In a synthesis reaction, elements are combining to make compounds and molecules. These are the reactions that show how bonding happens.
In a decomposition reaction, molecules are breaking apart. These are the opposite of synthesis reactions.
In a single displacement reaction, one element un-bonds with an element and re-bonds with another. An element switches its bond with another reactant.
Zn + 2HCl ZnCl 2 + H 2 ++ ZnH H Cl H H
In a double displacement reaction, two elements un-bond with an element and re-bond with another. Two elements switch their bond with another reactant.
NaCl + AgF NaF + AgCl + +
In order for a chemical reaction to take place, energy must be found and used. The energy used to make a reaction happen is called activation energy. Energy used in reactions can be any form: thermal (heat), light, electric
Activation energy gives the reactants enough energy to react. Once activation energy is added to reactants, the reaction can take place. After the activation energy is used by the reactants, the products have either more or less energy than the reactants.
Sometimes the activation energy used increases the amount of energy the products have. Sometimes the activation energy used decreases the amount of energy the products have. These differences make reactions either endothermic or exothermic.
In an endothermic reaction, activation energy is absorbed or taken in during the reaction. In decomposition reactions, energy is endothermic. This is because a large amount of energy is needed to decompose (break apart) a molecule.
Energy is needed to be taken (stolen) from outside sources to help the activation energy do its job. This energy that was absorbed in the reaction is given to the products. In endothermic reactions, the energy of the products is always greater than the reactants.
Endothermic reactions take in energy and give it to the products.
How many units of energy were absorbed (stolen) from somewhere else? ENERGYENERGY TIME of REACTION Reactants Products Energy Absorbed Activation Energy
In an exothermic reaction, the activation energy is given off or lost during the reaction. In synthesis reactions, energy is exothermic. This is because the amount of energy each reactant has individually is greater than the amount that the products have.
Energy that is used as activation energy is greater than the energy needed for the products to exist. This extra energy given off (lost) from the reaction in the forms of light, thermal energy (heat), or sometimes electricity. In exothermic reactions, the energy of the reactants is always greater than the products.
Exothermic reactions give off extra energy that the reactants had.
How many units of energy were given off (lost) during the reaction? ENERGYENERGY TIME of REACTION Reactants Products Energy Given Off Activation Energy
Sometimes reactions cannot happen or happen too slowly on their own to be completed. In these situations, a catalyst used. A catalyst is a substance that is needed to stimulate the reaction.
Catalysts have 4 properties in common: 1.) They speed up a chemical reaction 2.) They are not considered a reactant 3.) Their mass is not part of the products 4.) They are not chemically affected by the actual chemical reaction
A reaction is making new products. The speed at which these new products form is called the reaction rate. Catalysts are designed to increase the rate of reactions (speed them up). There are other factors that can also increase or decrease the rate of chemical reactions.
Temperature – reactants at higher temperatures have more thermal energy and can react faster. Concentration – the higher the concentration, the greater the reaction rate.
Surface Areas – more exposed surface area of the reactants makes for faster reaction rates. Inhibitors – These are the opposite of catalysts. They slow down or stop reactions from happening.