Chapter 2 11a. science is best described as a random collection o 11b. the terrestrial ecosystems with net primary the lowest net primary productivity are swamps and marshes. 12a. when scientists are testing ideas to determine facts, they follow a s 12b. scientific laws differ from scientific theories in that they are tentative pecific set of logical steps. explanations that need further evaluation. 13a. the following sequence is what scientists typically use in the beginning stages of their investigations nature works: indentify a problem search literature develop a hypothesisperform 13b. matter is anything that has the capacity to do work. e experimentgather and analyze data formulate a conclusion-> report findings . 14a. the building blocks of matter are molecules and compounds. 14b. the following compound is an anion: nh 15a. a positive feedback loop reverses the direction the system is going 15b. the atomic mass number is equal to the sum of the protons and neutrons in the atom. 16a. isotopes differ from each other by their number of neutrons. 16b. lons are atoms or groups of atoms that have gained or lost a neutron. 17a. heat dispersed in the ocean and the battery that operates your laptop computer are examples of lower 17b. energy input energy output is the best description of the first law of thermodyn 18a. when matter undergoes a physical change, its size and shape may change, but the arra 18b. the law of conservation of matter states that atoms cannot be created or destroyed. quality energy. atoms remains the same. 19a. the four organic macromolecules are lipids, nucleic acids, proteins, and simple carbohydrates. 19b. electricity flowing through a wire is an example of potential energy aluminum. examine the box below which has periodic table information about the element 20a. the atomic number of aluminum is 27 20b. aluminum has 13 protons and 14 neutrons 13 al aluminum 27.0