Re: 'If I had a strong enough magnet, could I lift spinach

Ms. Bauer,
     The answer is a qualified yes.  I am not certain, but it seems likely 
that a strong enough field could in fact levitate a piece of spinach.  
However, I don't think that such a field could be realistically produced.
     I imagine that you selected spinach to try and levitate because of the 
high iron content in that vegetable.  The problem with such reasoning is 
that not all iron is strongly magnetic.  Metallic iron is ferromagnetic.  
It can have a field of its own, even when no external fields are present.  
It responds very strongly to other magnetic fields, and will feel strong 
forces due to those fields.
     The reason metallic iron is ferromagnetic is because of the way that 
the electrons in the iron atoms interact with electrons in other iron 
atoms.  These interactions can be disrupted by changing the arrangement of 
iron atoms.  For instance, steel has a large amount of iron in it, and most 
steel alloys are ferromagnetic.  Certain kinds of steel (stainless steel) 
are not ferromagnetic if you don't abuse them (getting them very hot is 
one way to do that).  Iron oxide is not magnetic.  The iron in spinach is 
organically bound iron.  That means it is present as part of an organic 
molecule, and is not ferromagnetic.  If you want to know more about 
ferromagnetism, you might try this 
 
previous answer
 which also lists some references.
     The iron present in spinach probably causes it to be slightly 
paramagnetic.  You can think of this as being weakly magnetic.  
Paramagnetic materials cannot have a field of their own, and respond to 
other fields with varying degrees of strength.  For instance, a friend of 
mine once levitated a glob of liquid nitrogen that had lots of dissolved 
oxygen in a strong magnet.  By itself, liquid nitrogen is not magnetic.  
The dissolved oxygen is paramagnetic, and will respond weakly to another 
magnetic field.  The magnet in question was extremely powerful, and there 
was lots of dissolved oxygen in the nitrogen.  My friend found that if he 
decreased the amount of oxygen in the nitrogen, that he couldn't float the 
glob anymore.
      So with a powerful magnetic field, and a sufficient density of 
paramagnetic material, you can levitate something that is not otherwise 
magnetic.  If the density of the paramagnetic substance is too low, you 
will need a more powerful field.  If you look here you will 
find that the recommended daily allowance of iron is 10-15mg.  A single 
serving of spinach (85g) contains 20% of the RDA.  So there is 2-3mg of 
iron in the spinach, or about 30 parts per millon by weight.  This isn't 
very much, so it would take such a strong field to levitate the spinach 
that I doubt it could be produced.  For the record, the field my friend did 
his experiment in was 9.4 Tesla.  The largest sustained field I am aware of   
is 35 Tesla, but there might be larger ones around.  I would guess that the 
field necessary to levitate spinach would have to be hundreds of times 
larger than the fields I mentioned.
                                                        John