc said, you need to make your hypothesis BEFORE you do any experiments. So you need to stick with your original one which was:

"I think that the Energizer battey will last the longest because the research I have done on the internet says so, the Energizer brand is expensive, and the advertisements say 'It keeps on going and going.' "

If you want to get rid of the part about cost, you could just say:

"I think that the Energizer battey will last the longest because the research I have done on the internet says so and the advertisements say 'It keeps on going and going.' "

advertisements say "It keeps on going and going."

As I mentioned earlier, statements in company provided advertising have their issues. It's best to stick with independent (or at least audited) data.

Duracell, also, makes a longevity claim, with it's product name. (As I mentioned earlier, product naming is a key part of product marketing.)

With pricing, advertising and naming gone that leaves your internet research as the main input (as long as it's independent data!).