2 the size of the electrons The way in which elements bond to form compounds depends on which of the following?the size of the electronsthe shape of the nucleusthe number of neutrons in each atomthe electrons in the atoms of the elements
3 In what type of bond are electrons shared? ionicnuclearcovalenthydrogen
4 ionic nuclear covalent hydrogen What weak bond holds together the two strands of nucleotides in a DNA molecule?ionicnuclearcovalenthydrogen
5 The substance is an acid When an unknown substance is dissolved in water, hydronium ions form. What can you conclude about the substance?The substance is a gasThe substance is a basThe substance is an acidThe substance is a carbohydrate
6 Activation energy is needed only by chemical reactions that release
7 In an atom, the number of protons is equal to the number of electrons.
8 A solution is a mixture of unevenly distributed substances
9 Polar substances dissolve well in water because water also is polar
10 Most of the chemical reactions in the body would not occur without enzymes
12 The attraction between water molecules is caused by covalent bondhydrogen bondsionic and covalent bonds
13 An atom is called an ion when it has either lost or gained electronslost its nucleusmore neutrons than protons
14 The ability of water to form drops is an example of adhesion.cohesion.ionic bonding
15 Both solutions are acidic One solution has a pH of 2, and another has a pH of 7. Which of the following is true?Both solutions are acidicThe solution with a pH of 2 is basic, and the solution with a pH of 7 is acidic.The solution with a pH of 2 is acidic, and the solution with a pH of 7 is neutral.
16 Plants store the sun’s energy for future use as DNAstarch.protein.
17 decrease the speed of chemical reactions. Enzymesare usually proteins.decrease the speed of chemical reactions.increase the activation energy of chemical reactions
18 element. atom. molecule. electron. The smallest unit of matter that cannot be broken down by chemical means is a(n)element.atom.molecule.electron.
19 The bonds between the atoms that make up water molecules are called covalent bondhydrogen bondsionic and covalent bondcovalent and hydrogen bonds.
20 An atom is called an ion when it ha either lost or gained electrons.either lost or gained protons.more neutrons than protonslost its nucleus.
21 A solution is a mixture of polar and nonpolar substancesprotons and neutrons.unevenly distributed substances.evenly distributed substances.
22 Water is _______ , therefore _______ substances dissolve in it. polar, nonpolarpolar, polarnonpolar, polarnonpolar, nonpolar
23 In a chemical reaction, energy may be absorbed.released.required.All of the above
24 Without energy, organisms could not maintain homeostasis.carry out chemical reactions.make their own food.All of the above
25 The basic units of most biomolecules contain nitrogen.oxygencarbon.amino acids
26 Compounds are formed when atoms of an element lose an electron.atoms of an element gain an electronatoms of the same element join together.atoms of two different elements join together.
27 are usually carbohydrates. Enzymesare usually carbohydrates.can only catalyze a reaction oncreduce the activation energy of chemical reactionseliminate the activation energy of chemical reactions.
28 impossible to determine. In an atom with the same number of electrons and protons, the electrical charge isneutral.positive.negative.impossible to determine.
29 Activation energy is needed by chemical reactions that release energyabsorb energy.are catalyzed by enzymes.All of the above
30 The ability of water to form drops is an example of a chemical change.cohesion.adhesionionic bonding
31 What kind of bonds do water molecules form with one another? covalenthydrogenionicBoth (a) and (c)
32 is made of a sugar, a base, and a phosphate group Starchis made of a sugar, a base, and a phosphate groupdoes not contain carbon atoms.is made of amino acidsis a carbohydrate in which energy is stored
33 2. Solution B indicates a pH of 7. You conclude that Two solutions, A and B, are tested for pH. Solution A indicates a pH of2. Solution B indicates a pH of 7. You conclude thatboth solutions are acidic.solution A is basic; solution B is neutral.solution A is acidic; solution B is neutralNone of the above
34 compound. molecule. atom. ion. An element is defined as a pure substance because it is made of only one kind ofcompound.molecule.atom.ion.
35 Atoms bond with other atoms to form compounds because electrons are attracted to each otherbonding helps atoms become more stable.the nuclei of atoms are attracted to each other.bonding makes an element more pure.
36 When food molecules are broken down inside cells, some of the energy in the molecules is stored temporarily inproteins.RNA.DNA.ATP.
37 do not take part in the reaction. Enzymes that take part in a chemical reaction are not considered to bereactants because theydo not take part in the reaction.are not changed by the reaction.have no valence electrons.are used up in the reaction