Chapter 2: The Chemistry of Life Section 1: The Nature of Matter CCS Biology Mr. Bogusch

Atoms Atoms – 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 Isotopes Elements – 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 Isotopes Isotope – 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. Uses Radiometric 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 Bonds Ionic Bond – formed when 2 or more electrons are transferred from one atom to another Ions – atoms that gain or lose an electron For example Na+ + 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 bonds For example: H2O

Chemical Bonds Van der Waals Forces – a weak chemical attraction between oppositely charged regions of nearby molecules For Example: H2O, Tokay gecko

Chapter 2: The Chemistry of Life Section 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 Molecule Polarity – 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 Molecule Hydrogen 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 water Cohesion 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 Molecule Heat 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 water Solute – the substance that is dissolved Solvent (water)– the substance in which the solute dissolves Water’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