Experimental Design, Chemistry Review, and Properties of Water

Vocabulary flashcards covering foundational concepts in biological experimental design, basic chemistry principles, chemical bonding, chemical properties of water, and pH buffering.

Experimental Group

The group in an experiment that receives the experimental treatment (independent variable) being tested to observe its impact on the outcome (dependent variable).

Control Group

The group used for comparison to the experimental group, helping to validate statistical analysis and increase confidence in conclusions drawn from experimental results.

Independent Variable

The single factor that is changed or manipulated between groups in an experiment.

Dependent Variable

The factor that is measured in an experiment and is affected by the independent variable.

Constant

Factors kept consistent for all groups in an experiment to ensure that only the independent variable affects the outcome; also known as controlled variables.

Negative Control Group

A control group not exposed to any treatment or exposed to a treatment known to have no effect, helping to ensure that no effect occurs when none is expected.

Positive Control Group

A control group not exposed to the independent variable but exposed to a treatment known to have an expected effect, ensuring the experimental setup can produce a known result.

Matter

Anything that takes up space and has mass.

Element

A substance that cannot be broken down into other substances by chemical reactions.

Compound

A substance consisting of two or more different elements combined in a fixed ratio, such as $H_2O$ or $NaCl$.

Essential Elements

The $20\text{--}25\text{\%}$ of the $92$ naturally occurring elements that an organism needs to survive and reproduce, with CHOPN making up $96\text{\%}$ of living matter.

Trace Elements

Elements required by an organism in very small quantities, such as Iron, Zinc, Iodine, and Copper.

Octet Rule

The principle stating that elements will gain, lose, or share electrons to complete their valence shell and become stable like noble gases.

Valence Shell

The outermost layer of electrons in an atom.

Chemical Bond

An attraction between two atoms resulting from the sharing or transferring of valence electrons.

Electronegativity

The measure of an atom's ability to attract electrons to itself.

Covalent Bond

A type of bond formed when two or more atoms share electrons, typically occurring between nonmetals.

Nonpolar Covalent Bond

A covalent bond in which electrons are shared equally between two atoms, such as in $O_2$.

Polar Covalent Bond

A covalent bond in which electrons are shared unequally between two atoms, resulting in partial charges, such as in $H_2O$.

Ionic Bond

The attraction between oppositely charged atoms (ions) formed by the transfer of electrons from one atom to another, usually between a metal and a non-metal.

Cation

A positively charged ion formed when an atom loses electrons.

Anion

A negatively charged ion formed when an atom gains electrons.

Hydrogen Bond

An intermolecular attraction where a partially positive hydrogen atom in one polar covalent molecule is attracted to an electronegative atom in another polar covalent molecule.

Intermolecular Bond

A bond or force of attraction that forms between separate molecules.

Cohesion

The attraction of molecules for other molecules of the same kind, such as water molecules binding to other water molecules via hydrogen bonds.

Surface Tension

A property of liquid surfaces caused by cohesion, where surface water molecules experience a greater inward pull because there are no molecules above them to balance the forces.

Adhesion

The attraction of water molecules to other molecules that are polar or carry a charge.

Capillary Action

The upward movement of water occurring when the forces of adhesion, cohesion, and surface tension combine, specifically when adhesion to container walls is greater than cohesion.

High Specific Heat

The property of water to resist changes in temperature because heat must be absorbed to break hydrogen bonds and is released when hydrogen bonds form.

Evaporative Cooling

The process where the surface of an object becomes cooler during evaporation, caused by water requiring a large amount of energy to evaporate due to strong hydrogen bonds.

Solution

A homogeneous mixture composed of two or more substances.

Solvent

The dissolving agent in a solution.

Solute

The substance that is dissolved in a solution.

pH

A measure of how acidic or basic (alkaline) a solution is.

Acid

A substance that releases hydrogen ions ($H^+$) when dissolved in water.

Base

A substance that accepts $H^+$ ions or releases hydroxide ions ($OH^-$) in solution.

Buffer

A solution that resists drastic changes in pH when an acid or base is added, helping maintain pH stability in biological systems.