Atomic Structure & Elements
What is the smallest unit of an element that still retains the properties of that element?
An atom
What type of chemical bond forms when two atoms share electrons?
A covalent bond
What term describes the attraction between water molecules and other water molecules?
Cohesion
In a sugar water mixture, what is the solvent and what is the solute?
Water is the solvent, and sugar is the solute
What term refers to new properties that arise when individual parts combine and interact to form a new complex substance?
Emergent properties
Name the four elements that make up approximately 96% of the mass of living organisms (often remembered by the acronym CHON)
Carbon, Hydrogen, Oxygen, and Nitrogen
What term describes an atom's "pulling power" or ability to attract shared electrons towards itself?
Electronegativity
Why is liquid water denser than solid ice, causing ice to float?
When water freezes, hydrogen bonds hold the molecules in a fixed, organized structure that keeps them farther apart (increasing volume and decreasing density).
What general chemistry rule explains why polar or charged substances easily dissolve in water, while nonpolar substances like oil do not?
Like dissolves like
What is the correct hierarchy of biological organization starting from matter up to a whole living organism?
matter->elements->atoms->molecules->cells->organisms.
Which subatomic particle determines an atom's identity, such that changing its number creates a completely different element?
The proton (or atomic number)
When electrons are shared unequally between two atoms in a covalent bond, what kind of bond is formed?
A polar covalent bond
What property allows water striders and some small insects to walk across the surface of water without sinking?
Surface tension
How does sweating cool down your body during exercise?
Answer: Through evaporative cooling—the highest-energy (fastest) water molecules escape into the air first, leaving behind slower molecules and lowering the average temperature of the remaining liquid.
Why is a molecule like H2O classified as both a molecule AND a compound, whereas H2 is only a molecule?
H2O consists of two different elements chemically combined, whereas H2 contains only one element
How do you calculate the mass number of an atom?
the number of protons and neutrons
According to the octet rule, how many valence electrons do most atoms need in their outermost shell to become stable?
8 valence electrons (with exceptions like Hydrogen and Helium, which need 2)
What two properties work together to help pull water upward through the xylem of plants against gravity?
Cohesion (water sticking to water) and adhesion (water sticking to the walls of the plant cells).
How do water molecules dissolve an ionic compound like table salt?
The slightly negative oxygen ends attract positive sodium ions , and the slightly positive hydrogen ends attract negative chloride ions, pulling them apart and surrounding them
Within a single water molecule, what type of bond holds the hydrogen atoms to the oxygen atom?
Polar covalent bonds
though they are required in extremely small quantities, elements like Iron (Fe) and Iodine (I) are necessary for survival and are known by this term
Trace elements
What specific weak attraction occurs between a slightly positive ($\delta+$) hydrogen atom of one molecule and a slightly negative ($\delta-$) electronegative atom (like oxygen) of a neighboring molecule?
A hydrogen bond.
Why does water have a high specific heat?
Much of the added heat energy is used to break/disrupt hydrogen bonds before the water molecules can move faster and raise the temperature.
Why are large bodies of water, such as oceans, effective at moderating regional climate temperatures?
Water's high specific heat allows oceans to absorb large amounts of heat during warm periods without a drastic temperature change, and slowly release that heat when surroundings cool
What Latin-derived symbol stands for Sodium, and what is its valency?
Symbol: Na (from natrium); Valency: 1.