Understanding Chemical Reaction Rates

Chemical Reactions

• A chemical reaction transforms one set of chemical substances into another, involving reactants and products.
• Reactants/reagents are the substances initially involved.
• Reactions are characterized by a chemical change, yielding products with different properties than reactants.
• The rate of a reaction varies depending on the factors involved during the reaction.

Rate of Reaction

• The Law of Conservation of Mass is applied to chemical reactions.
• Chemical reactions have evidence and expressions.
• Products of chemical reactions can be predicted.
• It is possible to distinguish the difference between reactants and products in chemical reactions.
• Types of chemical reactions can be identified.
• Reaction rate is the time or speed at which reactants convert into products.
• Reaction rate refers to the time frame or duration for a reaction to complete.
• Activation energy is the minimum energy required for a reaction to occur, without the required energy, a reaction will not take place.
• Collision Theory states that for a reaction between two particles to occur effectively, the particles must collide.

Measuring Reaction Rate

• Reactions occur when reactant molecules effectively collide, possessing minimum energy and correct orientation.
• Reaction rate is the speed at which a chemical reaction occurs; it can be quick or slow and can be altered.
• Reaction rate can be observed by monitoring the disappearance of a reactant or the appearance of a product over time.
• Chemists use two common methods to measure reaction rate: measuring the speed of product formation (indicated by color change and/or gas formation) and measuring the speed at which reactants are used up.
• Effective collisions require particles to collide with enough kinetic energy and the correct orientation to break existing bonds and form new ones.
• Collision Theory states that reactions between two particles require effective collisions between those particles.

Factors Affecting Reaction Rates Include:

• Temperature; raising the temperature increases molecular motion and collision likelihood, increasing the reaction rate. If you lower the temperature, the molecules are slower and temperatures drop which lowers there reaction rate.
• Nature of reactants.
• Physical state; reactions in heterogeneous mixtures are limited by the contact surface area between phases.
• Concentration which states that more substance in a system increases collision chances and reaction speed; less substance leads to fewer collisions and slower reactions.
• Catalyst; lower the activation energy and speed up the chemical reaction, remaining unchanged themselves.

Catalysts

• Catalysts speed up chemical reactions by lowering the activation energy without being consumed in the process.
• Factories use catalysts to make plastics and drugs with natural catalysts known as enzymes that play a role in digestion.
• Common types of catalysts are enzymes, acid-base catalysts, and surface catalysts.
• Examples of catalysts used everyday are Bakers adding vitamin C to increase the speed of gluten formation, eggs whipped in copper bowls that form a compound called copper conalbumin, adding papaya when cooking “Chicken Tinola” will help tenderize the chicken, marinating meat in pineapple juice will help tenderize the meat.