HW #19 for 5/2

Answer on a piece of separate piece of paper:

Identify each of the following changes as chemical or physical.  If it is a physical change give the name of the change of state.  Then identify if it is an exothermic or endothermic reaction. :

1.) Solid iodine turns directly into gaseous iodine when left on your table.
2.) Solid sodium hydroxide mixes with liquid water and the mixture turns very hot.
3.) A cold pack is activated by a packet of liquid water is burst open and mixed with solid ammonium nitrate and immediately turns cold.
4.) Outside a bottle of water is left out and turns to gaseous water.
5.) Then overnight, the weather turns cold and the gaseous water forms frost on the plants outside.
6.) A cake is mixed and cooked in the oven for Mother's Day.
7.) Special sun paper is left outside in the sun and it turns to a different color.
8.) Steam collects underneath the lid of a pot and turns to water drops.

Ice Cream Lab

ICE CREAM LAB

Problem: When you make ice cream what is the purpose of the salt that is added to your ice? You will experiment different ratios with and without salt to see which is the most successful.

Pre-Lab Questions:

1. What do you think would make a “successful” ice cream in lab? What would you like your ice cream to be like before you eat it?

2. Is making ice cream a physical or chemical change? Explain why.

3. What is the change of state that is occurring when you make ice cream? Is it exothermic or endothermic? Explain why.

Make your hypothesis:

What ratio of salt to ice do you think will produce ice cream the fastest, and give the reason why you think this. 

Procedure:

1. Place 6 cups of ice in your milk jug.

2. Measure your salt on the scale as listed in your assigned ratio below. 

3. Place your salt with your ice and shake up your jug to mix it up.

4. Take your tin can to Ms. Cotta to fill with the ice cream solution.

Ratio                   Amounts

0:100                  no salt, 6 cups of ice

1:10                    40 g salt, 6 cups of ice

1:8                       50 g salt, 6 cups of ice

1:5                       80 g salt, 6 cups of ice

1:4                       100 g salt, 6 cups of ice

1:2                       200 g salt, 6 cups of ice

1:1                       400 g salt, 6 cups of ice

5. Push your tin can down into your ice and salt mixture so that it is surrounded by ice cream on the sides and underneath.

6. Put your thermometer into the ice (NOT THE ICE CREAM) and measure the initial temperature of the ice.

7. Stir your ice cream regularly with the wooden stick so that it will freeze evenly. The bottom and sides will freeze first.

8. Every five minutes check the temperature of the ice and write it in your data table.

9. Check the consistency of the ice cream and write and observation such as runny (still like milk), thin (little frozen pieces), thick (almost frozen).

10. After 30 minutes you may dish out your ice cream to you and your partner and try it out.

Data Table

Salt to Ice Ratio (write your ratio)	0 mins	5 mins	10 mins	15 mins	20 mins	25 mins	30 mins
Temperature
observation (runny, thin, thick)

Clean-Up:

1. Wash out your tin can and replace at your table.

2. Wash out your milk jug in the sink and replace at your table.

3. Wash out your bowls (IF THEY ARE PLASTIC) and recycle them in blue bin.

4. Throw out your spoons and wooden stick.

5. Wipe down your table with a sponge if needed.

Conclusion:

Use the following words to explain this experiment to someone else in a short paragraph: freezing, melting, temperature, ice cream, mixture.  Please underline each of these words in your paragraph.

Questions:

1. Why did the ice cream solution freeze? What is required to turn your liquid to a solid?

2. Which ratio makes ice cream the fastest? What is your evidence for this?

3. What is the purpose of the salt? Would this work without salt? What is your evidence?

4. What was the change of state that occurred? Is it a physical or chemical change? Why?

5. What is the variable (the thing that changes) and controls (the things that stay the same) in this experiment?

6. Draw a model showing what your ice cream mixture was like when it was first place in the ice and then a second model showing it at the end of 30 minutes. Show the speed of the molecules and explain which way the heat is flowing.

