Unit 1

Matter

Anything that occupies space, has mass, and is made up of elements.

Element

A substance made up of only one type of atom that can't be broken down into a simpler chemical substance.

CHNOPS (Six Most Common Elements)

The six most common elements in living things: Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, and Sulfur.

Trace Elements

Elements required by an organism in only very small amounts (e.g., iron, which carries oxygen, and iodine, which is essential for a thyroid hormone).

Atoms

The smallest building blocks of matter that retain the characteristics of that element. They cannot be divided into smaller substances by any natural processes.

Nucleus

Small central part of an atom that contains the protons and neutrons.

Proton

An atomic particle with a positive charge and a mass of 1, located in the nucleus.

Neutron

An atomic particle with a neutral charge and a mass of 1, located in the nucleus.

Electron

An atomic particle with a negative charge and nil mass, located orbiting the nucleus.

Atomic Number

The number of protons in an atom.

Mass Number

The sum of the number of protons and neutrons.

Isotopes

The same type of atom, but they have different numbers of neutrons. They have the same number of protons and behave identically in chemical reactions.

Radioactive Isotopes

Isotopes whose nucleus decays spontaneously, causing particles and energy to be given off.

Electrons (in bonding)

The only atomic particles directly involved in the chemical activity of an atom. The further they are from the nucleus, the greater their energy.

Electron Shells

Different energy levels around the nucleus where electrons can be located.

Valence Electrons

Electrons located in the outermost electron shell. They participate in chemical bonding.

Chemical Bond

Formed when atoms interact by sharing, gaining, or losing valence electrons to achieve a full (stable) outermost shell.

Covalent Bond

A strong chemical bond that forms when two atoms share electrons. It is the strongest type of bond.

Nonpolar Covalent Bond

A bond where the electrons are shared equally between the atoms (e.g., between two atoms of the same element, like O_2).

Polar Covalent Bond

A bond where the electrons are shared unequally because one atom is more electronegative (a stronger pull on electrons) than the other (e.g., in a water molecule, H_2O).

Ion

An atom or molecule with an electrical charge as a result of gaining or losing valence electrons.

Ionic Bond

Occurs when two ions of opposite charges attract one another. It forms when electrons are lost or gained, typically between a nonmetal and a metal, to create a stable outer shell. It is the next strongest bond after covalent bonds.

Hydrogen Bond

Tends to form between the negatively charged region of an atom (like Oxygen) and a hydrogen atom. It is the weakest type of bond and is crucial for the functioning of a cell and creating the unique 3D shape of molecules (like in DNA).

Chemical Reaction

The process of breaking and making chemical bonds, which changes the composition of matter by converting reactants (starting materials) into products (resulting materials). Matter is only rearranged, not destroyed.

Polarity (of Water)

The uneven distribution of electrons in a water molecule, where electrons are pulled toward the oxygen atom, giving it a partial negative charge and the hydrogen atoms a partial positive charge.

Hydrogen Bonding (in Water)

The attraction between the partial negative charge on the oxygen of one water molecule and the partial positive charge on the hydrogen of another water molecule, which links water's life-supporting properties.

Cohesion

A property of water where molecules of the same substance stick to one another (e.g., water sticking to water). It creates surface tension.

Adhesion

A property of water where molecules of different substances stick to one another.

Surface Tension

The force that allows objects (like a paper clip or certain insects) to rest on the surface of water without breaking the surface. It is related to cohesion.

Specific Heat

Water's ability to resist changes in temperature, meaning it can absorb a lot of heat before its temperature increases. This helps organisms maintain a stable internal temperature (homeostasis).

Density (of Ice)

The property that makes ice less dense than liquid water (ice floats). This is important because it allows aquatic life to survive below the frozen surface.

Aqueous Solution

A solution where the solute particles are evenly distributed throughout the solvent, with water being the solvent.

Solute

The substance that is being dissolved in a solution.

Solvent

The substance that is doing the dissolving in a solution.

Universal Solvent

The term used to describe water due to its ability to dissolve practically any molecule.

Acid

Any compound that forms H+ ions in solution. These solutions have pH values that fall below 7. Strong acids usually have a pH between 0 and 3.

Base

A compound that produces OH- ions in solution. These solutions have pH values that fall above 7. Strong bases usually have a pH between 11 and 14.

pH Scale

Used to describe how acidic or basic a solution is, based on the concentration of H+ and OH- ions.

Buffer

A substance that helps keep the pH of a solution constant by preventing sharp, sudden changes in pH. They are vital for maintaining homeostasis in living systems