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 + O 2 -> Fe 2 O 3 Iron Oxide

Reactants and Products Reactants -> Products C 6 H 12 O > 6CO 2 + 6H 2 O 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? C 6 H 12 O > CO 2 + H 2 O How do we balance it? C 6 H 12 O > 6CO 2 + 6H 2 O

Let’s Practice K + B 2 O 3 -> K2O + B 6K + B 2 O 3 -> 3K2O + 2B CH 4 + O 2 -> CO 2 + H 2 O CH 4 + 2O 2 -> CO 2 + 2H 2 O Al + S 8 -> Al 2 S 3 16Al + 3S 8 -> 8Al 2 S 3

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 -> 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 (H 2 O 2 ) is a harmful by- product that some of our cells give off. The enzyme catalase (shown here in the chicken liver) breaks the H 2 O 2 into H 2 O 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