*identify if the following are physical (p) or chemical (c) characteristics: 1) __ sodium (na) is a very reactive alkali metal. 2) __ oxygen (o) is a gas. 3) __ wood is flammable. 4) __ a ruby is red. 5) __ copper (cu) conducts electricity. 6) __ water (h2o) freezes at 0 degrees celsius. 7) __ iron (fe) reacts with water to form rust. 8) __ silver (ag) reacts with moisture in the air to form tarnish. 9) __ the chalkboard is magnetic. 10) __ sand and dirt are mixed in a flower pot.

Certain bacteria (such as aquaspirillum magnetotacticum) tend to swim toward the earth’s geographic north pole because they contain tiny particles, called magnetosomes, that are sensitive to a magnetic field. if a transmission line carrying 100 a is laid underwater, at what range of distances would the magnetic field from this line be great enough to interfere with the migration of these bacteria? (assume that a field less than 5% of the earth’s field would have little effect on the bacteria. take the earth’s field to be 5.0 * 10-5 t, and ignore the effects of the seawater.)