1. Topic 8 – Reaction Rate Science 9 - Chemistry

2. Chemical Reactions involving oxygen 1. COMBUSTION - oxygen reacts with a substance to from a new substance and give off energy Ex. Fire

3. What products are produced in combustion?  CH 4(g) + 2 O 2(g)  CO 2(g) + 2 H 2 O (g)  Methane + oxygen  carbon dioxide + water

4. 2. CORROSION – slow chemical change when oxygen in air reacts with metal Ex. Rust 4 Fe (s) + 3 O 2(g)  2 Fe 2 O 3(s) Iron + oxygen  iron oxide

5. How do we protect against rust?  Galvanizing – Coating metals with thin layers of zinc –Zinc takes longer to rust than most metals!  Painting  Sacrificial metal

6. PBS Nova – Smart Bridges  https://www.youtube.com/watch?v=8qcREJ 2NsOQ https://www.youtube.com/watch?v=8qcREJ 2NsOQ https://www.youtube.com/watch?v=8qcREJ 2NsOQ

7. 3. CELLULAR RESPIRATION – chemical reaction that takes place in your body cells. C 6 H 12 O 6 + O 2  CO 2 + H 2 O + energy

8. Factors Affecting Rates of Chemical Reactions  Many factors can affect chemical reactions  One thing that must be controlled is the rate at which a reaction occurs (also known as reaction rate (RR)). REACTION RATE (RR) – the speed at which reactants are converted to products during a chemical reaction.

9. 1. Changing Temperature Temp = RRTemp = RR 2. Stirring the Reactants Adding movement energy and speed of atoms / molecules = collisions between atoms = RR

10. 3. Increasing Surface Area – Thethe surface area the more chance the reaction has to occur (smaller pieces) = RR 4. Catalysts – A substance that RR without being changed itself Ex. Enzyme (natural catalyst) – made by living things

11. 5. Changing Concentrations – number of particles (atoms or molecules) per unit of volume changes RR – # of particles / unit of volume = RR Ex. 18 mol/L H 2 SO 4 (aq) vs. 5 mol/L H 2 SO 4 (aq) WHICH IS MORE CONCENTRATED? WHICH WOULD REACT QUICKER?