Australia's Science Forum

I have a funny feeling strontuim carbonate is insoluble. You could use it and lithium carbonate in there solid form ??!!

yes Rae, you are right, strontium carbonate is insoluble in water. I tried it anyway in the hope that some may soak into the popsticks but it wasnt very exciting. So I have ordered strontium chloride (and lithium chloride). We didnt want to give the kids the solid form of strontium carbonate because they would just make a mess with it.

You may have been able to use the "Dry Powder" method, where you soak a toothpick in distilled water and then use the wet toothpick to pick up a little of the powder. Nothing to dissolve that way.

Ian

Smee, that does sound like fun, I'll try and convince my teachers to do it tomorrow!

Oh Wow! Cool! Totally trying that ASAP.

Revisiting an old topic... Flame tests!!! Aaaarrhhhhggg!!!

For those of you who use the wire loop/wet toothpick/wet paddle pop stick and dry powder methods, how do you keep kids from contaminating the bottles??? I set up some flame kits with little tiny bottles of each sample. Kids use an unfolded paper clip dipped in water and hold it with a wooden peg in the flame. Then they (theoretically) get a new paper clip for the next sample... Nearly all of my little bottles are now contaminated and I've got last minute (well, this morning) notice for a prac exam tomorrow requiring them. I will have to wash them out at get fresh samples. Just wondering if anyone has come up with a fail-safe way of not getting contamination? I like the soft drink bottle idea but I don't know that it would work for prac exam situations if you need a different bunsen for each test to avoid contamination...

Probably wont work for a prace exam but we sit up a different station for each chemical so there is no way they can be contaminated.

When we do the bunsen in a bottle method we use a different station for each chemical. We've also used paddle popsticks soaked and then dried so that crystals of the salt you are using on the sticks.That way the kids don't actually get any chemical bottles.

we use paddle pop sticks soaked in the solutions overnight and then empty the solution out prior to prac. They work better if they are still a bit damp, no bottles for the kids to contaminate.

I am wanting to try doing my flame tests using the method of soaking paddle pop sticks in the solution and letting them dry. Do I use a concentrated solution to soak the sticks.

Get a hard backed razor blade and scrape each side of pop stick as most have a wax coating that stops the solution absorbing
Yes! the more concreated solution the better although when I've done it this way usually grabbed 1M solution off shelf

Science Dimensions 3 has this prac - Firework colours - and the suggested strength for solutions is 0.1M. Soak overnight and don't dry them out. Or if the prac is for after lunch you can soak them first thing in the morning. The paddle pop sticks are placed in the flame straight from the solutions. Like Ocker I usually use the stronger strength solutions for a better colour or stir some extra solid into the solution if it looks too weak. In the end some of them are probably at the point of being saturated. I haven't had a problem getting the paddle pop sticks to absorb the solutions if they are left in long enough.

Lyn.

one school I have heard of burns the solid powder in an evaporating dish with methylated spirits. I have no idea if this is safe - it is an elite public high school.

Sounds like a soon-to-be-extinct school! KA-BOOM!

I use toothpicks. The cheaper the better. Soaked in a conc solution to get the best results. You don't need much for toothpicks, I do it in the little plastic specimen pots. Then the students use tongs to hold the toothpicks in the flame. I don't think you need conc for all solutions but some you do so i just do it for all. The students only get the toothpick not the solution.

a couple of the teachers are complaining that their firework colours aren't spectacular enough. I give them paddle pop sticks that have been soaked overnight in 0.1M soltions and give them the wet sticks. I've found they work if wet and the little darlings don't BURN them. Which is what happened with this class.Another teacher reckons they aren't terrific either, but seing as how the 1st teacher isn't great at supervision, and often has the problem classes, I'm not sure I want them running around with spray bottles or dishes of chemicals (particularly lead salts)

Ocker's set up looks amazing, but not sure if I'd trust all the classes with it. I probably sound paranoid, but his class whacked a rubber bung through the ceiling this morning....don't know if everyone was wearing glasses...

For those using sticks and or spray bottles what concentration? and how do you stop darlings from spraying each other?

Buy the "Dame Edna" glasses from ProfBunsen (less than $2 each) then get all the kids to wear them, turn off the lights and do it as a demo! Take notes between flames, and let them work out the unknowns. Uses less chemicals, but still lots of engagement owing to the fun glasses.

Potassium chloride, strontium chloride, copper chloride, sodium chloride, lithium chloride, calcium chloride, barium chloride were requested for a prac along with an unknown metal chloride. Any suggestions for the unknown that has a colour?