# Homework Help: Help for a basic (to some) program

1. Apr 5, 2004

### SigInt

Help for a basic (to some) problem (didn't mean program)

I have 5 questions that I need help with. I'll give my answer and I just need clarification on whether or not its wrong and how I can correct it.

1.) A block is placed in two differnt liquids. It floats in both, but with different volumes immersed. The liquid in which it displaces the larger volume is a compound while the other liquid is an element, and both substances have the same number of particles per unit volume. Could the molecules of the compound have a larger mass than the atoms of the element? Explain Fully.

-- No, because if the molecules had a larger mass than the block would float instead of sink. (Thats my way of thinking, but physics isn't something I really understand without a book. My teacher doesn't teach that way. )

2.) Two blocks, one made of a compound and one of an element, are placed in the same liquid. The two blocks displace the same volumes and both float. If the mass of the atoms is the same as the mass of the molecules, how does the number of particles in these two blocks compare? Explain Fully.

-- (this one is making me crazy) I think the numbers of particles are different because both blocks are two different substances and one has more particles than the other.

Last edited: Apr 5, 2004
2. Apr 5, 2004

### Janitor

1. The compound has a lower mass density than the element. So for equal volumes, it would have less mass, but we are told that for equal volumes, it has same particle number. The mass of a single molecule must thus be less than the mass of the single atom, so you are correct when you say "no."

2. Since the same volume of liquid is displaced, the mass of the two blocks is the same. Since we are told the molecule has the same mass as the atom, it must be the case that the number of molecules in the one block is the same as the number of atoms in the other block.

Last edited: Apr 5, 2004
3. Apr 5, 2004

### SigInt

so your saying for 1.) they are even since they have the same number of particles?

and for 2.) your saying that they too are even because the mass is the same for the compound and the element?

4. Apr 6, 2004

### Janitor

"1.) they are even since they have the same number of particles?"

I'm not quite sure what you mean by "they are even" in this particular context, so I will just repeat that the mass of the molecule and the mass of the atom are not the same, or "not even," if you prefer to say it that way.

2. "they too are even because the mass is the same for the compound and the element?"

That is probably a fair thing to say. Note that the densities of the two blocks could very well be different from one another, in this second case.

Last edited: Apr 6, 2004
5. Apr 6, 2004

### SigInt

what I mean to say was equal.

6. Apr 6, 2004

### Janitor

1. mass of molecule < mass of atom

2. number of molecules in one block = number of atoms in other block

So since you mean "equal" when you say "even," then I am saying "no" to Q1 and "yes" to Q2. I hope this clarifies things.