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Which six elements provide most of the mass of biological organisms?
- C, O, N, H, P, S (carbon, hydrogen, nitrogen, oxygen, sulphur and phosphorus)
How many electrons occupy the orbital in the first energy level of an oxygen atom?
- Two
The opposite of hydrophobic is
- hydrophilic.
Oxygen (O) has an atomic number of 8. What is the approximate atomic mass of an oxygen atom in daltons?
16
An aqueous solution with a mixture of a _______ acid and its corresponding ___ is called a(n) _______.
- weak; base; buffer
Refer to the figure. (Click image to enlarge.)
An oxygen atom by itself is very reactive, whereas an oxygen atom that has combined with two hydrogen atoms to form a water molecule is very stable. What explains this observation?
- An oxygen atom only has six electrons in its valence shell and needs two electrons from hydrogen to fill this shell.
Refer to the table showing the percentage abundance of elements by mass in five different samples. (Click image to enlarge.)
Which sample was taken from a living organism?
-5
Which pair of atoms would be expected to have similar chemical properties?
- 24/12 Mg and 80/38 Sr
Which is an example of how water's high heat of vaporization affects a living organism?
- Mammals produce sweat, which cools their bodies by absorbing excess body heat as the water in sweat evaporates.
Which statement could be used to explain why an atom is electrically neutral?
- The atom contains an equal number of protons and electrons.
In the periodic table, why are hydrogen, lithium, and sodium in the same column?
- They have the same number of unpaired electrons.
Vegetable oil is composed of long-chain hydrocarbon molecules. Vegetable oil and water do not mix but form separate layers. Which statement describes the interactions between molecules in this case?
- The water molecules interact through hydrophilic interactions, and the hydrocarbon molecules interact through hydrophobic interactions.
The subatomic particles that determine the _______ of an atom are _______. QQ`1
- charge; electrons and protons
Refer to the figure showing four examples of molecular interactions in biological samples. (Click image to enlarge.)
Identify the examples as either hydrophilic or hydrophobic interactions, or neither.
- 2 and 3 are hydrophilic; 4 is hydrophobic
Although air temperatures at a site on the coast of California can swing widely in very short periods of time, marine animals in the ocean at this site do not experience the same wide temperature swings. Which statement explains this observation?
- A great deal of energy absorbed by water goes into breaking hydrogen bonds between water molecules.
What is true about an atom that has no charge?
- It has equal numbers of electrons and protons.
Which statement provides evidence that living organisms undergo constant change?
- Living organisms are composed of cells that function using chemical reactions.
