Chapter 2: The Chemistry of LifeSection 1: The Nature of Matter

CCS BiologyMr. Bogusch

AtomsAtoms – basic units of matter

Atoms are made of three parts

Proton – positively charged subatomic particle

Neutron – subatomic particle with no charge

Electron – negatively charged subatomic particle

1/1840 mass of a proton

An atoms positive and negative charges even each other out which make the atom neutral

Atomic Models

Elements and IsotopesElements – pure substance that consist entirely of only one type of atom

Atomic number – number of protons

More than 100 elements are known and organized on the periodic table

Interactive Periodic Table of Elements

Elements and IsotopesIsotope – atom of the same element that have different number of neutrons

Mass Number – total number of protons and neutrons

Radioactive Isotope – nuclei are unstable and break down at a constant rate over time.

UsesRadiometric dating

Detect and treat cancer

Chemical Compounds

Compound – substance formed by the chemical combination of two or more elements in definite proportions

Chemical Formula Examples

NaCL, H2O

Chemical Compounds

The characteristics of compounds are usually different form the individual elements it is made of

For Example H2O – Water – if you combine hydrogen gas and oxygen gas it can be explosive!

NaCl – Salt – sodium chloride – salt is essential to all living things

Na – Sodium – silver colored metal soft enough to cut with a knife that reacts explosively with water

Cl – Chlorine – poisonous gas used in WWI – chemical warfare

Hydrogen and Oxygen Balloons

Sodium and Water

Chemical BondsIonic Bond – formed when 2 or more electrons are transferred from one atom to another

Ions – atoms that gain or lose an electron

For exampleNa+ + Cl --- NaCl

Positively charged + negatively charged = neutral charge

Ionic Bonding - NaCl

Chemical Bonds

Covalent Bond – formed when atoms share electrons

Molecule – atoms joined together by covalent bondsFor example: H2O

Chemical BondsVan der Waals Forces – a weak chemical attraction between oppositely charged regions of nearby molecules

For Example: H2O, Tokay gecko

Chapter 2: The Chemistry of LifeSection 2: Properties of Water

The Water Molecule

Found in liquid form over most of the Earth’s surface

Like most molecules, Water is neutral

H2O has 10 protons (positive) and 10 electrons (negative)

The protons and electrons balance each other out!

The Water MoleculePolarity – a molecular with an uneven distribution of charge

Oxygen has 8 protons which attract electrons strongly, as a result most of water electrons are found near the oxygen atom making that side of the atom partially negative charged

The Water MoleculeHydrogen Bonding - that attraction between a hydrogen atom with a partially positive charge with another atom with a partial negative charge

Because of their partial positive and negative charges, polar molecules can attract each other.Because water is a polar molecule, it is able to form multiple hydrogen bonds, which account for many of water’s special properties.

The Water Molecule

The Water Molecule

Cohesion –attraction between molecules of the same substance

Water can attract itself forming “beads” of waterCohesion also produces surface tension

Water molecules hydrogen bonds have a certain amount of strength

For example – spiders that can walk on water

Cohesion and Adhesion

The Water Molecule

Adhesion – the attraction between molecules of different substances

For example: water on glass

The Water MoleculeHeat Capacity

Since there are multiple hydrogen bonds between water molecules it takes a large amount of energy to cause those molecules to move fast, which raises the temperature.For example: large lakes and oceans retain heat even though the air will become colder. This protects against drastic change in temperature

Solutions and Suspensions

Mixture – a material composed of two or more elements or compounds that are physically mixed together but not chemically combined.

Solutions and Suspensions

Two types of mixtures that re combined with water are solutions and suspensions

Solutions- a substance that is evenly distributed in waterSolute – the substance that is dissolvedSolvent (water)– the substance in which the solute dissolvesWater’s polarity gives it the ability to dissolve both ionic and other polar molecules

Suspension – mixtures of water and nondissolved material

Acids, Bases, and pH

Water molecules split to form ions

pH Scale – indicates the concentration of H+ ions in a solution

Range 0 – 14 Acids < pH of 7 (contain a high concentration of H+ ions)Bases > pH of 7 ( contain a high concentration of OH- ions and a low concentration of H+ ions)Neutral = 7 (contain no H+ ions or OH- ions “theoretically”)

Acids, Bases, and pH