Atoms and Elements
These four elements make up about 96% of the human body’s mass.
What are carbon, hydrogen, oxygen, and nitrogen?
This type of bond forms when electrons are transferred between atoms.
What is an ionic bond?
This property explains why sweat forms droplets on skin.
What is cohesion (via hydrogen bonding)?
Substances that start a chemical reaction are called this.
What are reactants?
The pH scale measures the concentration of these ions.
What are hydrogen ions (H⁺)?
This is the smallest unit of matter that still retains the properties of an element.
What is an atom?
What is an ionic bond?
What is a nonpolar covalent bond?
This process helps cool the body as sweat evaporates.
What is evaporative cooling?
Chemical reactions do not create or destroy this.
What is matter?
A substance that minimizes pH changes in solution is called this.
What is a buffer?
An element’s atomic number refers to this.
What is the number of protons in its nucleus?
The weak attractions between partially charged regions of water molecules are called this.
What are hydrogen bonds?
Ice floats on liquid water because it is less ___ than liquid water.
What is dense?
In photosynthesis, glucose and oxygen become carbon dioxide and water in this type of process.
What is a chemical reaction?
Compared to a pH 9 solution, a pH 4 solution has this many times more H⁺.
What is 100,000 times more?
Isotopes of an element differ in this subatomic particle.
What are neutrons?
Salt is an example of this kind of compound.
What is an ionic compound?
The ability of water to dissolve many substances earns it this title.
What is the solvent of life?
Balance the equation: C₆H₁₂O₆ + __ O₂ → __ CO₂ + __ H₂O
6 O₂ → 6 CO₂ + 6 H₂O
Ocean acidification primarily affects corals by reducing the availability of this ion.
What is the carbonate ion (CO₃²⁻)?
Explain why radioactive isotopes are useful as tracers in biological research.
They emit detectable radiation and behave chemically like stable isotopes so that scientists can track them inside organisms.
Compare polar covalent bonds in water to ionic bonds in NaCl. Why does water dissolve salt so effectively?
Water’s polarity creates partial charges that surround and separate Na⁺ and Cl⁻ ions, breaking ionic bonds and forming hydration shells.
Explain how the polarity of water contributes to its three main life-supporting properties (cohesion, temperature moderation, solvent ability).
Polarity allows hydrogen bonding, which drives cohesion and surface tension, stabilizes temperature through heat absorption and release, and attracts/dissolves charged or polar solutes.
Why do we say that chemical reactions in cells are about rearranging atoms, not creating or destroying them?
Atoms are conserved; bonds break and reform to change molecular structures without altering the total number of atoms.
Identify the independent and dependent variables in the experiment testing coral calcification under reduced carbonate concentration.
Independent variable = carbonate ion concentration; Dependent variable = rate of calcium deposition by reef organisms