The Chemical Basis of Life - Study Guide PDF

**The Chemical Basis of Life** **Matter, Mass, and Weight** - **Matter** **-** Anything that occupies space and has mass (solid, liquid, or gas) - **Mass** **-** Amount of matter in an object - **Weight** **-** Gravitational force acting on an object of a given mass **Elements and Atom...

**The Chemical Basis of Life** **Matter, Mass, and Weight** - **Matter** **-** Anything that occupies space and has mass (solid, liquid, or gas) - **Mass** **-** Amount of matter in an object - **Weight** **-** Gravitational force acting on an object of a given mass **Elements and Atoms** - **Element** **-** simplest type of matter having unique chemical properties \- Ex. C, H, O, N, Ca, K, Na, Cl - **Atom** **-** smallest particle of an element that has the chemical characteristics of that element **Atomic Structure** 1\. Atoms consist of neutrons, positively charged protons, and negatively charged electrons. 2\. An atom is electrically neutral because the number of protons equals the number of electrons. 3\. Protons and neutrons are in the nucleus, and electrons can be represented by an electron cloud around the nucleus. - **Atomic Number** **-** number of protons in each atom of an element **-** also the number of electrons (since the number of electrons and number of protons are equal) - **Mass Number** **-** number of protons and neutrons in each atom \- e.g. Mass number of carbon (12) consisting of 6 protons and 6 neutrons **Chemical Bonds** - **What is it?** **-** occurs when outermost electrons are transferred or shared between atoms - **Types** - Ionic binding - Covalent bonding **Ionic Bonding** - **Ions** **-** are electrically charged particles formed when atoms lose or gain electrons **-** Ex. Na^+^ - **Ionic bonding** **-** results when electrons are transferred between atoms, creating oppositely charged ions \- attraction between two oppositely charged ions \- e.g. Na^+^ and Cl^-^ are held together to form sodium chloride (NaCl), or table salt **Covalent Bonding** - Formed when atoms share one or more pairs of electrons - Resulting combination of atoms is called **molecule** - e.g. covalent bond between 2 Hydrogen atoms to form a Hydrogen molecule - **Single covalent bond** - Sharing of one pair of electrons by two atoms - Indicated by a single line between the symbols of the atoms (H-H) - **Double covalent bond** - Sharing of two pairs of electrons by two atoms - e.g. carbon atom combines with two oxygen atoms to form carbon dioxide - Indicated by a double line between the atoms (O═C═O) - **Polar covalent bond** - Unequal, asymmetrical sharing of electrons between two atoms - Molecules with asymmetrical electrical charge are called **polar molecules** - e.g. two hydrogen atoms can share their electrons with an oxygen atom (H~2~O) - **Nonpolar covalent bond** - Equal sharing of electrons between two atoms - Molecules with a symmetrical electrical charge are called **nonpolar molecules** **Hydrogen Bonds** - Polar molecules have a positive end and a negative end - Hydrogen bond forms when positive end of one polar molecule is weakly attracted to negative end of another polar molecule - The attraction between molecules is much weaker than in ionic or covalent bonds - ***Dissociation*** \- the separation of ions in an ionic compound by polar water molecules. \- when ionic compounds dissolve in water, their ions **dissociate**, or separate, from each other because the positively charged ions are attracted to the negative ends of the water molecules, and the negatively charged ions are attracted to the positive ends of the water molecules. \- these dissociated ions are sometimes called ***electrolytes*** Sodium chloride (table salt) dissociates in water. The positively charged Na+ are attracted to the negatively charged oxygen (*red)* end of the water molecule, and the negatively charged Cl− are attracted to the positively charged hydrogen (*blue)* end of the water molecule. **Chemical Reactions** - **What are they?** \- the change of a substance into a new one that has a different *chemical* identity. - **Reactants** **-** substances that are altered or incorporated into another substance in a chemical reaction - **Products** **-** substances resulting from the chemical reaction **A + B → C + D** Reactants Product **Classification of Chemical Reactions** - **Synthesis reactions** **-** two or more reactants combine to form a larger, more complex product \- **e.g. A + B → AB** **ADP + P → ATP** - **Decomposition reactions** **-** reactants are broken down into smaller, less complex products **- e.g. AB → A + B** **ATP → ADP + P** - **Exchange reactions** \- combination of a decomposition reaction and a synthesis reaction **-** in decomposition, reactants are broken down. \- in synthesis, the products of the decomposition reaction are combined **- e.g. AB + CD → AC + BD** **HCl + NaOH → NaCl + H~2~O** - **Reversible reactions** \- a chemical reaction that can proceed from reactants to products and from products to reactants \- when the rate of product formation is equal to the rate of reactant formation, the reaction is said to be at **equilibrium** \- at **equilibrium**, the amount of the reactants relative to the amount of products remains constant. \- indicated by two arrows pointing in opposite directions **- e.g. CO~2~ + H~2~O H^+^ + HCO~3~^-^** **Energy** - **What is it?** \- the capacity to do work - **Subdivided into:** **Potential energy --** stored energy that could do work but is not doing so **Kinetic energy** -- does work by causing the movement of an object - **Chemical energy** \- a form of potential energy stored in the bonds of chemical compounds (atoms and molecules). It is released in a chemical reaction, often producing heat as a by-product (exothermic reaction). Batteries, biomass, petroleum, natural gas, and coal are examples of stored chemical energy. **-** e.g. breakdown of ATP **ATP** - **What does it stand for?** adenosine triphosphate - **What is it?** often called the energy currency of cells because it is capable of both storing and providing energy - When ATP is broken down (ATP → ADP + P) energy is released. **Rate of Chemical Reactions** - The rate of a chemical reaction increases when 1. the concentration of the reactants increases 2. the temperature increases 3. catalyst is present - A catalyst (enzyme) increases the rate of a chemical reaction without being altered permanently