9/29/30

Tape in Your

Warm up and

Complete

Justify Your

Answer Choice:

I -STARTER: Warm up

about elements.

III- APPLICATION

IV –CONNECTIONS:

10/18/11

Justify Your

Answer Choice:

II- PRACTICE: Prelab Notes

III- APPLICATION

IV –CONNECTIONS:

V -EXIT: 3-5 Summary Sentences

I: StarterTurn to your next blank page and write the date at the top. 10-18-11Tape your warm up directly underneath and complete!

Justify you r answer out to the side of your warm up.

II: PracticeWater or Not???

Please take notes in this section to prepare for the lab we will be completing in today’s application section.?

Let’s do a quick review…

What is a element?Pure substance that can not be chemically broken down

What is a compound?2 or more atoms chemically combined that cannot be

physically pulled apart

Are Elements found on the Periodic Table?Yes

Are Compounds found on the Periodic Table?No.

What is a physical change?Rearranges molecules but doesn’t affect their internal

structures. Some examples:

1) Whipping egg whites – air is forced into the fluid, but no new substance is produced!

2) Sugar dissolving in water – sugar molecules are spread within the water, but

the individual sugar molecules are unchanged

3) Boiling water –water molecules are forced away from each other

when the liquid changes to vapor, but molecules are still H2O

4) Dicing potatoes – cutting usually separates molecules without

changing them.

What is a chemical change?Any change that results in the formation of new chemical substances. Atthe molecular level, chemical change involves the making or breaking of bonds between atoms. These changes are chemical:

1) Iron rusting – Iron oxide forms through the reaction of iron and oxygen in

the presence of water or air moisture.

2) Gasoline burning – when gasoline is burned in car engines,

water vapor and carbon dioxide form.

3) Bread rising – Yeast changes carbohydrates into carbon

dioxide gas.

4) Milk souring – When bacteria use the lactose sugars in milk they change

the sugar and sour-tasting lactic acid is produced.

SIGNS OF CHEMICAL CHANGE (How can you tell?)

– Gas Formation – a gas is formed & released as the reaction is completing (NOT the same as boiling)

– Solid formation (precipitate) – a solid “rains down” to the bottom of the container, may be suspended in a cloudy solution

– Temperature Change – It takes energy to break chemical bonds. Energy is released (heat) OR energy is absorbed (cold).

– Color Change – Not the same as mixing colors.– Light is given off– Change in smell (or taste)

Last week we looked at 2 liquids that appeared to be identical:

H2O H2O2water Hydrogen peroxide

Water• It’s chemical formula is H2O

• It is drinkable.• May be used to clean wounds.

– What happens when water is put on a wound?

What do we know about these 2 compounds so far?

Hydrogen Peroxide• It’s chemical formula is H2O2

• In its pure form could be fatal swallowed!!

• Antiseptic that is an effective way to clean wounds.– What happens when Hydrogen Peroxide is

put on a cut?• It causes bubbles

–What are these bubbles a sign of?»A Chemical Reaction

Details of how Hydrogen Peroxide works

• Hydrogen Peroxide is 3% H2O2 and 97% water

• Blood cells contain an enzyme called catalase– When you get a cut or scrape both blood and

damaged cells release catalase

• When H2O2 comes into contact with catalase a chemical reaction occurs

2H2O2 + catalase 2 H2O + O2

– The reaction causes the peroxide to turn into pure oxygen

• Bubbles are the release of the extra oxygen gas

Details of how Hydrogen Peroxide works

III: Application• For today’s application we are going to be

working in groups to figure out

Water or Not???• Your group will receive 2 cups of clear liquid

• We CAN NOT test on humans in this class!– No drinking the liquids– No putting the liquids on any body parts

So how can we test to see if the liquids are

H2O or H2O2 ???

With a potato

III: Application• Draw the set up that has been passed out to each group showing both cups of liquid

• Gently place one slice of potato into cup A– Observe and draw/label reaction

• Repeat for cup B

• You should label as appropriate in each picture:– Potato– Hydrogen Peroxide– Water– Oxygen Bubbles

Clean Up

When done carefully remove potato slice with plastic spoon, place in paper towel, and dispose in trash.

Return cups with remaining liquid and supplies as provided to you at beginning of experiment.

IV: ConnectionsDescribe why it is important to clean cuts with hydrogen peroxide a couple of times a day for several days after injury?

V: ExitSummarize what you have learned during this lesson. (3-4 sentences, please!)