Reaction Rates 8 th gr. Chemistry

Warm-up  1’s and 2’s turn and face the 3’s and 4’s  Discuss your picture in your group and pick the best picture to represent catalyst and the best picture to represent inhibitor.

 Catalyst- a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.

 Inhibitor- a substance that slows down or prevents a particular chemical reaction or other process

 Chemical reaction- a reaction happens when two or more molecules interact and something happens.molecules  A chemical change is when you start with one compound and turn it into another.  Ex- A steel garbage can rusting is a chemical reaction. That rusting happens because the iron (Fe) in the metal combines with oxygen (O 2 ) in the atmosphere.  Non-example- When a refrigerator or air conditioner cools the air, there is no reaction. That change in temperature is a physical change.

Safety  What safety precautions must we take to ensure safety?  Goggles at all times!  Aprons  Long pants and sneakers  Keep glassware away from the edge of counter or sink  Handle hot glassware with care, use beaker tongs  Do not eat or drink in the lab  PAY ATTENTION!

Part A  Independent variable- is the factor that the investigator changes.  What is the independent variable in Part A?  A: Water temperature Independent VariableReaction rate (s) Cold water Hot water

 Dependent variable- is the factor that changes because of the independent variable. The data that is collected.  What is the dependent variable in Part A?  A: Time in seconds that it takes for the tablet to dissolve

Part B  Independent variable- is the factor that the investigator changes.  What is the independent variable in Part B?  A: Surface area of tablet Independent variableReaction time (s) ¼ tablet Crushed tablet

Part B  Dependent variable- is the factor that changes because of the independent variable. The data that is collected.  What is the dependent variable in Part B?  A: Time in seconds that it takes for the tablet to dissolve

Temperature and reactions rates  Usually, an increase in temperature is accompanied by an increase in the reaction rate.  Temperature is a measure of the kinetic energy of a system, so higher temperature implies higher average kinetic energy of molecules and more collisions per unit time.

Surface area and reaction rates  The smaller the size of the solid particles, the greater the area that the reaction can take place in.  So finely divided powder reacts more quickly than the same stuff in a great big lump!

Warm-up  1’s and 2’s turn and face the 3’s and 4’s  Discuss your picture in your group and pick the best picture to represent exothermic and the best picture to represent endothermic.

 Pd 3 and Pd 4- Hand in Criss- Cross paper!

 Exothermic- reaction or process accompanied by the release of heat.

 Endothermic- a chemical reaction that requires heat in order to proceed

Safety  What safety precautions must we take to ensure safety?  Goggles at all times!  Aprons  Long pants and sneakers  Keep glassware away from the edge of counter or sink  WASH HANDS!  Do not eat or drink in the lab  PAY ATTENTION!

Part A  If I add a piece of liver to hydrogen peroxide, then there will be a __________________ reaction.

Part B  If I add baking soda to vinegar, then there will be a __________________ reaction.

 Remember to take the temperature BEFORE you put the liver in the H 2 O 2 and BEFORE you add the baking soda (Na 2 CO 3 ) to the vinegar!