+ Chemical vs Physical Changes

+ Goals Define chemical and physical changes Contrast chemical and physical changes Give examples of chemical and physical changes When an interaction is described, determine if a physical or chemical change has occurred.

+ Activate Watch a film made by students defining physical and chemical changes. Using the video as a resource, write your own definition of physical changes and chemical changes.

+ Goal Determine whether a physical or chemical change has occurred.

+ Ice melts and becomes water.

+ A car rusts when iron oxidizes.

+ Salt is dissolved in a glass of water.

+ Ingredients are combined and then heated to make a cake.

+ The reaction of baking soda and vinegar produces CO2.

+ Wood burns in a fire.

+ Toast burns in a toaster.

+ Ingredients are combined to make slime.

+ Use these criteria to decide if chemical or physical changes have occurred.

+ A Mystery Reaction Students will use knowledge gained during reactions mini- unit to determine which reactions are occurring when observing a reaction and given a stoiciometric formula..

+ Vocabulary Chemical Indicator- A substance that shows changes in chemicals during a reaction. In our investigation, we will use a substance that shows changes in pH (acidity and alkalinity) by changing colors.

+ A more complex chemical reaction. We will mix 3 chemicals and a chemical indicator in a closed system. Your lab report says that we are using powdered sugar, cross this chemical out- we will not be using it. We will observe all changes that occur during the reaction. We will record our observations. We will determine which products were created during the reaction. We will hypothesize the which reaction(s) occurred to create the new products.

+ The Chemical Reaction

+ An Equation for the Reaction 2NaHCO 3 + CaCl 2 + H2O----> CaCO 3 + 2NaCl + H 2 O + CO 2 Conclusions: What new products were created during this reaction? What changes occurred during the reaction? Can you infer the kind(s) of reaction(s) that occurred?

+ C.W.A. Part 2 Students will support a claim by citing evidence and using scientific reasoning. Students will refute an incorrect claim.

+ Characteristics of Chemical Reactions…. The following are characteristics of chemical reactions. __________ 1. New products are created. __________ 2. More complex products are created. __________ 3. Atoms change places to form new compounds. __________ 4. Can create gases or precipitates. __________ 5. Combustion occurs. __________6. Change in color. __________7. The change cannot be reversed. Worksheet: Characteristics of Reactions Worksheet: Characteristics of Reactions

+ C.W.A 2- This time it’s chemicals.. We recently observed a chemical reaction. I performed the same investigation with several celebrities and asked them, in their opinion, what kind of chemical reaction occurred. Here are their answers…..

+ Mr. T: It’s a Chemical Reaction “Fool, this is an obvious example of a chemical reaction!” The temperature changed! That only happens when there’s a chemical reaction!

+ Fat Albert: Not a chemical reaction. “Hey, hey, hey!” Temperature changes aren’t proof of a chemical reaction! Temperature changes cause physical changes. For example, heating a liquid makes it evaporate.

+ Mike Tyson: Synthesis “Seriously guys. This is a physical reaction! A liquid became a gas, suckah!”

+ Randy Moss: Chemical Reaction “I think that it’s a chemical reaction. A gas was created by mixing 2 solids and a liquid.

+ Pick a Claim…. Who do you think is right? What kind(s) of reactions occurred during this experiment? Do you disagree with anyone’s claim? Can you explain to them why their claim is not correct?

+ Part 1: Temperature Change Chemical vs. Physical Reactions Decide if you agree with Mr. T or Fat Albert. What is their claim? Why do you agree? Explain to the other person why their claim is incorrect.

+ Part 2: Production of a Gas Chemical vs. Physical Reactions Do you agree with Mike Tyson or with Randy Moss? State the claim that you agree with and why you agree with the claim. If you disagree with a claim, say why you disagree.

+ Reading Resources Middle School Chemistry Chemical Change UnitChemistry Chemical Change Unit Ehow Characteristics of Chemical ChangesCharacteristics of Chemical Changes Types of Reactions from Internet Science RoomInternet Science Room

+

+ CWA Vocab Practice

+ Claim, Evidence, and Reasoning.. In a scientific paper, we use a process that is similar to the scientific method. That is, we make a claim (similar to a hypothesis,) make an observation (similar to an observation,) and draw conclusions (say how our evidence supports or does not support our claim) In a scientific paper, we use a process that is similar to the scientific method. That is, we make a claim (similar to a hypothesis,) make an observation (similar to an observation,) and draw conclusions (say how our evidence supports or does not support our claim)

+ Examples of Claims Claim: People who die in horror movies are always doing something stupid. If this is the claim that I chose, what are three pieces of evidence that I can use to back up the claim?

+ Evidence

+ Reasoning (a little tougher) Reasoning says why the evidence supports the claim

+ Relate to the C.W.A. Let’s talk about the synthesis reaction we observed with lime water (CaOH + CO2 => CaCO2 + H2O) Claim: I believe that this is an example of a _____________ reaction.

+ Evidence What happened during the reaction?

+ Reasoning: Why does the evidence support the claim? What are the characteristics of synthesis reactions? Detail the characteristics in your example.

+ Put it all together… I agree with the claim that the reaction of calcium hydroxide and carbon dioxide is an example of a synthesis reaction. During this reaction, we observed a precipitate forming and falling to the bottom of the solution when we exhaled CO2 into the CaOH solution. Our teacher told us that the products formed during this reaction were CaCO2 and H2O. During synthesis reactions, compounds join together to form new, usually more complex products. In this example, the new product was a solid- chalk. Synthesis means “coming together.” In this example the CO2 we placed in the solution joined with the calcium in the solution. Another example………