AP Biology: Chapter 2/3 Flashcards

Questions and Answers

Hydrophobic substances such as vegetable oil are:

Substances that dissolve in water

Polar substances that attract water

Ionic substances

Nonpolar substances that repel water molecules (correct)

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.

False Signup and view all the answers

Atoms of various molecules differ in their number of:

Subatomic particles Signup and view all the answers

Neutrons and protons are equal in mass.

True Signup and view all the answers

Neutrons and protons have a mass of approximately:

1 Dalton (amu) Signup and view all the answers

Buffers are substances that help resist shifts in pH by _ and _

donating H+, accepting H+ Signup and view all the answers

The mass number of an element can be easily approximated by adding together the number of:

Protons and neutrons Signup and view all the answers

In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by:

Polar covalent bonds Signup and view all the answers

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:

Hydrophilic bond Signup and view all the answers

A solution containing $10^{-7}$ moles of hydroxyl ions [OH-] per liter is:

Neutral Signup and view all the answers

What is the approximate mass of an atom with 16 neutrons, 15 protons, and 15 electrons?

51 Daltons Signup and view all the answers

A covalent bond is likely to be polar when:

One of the elements sharing electrons is much more electronegative than the other. Signup and view all the answers

Many mammals control their body temperature by sweating, caused by which of water's properties?

The absorption of heat by the breaking of hydrogen bonds Signup and view all the answers

Atoms whose outer electron shells contain 8 electrons are:

Stable/chemically inactive/inert elements Signup and view all the answers

A system that maintains a relatively constant pH when either acids or bases are added is called a:

Buffer system Signup and view all the answers

The atomic number indicates the number of:

Protons in an atom's nucleus Signup and view all the answers

Blood that comes in contact with respiring cells will:

Have its pH decrease slightly Signup and view all the answers

Why does ice float in water?

Hydrogen bonds stabilize the molecules of ice and keep them farther apart than the water molecules of liquid water Signup and view all the answers

If pure, freshly distilled water has [OH-] = [H+], then the pH is:

7 Signup and view all the answers

Weak interactions include:

Ionic bonds, Van der Waals interactions, and hydrogen bonds. Signup and view all the answers

What four elements make up 96% of living matter?

Carbon, Hydrogen, Nitrogen, Oxygen Signup and view all the answers

Water striders are an example of:

Water's high surface tension Signup and view all the answers

4 degrees is water's:

Densest point Signup and view all the answers

A covalent chemical bond is formed when:

Outer-shell electrons of two atoms are shared to satisfactorily fill the outer shell electron shells of both atoms Signup and view all the answers

If you mix two beakers together with different pHs, the new pH will be the:

Average of their two pHs Signup and view all the answers

What gives rise to the cohesiveness of water molecules?

Hydrogen bonds Signup and view all the answers

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!