Australia's Science Forum

Hi everyone
We are doing rocket experiments starting today. They will be doing variations of the "rocket" chemistry. One variation is using mentos and coke. I have tried this before and found it not to work. Quikeze worked a little better. Do you have to scrape the sides of the mentos for the reaction to start? Another is the vinegar and bi-carb. Also an alka seltzer in water. We are hoping to do the larger soda bottle launched on a broom handle after the smaller experiments. Does anyone have any tips or other suggestions for this topic please?
Rita

I think you need to use DIET coke, it does not work with normal coke, and I think it has to be the spearmint or mint mentos not the fruity ones... Why I cannot remember at this moment, but when I do I will write back. And you do not need to scrape the sides, just plunk it in! We did this exp last week and it got up to 2m, it was great and the students loved it!!!

Hi all,
I thought the Mentos had to be the US variety. Apparently, they are more 'dimply' (more surface area) than the Oz ones. We have used Alka Seltzer and water in film cannisters, and it works well.
Ellice.

We have had great success with the DIET coke and mentos (in the blue packet, no, the fruit ones dont work). We do two demonstrations.
1. Cold diet coke and room temperature mentos (as they would normally be consumed). Put the mentos in a test tube, cover with a piece of glass like the ones used with gas jars, invert over the diet coke and remove the glass, allowing the mentos to fall in the bottle. This demonstration usually results in a small geyser ( a couple of centimeters) and is quite boring. However, Demonstration 2 will impress!
2. This time warm the diet coke in a bucket of hot water for an hour. Carefully remove lid off bottle and doing the same as demo 1 but this time use mentos that have been frozen overnight. The reaction is quite stunning with a fountain of coke shooting 3m into the air. Make sure the person who is doing it has safety glasses and something to protect their clothes, we ask the students to be a volunteer and sometimes they dont move out the way quick enough and get covered with it.
As well as being great fun it also shows how temperature can affect the rate of reactions.
Cheers
Jen

Hi All,

This is not directly related to the "Rocket Experiment" but this Saturday coming I am coming back to school to Launch some rockets of mine on the oval.

I use the solid rocket fuel in them and have launched quite a few of them just of late. The problem that I always face is the wind but hopefully this Saturday coming I can get out and send them back up.

The family love it and my 4 year old gets involved by pushing the launch button..

Nothing better than the solid rocket fuel....

Cheers,

Robb.....

G'day Robb! Can I come and watch? I'd love to see these being launched! Put the old water rocket into perspective!!!!

Hi Richard,

I will give a phone call in a couple of minutes so stand by...

Cheers,

Robb.....

We have done the Mentos Exp as follows
1.) drill a small hole in the lid of a Diet Coke bottle (the photo shows 5 holes, but 1 should be sufficient)
2.) drill holes through 5 Mentos
3.) thread the 5 mentos onto a piece of string
4.) thread the ends of the string through the hole in the lid, and tie so that it does not fall through, but keeps mentos out of the Coke
5.) screw the lid on tightly to the bottle
6.) cut the string, allowing the mentos to fall into the Diet Coke
7.) stand back!

regards
Ian

Yes, thats exactly how we do it, too Ian.

You should all check out this film clip on the coke and mentos exp, from youtube, its brilliant!


http://www.youtube.com/watch?v=hKoB0MHVBvM

We use the Estes solid rocket engines glue-gunned into a thin cardboard tube with wadding and recovery system (parachute made from cotton and plastic sheet) attached to nose cone (sanded-down balsa block) with a thumb-tack which is in turn attached to the tube with rubber bands linked togeteher. Balsa fins glue-gunned to sides of tube.

Hi everyone
Thanks for your help. You have given me some great ideas.
The class yesterday tried the mentos in coke anyway. Nothing happened. Tried the quikeze and coke. Little fizz. Tried vinegar and bicarb. Reacted too quickly or students too slow, but still got the idea. Tried alka seltzer and water. All were impressed. The teacher was pleased with the order that the experiments were put in practice because the best one was the last one. Only 5 more classes to go!
Thanks again
Rita

Hi Rita,
I really urge you to try the coke and mentos again.
just make sure you use really WARM DIET coke and FROZEN mentos.
I freeze the mentos overnight and warm the diet coke up in a bucket of hot water for a couple of hours.
Drop all the mentos in the bottle in one go, see earlier posting for more details.
Cheers
Jen

Mythbusters really went to town investigating this one. They did all the fair testing you could ask for, and the conclusion was that it is the aspartame in Diet Coke, combined with the preservatives AND caffeine that makes the fountain work best. The blue Mentos are the only ones to use, although we have had really good results with a test tube full of salt. The peppermint mentos have a pitted surface which helps to catalyse all the CO2 out of the Diet Coke at once. I've also found that the "2 litres Diet Coke to 1 packet of Mentos" to be a formula that doesn't like to be scaled down - i.e. don't try it with little bottles and less Mentos. Might be something to do with the quantity of CO2 trying to escape at once.

Cheers, K

Hi
Had my 14 year old son help me with diet coke in hot water and the mentos in freezer out in the backyard. He was quite excited to help.
We put the diet coke in hot water. My son raced back to me not long after, worried that the bottle would explode as the bottle became very hot and the bottle looked fatter. He didn't want to leave it in the hot water any longer. So we did the experiment. He loved it. The geyser went about 4-5 foot. Is it the longer you leave the diet coke in the hot water the greater the height? It looks like we'll be making more rockets during the holidays to show off to the cousins!!

Cheers
Rita

Glad you had another go at it Rita. yes the warmer the coke, the heigher the fountain. We usually get 12 feet high. Just be careful when opening the hot diet coke, do it slowly so all the fizz doesn't coming rushing out.

Hi All,

Unfortunately the weather was against us again which prevented any launching of the model Rockets from the school oval.

I guess it is a arduous task trying to pick a launch window that suits the weather, but as everyone knows, these controls are beyond any scope...

I will try to include some photos of the next launch(s) and give you a better perspective of the day.

Cheers,

Robb.....

This sounds like so much fun, (the diet coke and mentos) but I am not quite sure how it relates to rockets, since nothing is actually 'launched'... Is it used as an example of how fuel is blasted out? A junior school teacher has asked if I have any exciting science things to do with space. We did the bicarb soda and vinegar film canister rockets last year with the same class, so I was hoping to come up with something different. Any ideas?

You could do water rockets using a soft drink bottle, Ice cream container or lid as fins, water and a bike pump. I know one of the teachers who no longer works here, had his class in 2006 make rockets out of cardboard and they used a solid fuel rocket engine, not sure if you could do this in other states or even in Tassie anymore.

Hi all,

We did rockets at a school assembly last year. We had several brands of diet soft drinks and mentos, sand, brick and dry clay. The dry clay by far was the best reaction and was quite spectacular.

What did you do with the Dry Clay etc?