6. Krystal is exploring the properties of iron. She takes a large iron nail and finds that the nail does not attract other metal objects. Next, she uses a battery and copper wire to transform the nail into an electromagnet. When she connects the circuit, the nail becomes magnetic and can pick up small metal objects like paper clips. What best describes what has happened to the iron in the nail that causes it to become magnetic?

A. A physical change has occurred, because the chemical properties of the iron remain the same.

B. A physical change has occurred, because there is a chemical attraction between the iron and paper clips.

C. A chemical change has occurred, because there is a chemical attraction between the iron and paper clips.

D. A chemical change has occurred, because the chemical energy in the battery is transformed into magnetic energy in the iron.

What came first egg or chicken? and is tomato a vegetable or a fruit?

Rease is an enzyme used by plants to break down urea (a nitrogen-containing compound) into carbon dioxide and ammonia. urease urea > > > carbon dioxide and ammonia ammonia is broken down by plants into a nitrogen source plants need to grow. thus, plants could not use urea as a nitrogen source unless it was first converted to ammonia. in soybean plants there are two different kinds of urease, one produced in the seeds and the other produced in the leaves of the plant. three types of soybean plants were used in a set of experiments: normal soybeans and two mutant strains, one lacking the urease in the seeds only (strain 1) and one lacking urease in the leaves only (strain 2). experiment 1 separate areas in a field were planted with normal, strain 1, and strain 2 soybeans. all types of soybeans appeared to grow, flower, and produce seeds equally well. there were no externally detectable differences among the strains. experiment 2 small pieces of plant leaves of equal weight were obtained from each type of soybean plant and separately placed on media in culture dishes. tissue growing in this way will become an unorganized clump of cells referred to as callus. to provide a controlled nitrogen source, half the tissue samples of each type were placed on media containing urea, and the other half of the samples were placed on media containing ammonia. after 30 days, the weight gain for each of the callus samples was determined. results are shown in the table below.

The tubes transporting minerals and water upward are called ?