Questions and Answers
Hydrophobic substances such as vegetable oil are:
Wax is a:
Hydrophobic molecule
An atom is the smallest unit of an element that still retains properties of the element.
true
All atoms of a particular element have different numbers of protons in their nuclei.
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Atoms of various molecules differ in their number of:
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Neutrons and protons are equal in mass.
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Neutrons and protons have a mass of approximately:
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Buffers are substances that help resist shifts in pH by _____ and _____
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The mass number of an element can be easily approximated by adding together the number of:
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In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by:
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The slight negative charge at one end of a water molecule is attracted to the slight positive charge of another molecule. This attraction is called a:
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A solution containing $10^{-7}$ moles of hydroxyl ions [OH-] per liter is:
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What is the approximate mass of an atom with 16 neutrons, 15 protons, and 15 electrons?
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A covalent bond is likely to be polar when:
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Many mammals control their body temperature by sweating, caused by which of water's properties?
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Atoms whose outer electron shells contain 8 electrons are:
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A system that maintains a relatively constant pH when either acids or bases are added is called a:
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The atomic number indicates the number of:
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Blood that comes in contact with respiring cells will:
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Why does ice float in water?
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If pure, freshly distilled water has [OH-] = [H+], then the pH is:
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Weak interactions include:
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What four elements make up 96% of living matter?
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Water striders are an example of:
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4 degrees is water's:
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A covalent chemical bond is formed when:
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If you mix two beakers together with different pHs, the new pH will be the:
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What gives rise to the cohesiveness of water molecules?
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Study Notes
Key Concepts in Biology
- Hydrophobic substances, like vegetable oil, are nonpolar and repel water.
- Waxes are classified as hydrophobic molecules, contributing to waterproofing in various organisms.
- An atom is the smallest unit of an element, retaining the element's properties.
- Atoms of a particular element have identical numbers of protons in their nuclei, defining the element.
- Different atoms comprise various molecules, differentiated by varying numbers of subatomic particles.
- Neutrons and protons have equal mass, approximately 1 Dalton (also known as atomic mass unit or amu).
- Buffers stabilize pH levels by donating H+ when depleted and accepting H+ when in excess.
- The mass number of an element approximates the sum of its protons and neutrons.
Water and Its Properties
- Water molecules consist of two hydrogen atoms bonded to one oxygen atom via polar covalent bonds.
- The slight charges of water molecules lead to hydrogen bonds, a key reason for interactions between water molecules.
- A solution with 10^-7 moles of hydroxyl ions (OH-) per liter is neutral, indicating equal concentrations of H+ and OH-.
- For an atom with 16 neutrons, 15 protons, and 15 electrons, the approximate mass is 51 Daltons.
- Polar covalent bonds are likely when one of the atoms is significantly more electronegative.
- Many mammals regulate body temperature through sweating, a process involving the heat absorption when hydrogen bonds break.
- Atoms with eight electrons in their outer shell are considered stable, chemically inactive, or inert.
Chemical Interactions and Solutions
- A buffer system maintains consistent pH despite the addition of acids or bases.
- Atomic number indicates the number of protons in an atom's nucleus, which determines the element's identity.
- Blood interacting with respiring cells typically experiences a slight decrease in pH due to metabolic processes.
- Ice floats on water because hydrogen bonds create a stable structure that keeps ice molecules farther apart than those in liquid water.
- Pure, freshly distilled water has equal concentrations of H+ and OH-, resulting in a neutral pH of 7.
- Weak interactions such as ionic bonds, van der Waals interactions, and hydrogen bonds play crucial roles in molecular structure and function.
Elements and Nature
- Four elements—carbon, hydrogen, nitrogen, and oxygen—make up approximately 96% of living matter.
- The high surface tension of water is illustrated by the behavior of water striders, allowing them to walk on water.
- Water's densest point occurs at 4 degrees Celsius, an unusual property that influences aquatic ecosystems.
- Covalent bonds involve the sharing of outer-shell electrons, essential for forming stable molecules.
- Mixing two solutions with different pHs leads to a new pH that is the average of the two.
- Cohesiveness in water molecules arises from hydrogen bonding, enabling phenomena such as surface tension and capillarity.
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Test your knowledge of key concepts from AP Biology Chapters 2 and 3 with this set of flashcards. Explore essential terms like hydrophobic substances, atoms, and their properties. Perfect for quick review or study sessions!