Chapter 2 - Chemistry of Life Section 1 – Composition of Matter Section 2 – Energy Section 3 – Water and Solutions

Objectives Define the term matter Explain the relationship between elements and atoms. Explain the relationship between enzymes and activation energy. Describe the structure of a water molecule. Explain how water’s polar nature affects its ability to dissolve substances. Differentiate between acids and bases.

Composition of Matter Matter is anything that takes up space and has mass. Mass is the measure of the amount of matter that an object contains. Atom is the basic building block of matter Composed of electrons, protons, and neutrons. Protons and neutrons are found in the nucleus Electrons move about the nucleus in orbitals or electron clouds.

Atom

Elements Elements are substances that cannot be broken down chemically into simpler kinds of matter. 118 elements arranged on the periodic table Isotopes are atoms of the same element that differ in their number of neutrons.

Compounds Compounds are a chemical combination of two or more elements. Held together by bonds Ionic bonds result from electron transfer Covalent bonds result from electron sharing 8 is a magic number (2 in the case of small elements) Two type of compounds Ionic compounds Covalent compounds

Section 2 – Energy Objectives Describe the physical properties of each state of matter. Describe the role of reactants and products in a chemical reaction. Explain the relationship between enzymes and activation energy. Explain how oxidation and reduction reactions are linked.

Energy Energy is the capacity to do work

States of Matter Three common states of matter: Fourth type: Solid Liquid Gas Fourth type: Plasma: an ionized gas

Solid Solid- a substance in which the particles occupy fixed positions in a well-defined, three-dimensional arrangement. Definite shape and volume. Examples: Iron Ice

Liquid Liquid - a flowing substance with a definite volume but an indefinite shape. Definite volume and takes shape of container Examples: Water Mercury Bromine

Gas Gas – a flowing, compressible substance with no definite shape or volume. Takes shape and volume of container Examples Oxygen Hydrogen Helium

Chemical Reactions Chemical reaction occurs when one or more substances change into new substances Reactants – starting substances in a chemical reaction. Products – the ending substances in a chemical reaction.

Activation Energy Activation energy is the amount energy required in order for a reaction to take place. Catalysts speed of chemical reactions by lowering the activation energy. Enzymes are biological catalysts Without them the chemical reactions in the body would occur so slowly we would not survive.

Oxidation-Reduction Reactions Redox reaction (Oxidation-Reduction Reaction) –electrons transfer from one atom to another. Oxidation Reaction – a reactant loses one or more electrons = positive ion Reduction – a reactant gains one or more electrons = negative ions

Section 3- Water and Solutions Objectives Describe the structure of a water molecule. Explain how water’s polar nature affects its ability to dissolve substances. Outline the relationship between hydrogen bonding and the different properties of water. Identify the roles of solutes and solvents in solutions. Differentiate between acids and bases.

Importance and Properties of Water Molecular Shape and Properties A water molecule is composed of two hydrogen atoms and one oxygen atom (H2O). The oxygen end of the molecule carries a negative charge and the hydrogen end of the molecule carries a positive charge.

Shape of water The bent shape of the water molecule gives a partial negative charge around the oxygen area, and a partial positive charge around the hydrogen atoms. With both partial positive and negative charges being present on the molecule, both positive and negative charges are attracted to it.

Polarity The polar nature of water allows it to dissolve many different substances. Polarity due to an unevenly distributed charge on the molecule. Due to its molecular structure, water is a polar substance. Therefore, it can dissolve many ionic substances, such as salt, and polar substances, such as sugar. As a result of the solvent properties of water, the liquid always contains dissolved materials, particularly ionic substances. Water is known as the universal solvent because it dissolves such a large number of substances. More substances are soluble in water than in any other liquid. Water's ability to dissolve so many substances is due to its polar nature.

Polarity of Water

Hydrogen Bonding Hydrogen bond is the force of attraction between a hydrogen molecule with a partial positive charge and between another atom or molecule with a partial or full negative charge. Hydrogen bonds in water exert an attractive force strong enough so that water “clings” to itself and some other substances. Hydrogen bonds form, break, and reform with great frequency.

Cohesion and Adhesion Cohesion attractive force that holds molecules of a single substance together. Water molecules move upward through the roots of plants. Adhesion – attractive force between two particles of different substances, such as water molecules and glass molecules. Capillarity – attraction between molecules that results in the rise of the surface of a liquid when in contact with a solid.

Cohesion and Adhesion

Temperature Moderation Water has a high heat capacity, which means that water can absorb or release large amounts of energy. Keeps it cool during the day be absorbing heat and warm at night by radiating it off at night.

Solutions Solvent – the dissolving agent Solute – the thing begin dissolved Aqueous solution – solutions in which the solvent is water

Acids and Bases Hydronium ions are greater than the number of hydroxide ions – Acid Hydroxide ions are greater than the number of hydronium ions - Base

pH Scale

Buffers Buffers are chemical substances that neutralize small amounts of either an acid or a base. Buffers help us to maintain the pH values in a normal healthy body