Chemical Reactions

6.2

Chemical Reactions allow living things to grow, develop, reproduce, and adapt

Is this a chemical reaction?

What makes it a chemical reaction?

• Atoms or groups of atoms in substances are reorganized into different substances.

• Fe + O2 -> Fe2O3

• Iron Oxide

Reactants and Products

• Reactants -> Products

• C6H12O6 + 602 -> 6CO2 + 6H2O

• What biological process does this chemical equation explain?

Why do we have to balance equations?

• Conservation of Mass- Matter cannot be created or destroyed.

• The amount you put in is the amount you should get out.

• We use coefficients to balance equations

Is this equation balanced?

• C6H12O6 + 02 -> CO2 + H2O

• How do we balance it?

• C6H12O6 + 602 -> 6CO2 + 6H2O

Let’s Practice

• K + B2O3 -> K2O + B

• 6K + B2O3 -> 3K2O + 2B • CH4 + O2 -> CO2 + H2O

• CH4 + 2O2 -> CO2 + 2H2O

• Al + S8 -> Al2S3

• 16Al + 3S8 -> 8Al2S3

How do we get reactions started?

• Activation Energy!

• Minimum amount of energy needed from reactants to form products in chemical reactions.

Endothermic vs. Exothermic

Endothermic vs. Exothermic

Endothermic vs. Exothermic

• Endothermic -> Energy of products is higher than the energy of the reactants

• Exothermic -> Energy of the products is lower than the reactants.

Enzymes

• Enzymes are catalyst• Catalyst lowers the activation energy

• A Catalyst doesn’t increase the amount of product or get used up in the reaction

• Enzymes are biological catalyst

Chicken Liver and Peroxide

• Hydrogen peroxide (H2O2) is a harmful by- product that some of our cells give off.

• The enzyme catalase (shown here in the chicken liver) breaks the H2O2 into H2O and O.

• After the reaction is complete we can pour more peroxide onto the livers and the reaction will happen again because enzymes are not used up.

Endothermic and Exothermic

Endothermic Reactions • Photosynthesis • Water evaporation• Emergency Cold

Packs

Exothermic Reactions• Burning a Candle• Combustion of fuels• Nuclear Fission

• Draw a graph of an endothermic reaction.• Draw a graph of an exothermic reaction.

• Chemical reactions need ________ to begin.• A __________ lowers the activation energy in

chemical reactions.• A _________ is a biological catalyst.• What type of electron is available to form

bonds? __________

• Two or more elements joined in a definite amount is called ___________.

• What is the atomic number for an element composed of?

• Carbon-14 is considered a what?

• Is salt water a homogeneous or heterogeneous mixture?

• Give an example of a suspension.

• Give an example of a monomer.• Why is phosphorus important?• What 3 elements compose

carbohydrates?• Lipids are hydrophobic or hydrophilic?• What are the two types of nucleic

acids?• What are proteins composed of?

How an Enzyme works

• The substrates (reactants) bind to the active sites on the enzyme.

• Active site changes and the enzyme- substrate complex is formed.

• Substrates (reactants) react to form products• Enzyme releases the product.

Important things to remember

• Enzymes are not used up in a chemical reaction.

• An enzyme’s name describes what it does.• The active site and substrates have

complementary shapes. Think lock and key model

• pH and temperature can affect enzymes