Presentation on theme: "Chemical Reactions And Enzymes. A chemical reaction is a process that changes, or transforms, one set of chemicals into another. Mass and energy are conserved."— Presentation transcript:
A chemical reaction is a process that changes, or transforms, one set of chemicals into another. Mass and energy are conserved Reactants become products Always involve changes in the chemical bonds that join the atoms of the compounds
Because atoms are neither created nor destroyed in a reaction, a chemical equation must have an equal number of atoms of each element on each side of the arrow (i.e. the equation is said to be 'balanced').
Steps involved in writing a 'balanced' equation for a chemical reaction: 1. Experimentally determine reactants and products 2. Write 'un-balanced' equation using formulas of reactants and products 3. Write 'balanced' equation by determining coefficients that provide equal numbers of each type of atom on each side of the equation (generally, whole number values)
Note! Subscripts should never be changed when trying to balance a chemical equation. Changing a subscript changes the actual identity of a product or reactant. Balancing a chemical equation only involves changing the relative amounts of each product or reactant.
6CO 2 +__H 2 O C 6 H 12 O 6 + __O 2 6 carbons in glucose on the right means you need 6 on the left so place the coefficient 6 in front of the carbon dioxide
6CO 2 + 6H 2 O C 6 H 12 O 6 + __O 2 12 hydrogen in the glucose on the right means you must have 12 on the left. Since the hydrogen in water occurs in pairs, you will need 6 pairs to equal 12.
6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 There are 18 oxygen atoms in the reactants on the left (12 in carbon dioxide and 6 in water) so you need 18 on the right. There are already 6 present in the glucose so you will need 6 pair (12) of the oxygen
6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 This is a balanced equation!
Energy Exothermic reactions (release energy) occur spontaneously and give off heat, light, and/or sound energy Endothermic reactions (absorb energy) need a source of energy and store it in the bonds Organisms get energy from nutrients
Activation Energy energy that must be added to get a reaction started, which is recovered as the reaction proceeds difference in energy between reactants and products energy that is lost as heat free energy equal to the entropy times the absolute temperature