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Answers to Concept Check 9. Due to its polarity, water is attracted to the
positive and negative ions of sodium chloride.
and Review Questions When water’s slightly positive H atoms are close
-
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to the Cl , and its slightly negative O atom is
+
close to the Na of the NaCl crystal, the water
eventually surrounds the ions and dissolves them
Module 0 Module 1 into the water itself.
10. The reactants are the three H 2 and one N 2
✓ Concept Check 0.1 ✓ Concept Check 1.1 molecules, and the product is the two NH 3
1. A comparison of a fire ant with an army ant 1. Matter cycles within living systems and the molecules.
will note the unity of life because both groups environment. This means that matter is reused ✓ Concept Check 1.4
have the same general segmented body plan. over and over again. By contrast, energy is not
It will also show the diversity of life because reused. Instead, energy flows through living 11. The four most common atoms in organic
the mandibles, abdomens, and heads of the two systems and an input of energy is constantly molecules are carbon, hydrogen, oxygen, and
groups vary significantly in their structures and required to sustain life. nitrogen.
sizes. 12. Carbon requires four electrons to fill its outer
2. The energy input for most habitats on Earth
2. A lack of energy would result in an organism comes from the sun. Plants and other organisms shell, which allows it to form covalent bonds
being unable to carry out its cellular functions, convert energy from the sun into chemical with four other atoms. As a result, carbon-based
maintain itself, grow, and reproduce, which energy in the form of carbon-rich organic molecules are very diverse.
would eventually cause death. molecules. Other organisms eat these carbon- 13. The four major types of organic molecules
rich organic molecules for sources of both matter
3. Without being able to retrieve information and energy to survive, grow, reproduce and so on. are proteins, nucleic acids, carbohydrates, and
contained in their genes, organisms would be As a result, the movements of carbon and energy lipids.
unable to respond to environmental changes and are intimately related. 14. A polymer is a molecule built of many small,
could not perform functions such as growth and repeating subunits.
reproduction. ✓ Concept Check 1.2
4. The Canada lynx, using the systems of its 3. An atom’s components are the protons and 15. Lipids, being hydrophobic, associate with
each other and not water, so provide a barrier
eyes, nose, brain, nerves, bones, and muscles, is neutrons of its nucleus and the electrons that between the inside and outside of a cell, which is
able to note the presence of the snowshoe hare, travel around the central nucleus. water based.
close in on the hare, and give chase that may
result in the capture of the hare. This would 4. The periodic table is organized in rows Review Questions
and columns. Rows consist of elements with
not be possible without the interaction of these 1. B; 2. C; 3. A; 4. D; 5. C; 6. C; 7. B
systems. increasing numbers of protons and electrons in
each successive element until the end of the row,
✓ Concept Check 0.2 where the outermost level is now complete with Module 2
5. A scientist uses observation to propose electrons. Vertical columns define elements with
similar chemical properties, and which have the
a testable explanation of how, or why, the same number of electrons in their outermost level. ✓ Concept Check 2.1
observation occurs. This is the hypothesis. The 1. Water is a polar molecule; its hydrogen atoms
14
scientist investigates the hypothesis either by 5. N means that the atomic mass of the element are partially positive and its oxygen atom is
15
conducting further observations or through is 14, while N means that it has a mass of 15. partially negative. This polarity makes hydrogen
15
experimental investigation, or both. This is because N and N have seven protons bonding possible because the partially negative
14
14
in their nuclei, but N has seven neutrons and
6. An experimental group is one in which an 15 N has eight neutrons in its nucleus. oxygen atom is attracted to the partially positive
independent variable is changed to determine hydrogen atom of another water molecule.
if the dependent variable changes because of it. 6. Four more electrons would bring carbon to 2. Water’s hydrogen bonding gives water many
A control group doesn’t change the independent eight electrons in its outer level, which would of its characteristics, such as cohesion, adhesion,
variable, and whether the dependent variable make the level complete. surface tension, and high specific heat.
changes or not is also observed. It is important to
have both a control and an experimental group if 7. Electrons furthest from the nucleus have the ✓ Concept Check 2.2
the researcher is to determine that changing the most energy, while those closest have the least
independent variable does change the dependent amount of energy. 3. Due to its hydrogen bonds, water can surround
an ammonia molecule and separate it from
variable. ✓ Concept Check 1.3 other ammonia molecules. Once the ammonia
7. A guess is a hunch about something, while 8. A covalent bond is formed when electrons molecule is completely surrounded by water, it
a hypothesis is a tentative explanation as to from two different atoms are shared in the is dissolved.
why an observation occurred. A theory, in a outermost shells of each atom. A polar covalent 4. The hydrogen atom of water binds to the
scientific sense, is a set of hypotheses about a bond occurs when the shared electrons are not
particular natural phenomenon that has gained shared equally and one atom more often has nitrogen atom of ammonia, and the oxygen
atom of water binds to the hydrogen atom of
considerable scientific support via observation or the electrons nearer to itself than does the other
experimental examination. atom. In nonpolar covalent bonds, electrons are ammonia.
shared equally by the atoms. In an ionic bond, 5. It is slightly basic because it has a higher value
Review Questions two ions with opposite electrical charges attract than 7.0, which means that it has fewer H than
+
−
1. B; 2. C; 3. B; 4. D; 5. A; 6. D; 7. C each other because of the differences in charge. OH ions.
ANSWERS ANS-1

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