Chapter 2 (Campbell's Biology in Focus)

Concept 2.1

• ==Matter== is anything that takes up space and has mass
• ==An element== is a substance that cannot be broken down into other substances by chemical reactions
• ==A compound== is a substance consisting of two or more different elements combined in a fixed ratio
• ==Essential elements== are natural elements that an organism needs to live a healthy life and reproduce
• ==Trace elements== are required by an organism in only minute quantities

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Subatomic Particles

• The three main parts of an atom are
• neutrons
• protons
• electrons
• The unit of measurement for atoms and subatomic particles is a ==dalton==
• Different atomic forms of the same element are called ==isotopes==
• A ==radioactive isotope== is one in which the nucleus decays spontaneously giving particles and energy
• ==Potential energy== is the energy that matter possesses because of its location or structure

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Electrons Distribution and Chemical Properties

• electrons are found in different electron shells
• The chemical behaviour of an atom depends mostly on the number of electrons in its outermost shell
• These electrons are called ==valence electrons== and are found in the ==valence shell==

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The formation and function of molecules depend on chemical bonding between atoms

• Attractions between atoms are called ==chemical bonds==
• A ==covalent bond== is the sharing of a pair of valence electrons by two atoms
• Two or more atoms held together by covalent bond constitute a ==molecule==
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• The attraction of a particular atom for the electrons of a covalent bond is called its ==electronegativity==
• A ==nonpolar covalent bond== is when electrons are shared equally because two atoms have the same electronegativity
• A ==polar covalent bond== is when an atom is bonded to a more electronegative atom, the electrons will therefore not share equally

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Ionic Bonds

• Two resulting oppositely charged are called ==ions==
• Positively charged results in a ==cation==
• Negatively charged results in an ==anion==
• A ==hydrogen bond== is formed when there is a noncovalent attraction between hydrogen and an electronegative atom
• ==Van Der Waals interactions== occur when atoms get just close enough that a few electrons in their valence shell (electron cloud) touch

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Chemical reactions make and break chemical bonds

• The making and breaking of chemical bonds leading to changes in the composition of matter are called chemical reactions
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• The point at which the reactions offset one another exactly is called ==chemical equilibrium==
• The unequal sharing of electrons and water’s V-like shape make it a polar molecule.
• The phenomenon of the ==cohesion== of water molecules is due to hydrogen bonds
• ==Adhesion== is the clinging of one substance to another
• ==Surface tension== is a measure of how difficult it is to stretch or break the surface of a liquid
• Anything that moves has ==kinetic energy==
• The ==specific heat== of a substance is defined as the amount of heat that must be absorbed or lost for 1g of that substance to change its temperature by 1C
• ==The heat of vaporization== is the quantity of heat a liquid must absorb for 1g of it to be converted from the liquid to the gaseous state
• ==Evaporative cooling== occurs because the hottest molecules, (those with the greatest kinetic energy) are the ones most likely to leave as a gas

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Water: The Solvent of Life

• ==A solution== is a liquid that is a completely homogeneous mixture of two or more substances
• ==A solvent== is the dissolving agent of a solution
• ==The solute== is the dissolving agent of a solution
• ==An aqueous solution== is one in which the solute is dissolved in water, water is the solvent
• A ==hydration shell== is formed when there’s a sphere of water molecules around each dissolved ion
• Any substance that has an affinity for water is said to be ==hydrophilic==
• Substances that are nonionic and nonpolar are ==hydrophobic==
• ==Molarity== is the number of moles of solute per liter of solution
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• ==An acid== is a substance that increases the hydrogen ion concentration of a solution
• A substance that reduces the hydrogen ion concentration of a solution is called ==a base==

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Properties of water:

• Anomalous expansion of water

• High specific heat capacity (evaporative cooling and heat of vaporization)

• Hydrogen bonds (pattern when it freezes)

  

• Its versatility of it as a solvent because of the polar molecules

• Cohesion (surface tension)

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