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Topic: A rock  (Read 13591 times)

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Offline Lodve

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A rock
« on: August 23, 2010, 03:53:40 PM »
A rock is placed on a balance and its mass is determined as 12.1 g. When the rock is then placd in a graduated culynder that originally contains 11.3 mL og water, the new volum is roughly 17 mL. How should the density of the rock be reported?

This task doesn't seem hard at all for those who have had chemistry, but I don't know why I can't solve it. I'm relatively new here, so don't get irritated if I post easily tasks. I've never had chemistry before, so it's kinda new for me :P

Offline Borek

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Re: A rock
« Reply #1 on: August 23, 2010, 03:56:16 PM »
What is definition of density?
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Offline Lodve

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Re: A rock
« Reply #2 on: August 23, 2010, 04:25:03 PM »
mass divided to volum?

Offline Borek

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Re: A rock
« Reply #3 on: August 23, 2010, 04:45:11 PM »
Good. Can you calculate mass and volume from a given data?
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Offline Lodve

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Re: A rock
« Reply #4 on: August 23, 2010, 04:51:49 PM »
Ahhh, you just divide 12.1g to 17mL which will give 0.711g/ml?
You know, I don't have the answer to this question :P

Offline DrCMS

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Re: A rock
« Reply #5 on: August 23, 2010, 04:55:55 PM »
Ahhh, you just divide 12.1g to 17mL which will give 0.711g/ml?

No you forgot to account for the volume of the water.

Offline Lodve

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Re: A rock
« Reply #6 on: August 23, 2010, 05:02:23 PM »
How am i going to do that?

Offline Borek

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Re: A rock
« Reply #7 on: August 23, 2010, 05:23:06 PM »
Final volume is initial plus volume of the solid.
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Offline opti384

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Re: A rock
« Reply #8 on: August 23, 2010, 09:25:29 PM »
Well according to Archimedes' principle, "Any object, wholly or partially immersed in a fluid, buoyed up by a force equal to the weight of the fluid displaced by the object," which means in simple words, the volume of displaced fluid is equal to the volume of the sunken object.

Offline q455923354

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Re: A rock
« Reply #9 on: August 23, 2010, 10:01:23 PM »
A rock is placed on a balance and its mass is determined as 12.1 g. When the rock is then placd in a graduated culynder that originally contains 11.3 mL og water, the new volum is roughlyhermes 17 mL. How should the density of the rock be reported?

This task doesn't seem hard at all for those who have had chemistry, but I don't know why I can't solve it. I'm relatively new here, so don't get irritated if I post easily tasks. I've never had chemistry before, so it's kinda new for me Tongue

Offline JGK

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Re: A rock
« Reply #10 on: August 24, 2010, 02:52:12 PM »
A rock is placed on a balance and its mass is determined as 12.1 g. When the rock is then placd in a graduated culynder that originally contains 11.3 mL og water, the new volum is roughly 17 mL. How should the density of the rock be reported?

This task doesn't seem hard at all for those who have had chemistry, but I don't know why I can't solve it. I'm relatively new here, so don't get irritated if I post easily tasks. I've never had chemistry before, so it's kinda new for me :P

Sorry Lodve but this isn't chemistry at all. It's mostly Mathemetics with a tiny bit of physics.
Experience is something you don't get until just after you need it.

Offline Valheru

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Re: A rock
« Reply #11 on: August 24, 2010, 07:00:21 PM »
17-11.3=5.7 ml

1 ml = 1cm³

12.1g/5.7cm³ = 2.12g/cm³

Correct me if i'm wrong

Offline Lodve

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Re: A rock
« Reply #12 on: August 26, 2010, 08:58:47 AM »
I think I just divide 12.1g to 17mL since the volume is increasing after the stone is placed on the graduated cylinder. I don't think this task wasn't meant to be that hard :P

Offline Borek

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Re: A rock
« Reply #13 on: August 26, 2010, 09:07:33 AM »
This way you are ignoring fact that you started with 11.3 mL of water.
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Offline DrCMS

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Re: A rock
« Reply #14 on: August 26, 2010, 09:41:17 AM »
I think I just divide 12.1g to 17mL since the volume is increasing after the stone is placed on the graduated cylinder. I don't think this task wasn't meant to be that hard :P

The task isn't that hard if you have a brain.  How many times do you need to be told this is wrong and that you need to take into account the volume of water before you actual listen?

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