11. what is the difference between an isotope and an ion? (check all that apply) isotopes are atoms with extra electrons or too few electrons ions are atoms with extra electrons or too few electrons isotopes are atoms with extra neutrons or too few neutrons ions are atoms with extra neutrons or too few nuetrons isotopes are radioactive ions are radioactive 12. biology is the study of living things. carbon is the element that makes life possible. why is carbon so special that it is required for life? it is a positively charged ion needed in reactions. it has 4 valence electrons, so it can make 4 strong bonds with other atoms. it is a polar molecule, which makes it have a high heat capacity. because it has 4 valence electrons, it is small and only makes small compounds. 13. covalent bonds are formed when 2 atoms share electrons. ionic bonds are formed when one atom steals 1 or more electrons from another atom, creating positive and negative ions. these ions now "stick together". using the table below, which column of elements are more likely to form ionic bonds than covalent bonds? captionless image orange and yellow red and dark purple orange and blue red and light purple 14. a compound is a molecule built of 2 or more different elements. how are the properties of the compound related to the properties of the elements that make it? the compound has different properties, because the bonds cause structural changes of the elements the compound has the same properties of the atoms, because the properties of elements don't change the compound has different properties, because the elements stay the same 15. when a chemical reaction occurs, energy is either used up (absorbed) or released (given off). what is the term that describes a reaction in which there is an explosion of heat and light? endothermic exothermic ionic covalent 16. what are the reactants in the following reaction: ch4 + o2 > co2 + h20 (check all that apply) co2 o2 ch4 h2o 17. the sum of all chemical reactions in a living thing: homeostasis metabolism evolution photosynthesis 18. a catalyst is anything that speeds up a reaction. in living organisms, the protein that acts as a catalyst is an enzyme. how do enzymes speed up reactions in living things? **check all that apply by decreasing the activation energy needed to start the reaction by bringing the substrates together so the reaction can occur by increasing the energy that is needed to start the reaction 19. what does the ph scale measure? check all that apply (1/2 point each). the amount of protons in a solution. the temperature of a solution. the amount of hydrogen ions in a solution how acidic or basic a solution is 20. which of the following is a building block of proteins? monosaccharides amino acids lipids sugar 21. describe how enzymes affect chemical reactions and explain why this makes enzymes important to living things. 22. list in order the organization of living organisms, starting with the simplest and ending with the most complex.