Homework help (science)

[bottleblond]

My son Ben came home from school with Science homework today but there are 3 questions he doesn't know the answer to. I have googled but can't find anything online. :shrug:

Can anyone help with the following please....

Regarding a syringe..

He has to choose the correct match for each sentence..

1. You can / can't push the plunger far when it has a block of mental in it. This is because the particles in the metal are close together / far apart.

2. When air is in the syringe, the particles are close together / far apart to start with. when you push the plunger, the air particles get closer together / further apart.

3. Kyle and Rebecca were doing an experiment in science, they mixed together 50ml of water and 50ml of alcohol. They found that they ended up with 95ml of mixture. Why is this?

I think i have an idea about the last question but not got a clue about the other two. Any help would be appreciated. Lol eek

xx

[daisycake]

I think the first one is you can't push it far as the particles are close together?

As for the second one I think they are furhter apart to start with but clsoer together when you push it.. seems that if you have air in there it's compressed until you push it right out of the syringe - so the more you push the more together they get until it's released. I could be talking rubbish though!

The last one I don't know though..

Hope that helps, did higher biology in 5th year, might be wrong though :D x

[bottleblond]

Oh DS you are clever

For the last one, i thought the the alcohol starts to dehydrate the water or something along those lines. Science never was me forte pmsl.

Thank you for your help hun

xxxx

[Nigel]

Hi Lisa,
NMP isn’t a free homework service :winks:

Daisycake is right – well done :yesyes:

1. You can / can't push the plunger far when it has a block of mental in it. This is because the particles in the metal are close together / far apart.

Block of mental???

If the particles are already squished tightly together they can't be compressed any further – well not unless you use something with a lot more force than air.

2. When air is in the syringe, the particles are close together / far apart. to start with. when you push the plunger, the air particles get closer together / further apart.

Opposite to the first one.

I’m glad you have an idea for number 3. That sounds more like chemistry, and I opted for physics. Too many bangs and nasty smells coming from the chemistry lab for my liking :ohmy:

Probably something to do with they way they mix?? :shrug:

[bottleblond]

Awww thank you Nigel!

You are both stars. :hugs:

xxx

[lizzie29]

The answer has to do with the different sizes of the water and ethanol molecules. Ethanol molecules are smaller than water molecules, so when the two liquids are mixed together the ethanol falls between the spaces left by the water. It's similar to what happens when you mix a liter of sand and a liter of rocks. You get less than two liters total volume because the sand fell between the rocks, right? Think of miscibility as 'mixability' and it's easy to remember. Fluid volumes (liquids and gases) aren't necessarily additive. Intermolecular forces (hydrogen bonding, London dispersion forces, dipole-dipole forces) also play their part in miscibility, but that's another story.


Sadly I didn't make that up, I found it on the internet!
Hope I understood the question correctly.
http://chemistry.about.com/od/lecturenotesl3/a/miscibility.htm

[evil monkey]

wow cool Lizzie. nice description

everything people have said ^^

also

the last question

i think it is actually 100, but after 50 ml of alcohol you cannnt quite shee the measurrrment dishplay propurly

[bottleblond]

[QUOTE=Nigel;779961]Hi Lisa,
NMP isn’t a free homework service :winks:

I will slip you a fiver when the others ain't looking but this is between you amd me only!!! ;)

[lizzie29]

Er, I'm the only one who answered the third question (although Evil Monkey's answer did make me smile!) so surely that's worth a tenner Lisa?

[diane07]

Lizzie

Lisa has logged out on NMP but i am talking to her and she said you can have a percentage of the tenner :roflmao:

[scaredstiff695]

i like this thread allthough dont really no the questions lol made me smile and forget about anxiety.

hope he gets a good grade now hes got his mummy and mummys friends helping lol xx

used to be caling cheating when i was at school hahah (only kidding)

[SueBee]

The answer is most certianly not density - it has to deal with the size of the molecules and intermolecular forces shared between the molecules. Even though isopropyl alcohol and water arent' the same size (isopropyl is a little bit larger) they do share a critical intermolecular force - hydrogen bonding. This makes it so that when the two molecules come together, they are attracted to one another (as opposed to having no affinity for one another) and thus "pack more closely" to reduce the volume. Unlike you've often learned, volumes ARE NOT additive, to correct a problem like this, scientists usually refer to the partial molar volume of a substance which takes into account interaction with another substance. The same effect can be seen with many other pairs of liquid like water and ethanol or benzene and toluene.

[/B] Eh :shrug: lol

[lizzie29]

What's the percentage Di? Better be more than 50!

[Nigel]

I will slip you a fiver when the others ain't looking but this is between you amd me only!!! ;)


OK, deal :okay:
And for another fiver I’ll pretend I didn’t see that earlier comment :whistles:

Thanks Lizzie :)
I found that interesting, and it wasn’t even my homework!

[lizzie29]

Like I said, I didn't come up with that answer sadly! But I thought it was quite interesting too - good bit of pub quiz knowledge!

Okay, if Nigel is now on a tenner, I want that percentage to be 100% Di - you tell Lisa that!

[Nigel]

Thanks Sue.

That sounds cleverer, but I prefer Lizzie’s answer because I can understand it :wacko:

[lizzie29]

Sue - does yours mean the same as mine?! If you wrote that yourself - blimey, I take my hat off to you!

[SueBee]

LMAO noooooo I didn't write it myself !! Good old google search!

I think it basically means that the molecules of one fit into the spaces of the other, therefore altering the density.

[lizzie29]

Phew! That's what the gist of mine said too.

[SueBee]

LOL lizzie, just read yours - wish my son were here, He's at Uni doing just this subject but I can never guarantee that I'd understand the answer to the question lol

[diane07]

lisa owes alot of money :roflmao:

[lizzie29]

Small price to pay for the education of her child ;) she'll be thanking us when he makes Oxford!

[diane07]

thats true lizzie, charge her £20 :roflmao:

[nomorepanic]

Why can't we have maths questions - I like maths and I know a good froggy that could help out lol

[SueBee]

Maths???? *faints* lol

[bottleblond]

Oh god not maths :wacko: