A biology class wanted to study the effect of different materials on the melting rate of ice. They placed pieces of ice, each with a mass of 10g, onto trays. Group 1 was covered in plastic, group 2 was covered in paper, group 3 was covered in aluminum, and group 4 remained uncovered. Each piece of ice was allowed to melt for 15 minutes. Then final mass of the ice, minus the melted water, was recorded at the end of the experiment.
What is the independent variable in this experiment?

ability to bond woth oxygen

interphase

the period of cell growth when the cell synthesizes new molecules and organelles. the cell is not dividing and it constitutes the majority of the time spent in the cell cycle

prophase

changes occur in the nucleus and cytoplasm. the chromatin condenses to form structures (sister chromatids) visible with a light microscope and the mitotic spindle begins to form, but the nucleus is still in tact

prometaphase

the nuclear envelope fragments and the spindle microtubules attach to the kinetochores of the sister chromatids

metaphase

all the cell's duplicated chromosomes are lined up at an imaginary plane equidistant between the poles of the mitotic spindle

anaphase

begins when sister chromatids separate from each other and ending when a complete set of daughter chromosomes arrives at each of the two poles of the cell

telophase

the daughter nuclei form at the two poles of a cell

cytokinesis

the division of a cytoplasm to form two separate daughter cells. usually occurs during telophase during mitosis. this and mitosis make up to mitotic (m) phase of the cell cycle