Day 77-78 Cell Review

End of 2nd Quarter (a little early) only 96 school days to go...  It's also the start of Winter Break. 

When we return we will start Cycles of Life: Photosynthesis, Respiration and the Carbon Cycle. 

To review - Watch Brain Pop Cell Structures or Study Jams Plant Cell & Animal Cell



Generation Genius: Plant and Animal Cells is also a good resource.  *May require a subscription

Play Cell Organelle Memory:

Comparing Plant and Animal Cells Cut and Paste Activity.

Next: Photosynthesis...

69-76 Testing (and ice cream)

I know... a lot of days spent getting ready for testing and testing :(

I made a game for students using sample questions from the textbook and previous tests.

We did get to do an Ice Cream (Mixtures and Solutions) Lab with all of the 8th grade Science classes which was very fun!

Our recipe (for each lab group of 4 students):
2 cups whole milk
4 tablespoons sugar
1 teaspoon vanilla
1 quart freezer zipper bag
1 gallon freezer zipper bag
1/2 cup ice cream (course) salt
ice

Procedure
1. mix the 1st 3 ingredients in the quart bag and seal
2. put the quart bag in the gallon bag
3. add salt and ice and seal
4. shake bag back and forth for about 10 minutes or until the mixture has turned from liquid to solid
5. discard the gallon bag of ice and salt

Discussion
1. Define & Identify the solutes and solvent
2. Is the ice cream a solution, suspension or colloid?  Explain each of these terms and describe the particle size in each.

Students bring in toppings to share.

67-68 Rates of Reaction

I use the following demos to introduce students to factors that affect the rate of a chemical reaction:

1. Elephant toothpaste (concentration & catalyst)

2. Glow Stick Demo (temperature)

They make Frayer models on Endo/Exothermic reactions and answer questions about how each of the factors will affect a reaction.

Next: Semester Exams, Periodic Table T-Shirt Pictures & Ice Cream (Solubility) Lab

65-66 Endothermic and Exothermic Reactions

"Baggie Lab"

1. I write the formulas for these products on the board and ask students to count and label the elements, then make observations about their bags (color, amount etc.).

CaCl₂ and NaHCO₃

A - 3 tsp  NaHCO₃ and1tsp CaCl₂ (Endothermic)
B - 3tsp CaCl₂ and1tsp NaHCO₃ (Exothermic)

 2. Add 20 mL of water and seal with out any air, shake to combine. *Optional - add 3 drops of phenol red to show a color change acid/base)

3. Make observations.  Students should describe how they know a change has taken place and what kind (endo/exo) using evidence.

4. Compare Bag A to Bag B

5. Write a conclusion using the following "Sentence Starter"

 

Baggie Lab Conclusion

Our group had Bag___.

The procedures of the lab were____________________.

We had different results from the groups who had Bag__ because____.

A________change occurred.  We know this because we observed the following evidence_____.  It was a ______________ reaction because energy was _____________.



63-64 More on Physical and Chemical Changes

Great demos for evidence of a change (color change, precipitate, formation of a gas, change in temperature)

1. Making a gold penny (color change)



plain penny, penny soaked in zinc and NaOH, brass penny

•  Put 20 mL of NaOH (Sodium Hydroxide) and a couple zinc pieces in a 250 mL beaker on a hotplate, simmer - don't boil
• Add pennies, heat until they turn a "silver color" *I start these in the morning and pull a couple out each period, I have left them in over night - no problem
• Take penny out and rinse with water
• Heat over a flame source (alcohol, Bunsen or butane lab burner) about 3 seconds each side until it turns "gold" *careful - pennies melt!

Students will think this is magic, explain it is a mixture of 2 metals (alloy) copper and zinc which makes brass

2. Burning Magnesium (light and heat produced)

Magnesium Ribbon

3. Flame test (color change)

Use a wood splint (popsicle stick) soaked in water to burn metallic compounds
Sodium chloride (NaCl) Calcium chloride (CaCl₂) Potassium chloride (KCl) Copper chloride (CuCl₂) Strontium chloride (SrCl₂)

4. Mixing Vinegar & Baking Soda (formation of a gas, change in temperature)

5. Mixing Epsom salt & Sodium carbonate Solutions video, procedure (precipitate)