What You Will Learn Extrapolation & Interpolation Exothermic & Endothermic Reactions

Why It’s Important Extrapolation & interpolation are the basis for scientific prediction. While energy diagrams can predict the behavior of chemical reactions.

The Halogens – Quiz Wednesday All of the halogens are toxic. Chlorine, bromine and iodine are used as disinfectants. They are most often found in nature as anions with a -1 charge. They are often found in compounds with the alkali metals and alkali earth metals. Fluorine Chlorine Bromine Iodine Astatine

F Cl Br I At

The Noble Gases – Quiz Wednesday The noble gases are found in nature in pure elemental form. They are most often found with no charge. Noble gases are found as monatomic gases. Radon is radioactive.

Helium Neon Argon Krypton Xenon Radon

He Ne Ar Kr Xe Rn

Quiz Wednesday Also Includes… Identifying a reaction energy diagram as either exothermic or endothermic. Using a graph to extrapolate and/or interpolate from recorded data to make predictions. Both of which we will cover today…

Electrolysis Lab Report Notebooks will be picked up at the end of class on Thursday. Pick them up again Friday at the beginning of class for the Iodine Clock lab exercise at the end of this week. Two students need to try again to pass the safety quiz before next Friday.

Bruin Pride! A Shout-Out Congratulations to all of those involved in the pep rally last week.

Review: The Electrolysis of Water Maybe next time we can blow hydrogen bubbles…

http://youtu.be/d49TzVF1gmY

Review: The Electrolysis of Water We learned several things from our lab experiment last week: •

Hydrogen gas is much different than water. Compounds are different than their constituent parts.

• •

We had to put energy in for the reaction to occur. It was possible to get the energy back by burning H2 with O2. The reaction below must be reversible.

Review: The Electrolysis of Water We also learned that chemical reactions entail the rearranging of electrons. Judging by the Lewis dots below, have the electron arrangements changed?

Reactants

Products

Energy In, Energy Out Note in the reactions below that the arrow may be reversed. This means that the reaction can go both ways.

Energy In, Energy Out In the top reaction we liberated hydrogen gas from water. In the bottom reaction we burned hydrogen gas with oxygen and turned it back into water.

Energy In, Energy Out For which reaction did we need to put energy in? For which reaction were we able to get energy out?

Exothermic & Endothermic There are two types of chemical reactions in relation to heat energy. 1. Endothermic reactions take heat from their surroundings

2. Exothermic reactions give heat to their surroundings.

Endothermic or exothermic?

Exothermic & Endothermic Reading the difference:

Endothermic or Exothermic?

http://youtu.be/w6cMmk8LZgQ

Endothermic

http://youtu.be/H5Q2jkVDzeQ

For Tomorrow Be able to distinguish which graph is which & be able to tell the difference between these reactions, pictorially.

Extrapolation & Interpolation For our experiment this Friday we will record the speed of a chemical reaction. We will record the time in seconds on the X axis & record the temperature on the Y axis in Fahrenheit.

Extrapolation & Interpolation We will need to both extrapolate & interpolate the points of data.

Interpolation & Extrapolation The predicting of what happens outside or inside actual known points of data is called interpolation and extrapolation. Interpolation – is predicting what happens between points of data. Extrapolation – is predicting what happens beyond points of data. Both are a type of prediction.

Modeling: Can Anything Go Wrong? The quality of our model is determined by the accuracy of the predictions we can make from it. Spaghetti plots are a type of extrapolation.

Predicting Behavior Are there any trends in the data below?

Predicting Behavior Could we predict what would happen at 68 F?

Predicting Behavior How precise is our prediction for 68 F? How do we find out?

Science Fiction Predictions Ten science fiction predictions that became fact…

http://youtu.be/GiMzZ8-Ebq0

Science & Graphs One area where scientists and mathematicians get along is in the area of graphing data. Mathematicians have derived the functions for almost any graph that we can conceive of.

Science & Graphs, Empiricism v. Logic Mathematicians have derived the functions for almost any graph that we can conceive of.

Cautions & Caveats We should not put too much stock into extrapolation and interpolation, however. Sometimes the data does not behave as we would predict.

Cautions & Caveats Let’s look at the growth of a population of mosquitos…

Cautions & Caveats Let’s assume that most points along this line were derived from actual data.

Cautions & Caveats What happens to the population next?

Cautions & Caveats We may assume that the population continues to grow. But what if a storm hits?

Cautions & Caveats Don’t put too much faith into extrapolation & interpolation. The best data is that which is directly recorded.

How Many Exothermic Reactions?

http://youtu.be/u6MfZbCvPCw

The Halogens – Quiz Wednesday All of the halogens are toxic. Chlorine, bromine and iodine are used as disinfectants. They are most often found in nature as anions with a -1 charge. They are often found in compounds with the alkali metals and alkali earth metals. Fluorine Chlorine Bromine Iodine Astatine

F Cl Br I At

The Noble Gases – Quiz Wednesday The noble gases are found in nature in pure elemental form. They are most often found with no charge. Noble gases are found as monatomic gases. Radon is radioactive.

Helium Neon Argon Krypton Xenon Radon

He Ne Ar Kr Xe Rn

Quiz Wednesday Also Includes… Identifying a reaction energy diagram as either exothermic or endothermic. Using a graph to extrapolate and/or interpolate from recorded data to make predictions. Both of which we will cover today…