HW #18 plus extra credit opportunity

Go to this website: Science World Magazine

1) Then click on the sign in button
2) Enter this password for our class: CottaS303 (make sure to use CAPITAL letters for C and S)
3) Then look at the recent issues for the magazine for April 18, 2016 with the melting ice on the cover
4) Then click on the digital issue and read the article in that magazine entitled: "Massive Meltdown" on page 8-11.
5) After reading, look at page 9 for the box that says "Click for 4 bonus skills sheets" and click on it.
6) Go to the first page of the skills sheets entitled "Explore an Article" and answer those five questions on a separate sheet of paper.

For EXTRA CREDIT:
1) Go to the May 9, 2016 issue with octopus on the cover
2) Page 20-22 of the issue
3) Read the clues to uncover the mystery element
4) Answer what the element is and the five questions on page 22 on a separate sheet of paper

If you have problems, e-mail me: julianne.cotta@lausd.net

Study Guide for Energy Test

--Be able to explain what heat is and be able to draw a model that show the heat flow between two objects.
--Be able to explain what temperature measures and be able to draw a model
--Know how to use the formula Q=s x m x delta (triangle) T and know what each of the letters represents and MEANS
--Know what exothermic and endothermic mean and be able to distinguish in a reaction which is exo or endo by how the particles are moving (for example--melting--from solid to liquid--particles are speeding up thus need to gain energy--so it is endothermic)
--Be able to model an exothermic and endothermic reactions
--Know what the greenhouse effect is and how it works heating up the earth
--Know what are the greenhouse gases
--Know what the different types of fossil fuels are--petroleum, coal and natural gas and where they come from
--Know what are alternative energy sources such as solar, wind, nuclear

HW #17 for 4/25

Go to this website: Science World Magazine

1) Then click on the sign in button
2) Enter this password for our class: CottaS303 (make sure to use CAPITAL letters for C and S)
3) Then look at the recent issues for the magazine for April 18, 2016 with the melting ice on the cover
4) Then click on the digital issue and read the article in that magazine entitled: "Massive Meltdown" on page 8-11.
5) After reading, look at page 9 for the box that says "Click for 4 bonus skills sheets" and click on it.
6) Go to the third page of the skills sheets entitled "Heat-Trapping Gases" and answer those five questions on a separate sheet of paper.

If you have problems, e-mail me: julianne.cotta@lausd.net

Summer Opportunities

1) USC Engineering Program
Dates: July 18-29th
Deadline: May 1st
Information
Apply
Requirements: Unofficial transcript and a teacher recommendation

2) UCLA Physics and Astronomy
Dates: June 14-August 2 on Tuesday evenings from 7:30-10:30pm
Deadline: May 1st
Information
Apply

3) L.A. Sanitation Internship
Dates: June 20th to July 29th
4 hours a day paid at $10 a hour
e-mail to send application: rhonda.dowdy@lacity.org 
Requirements: Resume, letter of recommendation and transcript
Deadline: April 29th

4) FORM academy at UCLA
Dates: August 1st to 6th from 9am-4pm
e-mail to request and send an application: bdrucker@arts.ucla.edu
Deadline: May 30th

HW #16 for 4/21

Visit this website about climate change and answer the following questions:

http://climatekids.nasa.gov/menu/big-questions/

Go to the section entitled:  "What Is Global Climate Change?"
1. Explain the difference between climate and weather.
2. Explain what is our "global climate" is and the parts of our global climate.

Go to the section entitled: "What is the Greenhouse Effect?"
3. Compare how the Earth's atmosphere acts like an actual greenhouse.
4. What is the problem that increased carbon dioxide in our atmosphere is creating for the ocean? How is it changing the ocean?
5. What is the "cloud riddle" that has scientists confused?

Go to the section entitled: "How do we know the climate is changing?"
6. How many degrees is the planet warming? How many of the last twelve years have been the hottest on record?
7. How are scientists able to tell what Earth was like many years ago?

HW #15 for 4/19

HW #15 for 4/19:
1. A student performed an experiment in which a yellow solution is poured into a beaker
containing a colorless solution. A bright yellow precipitate formed, and the temperature of the
reaction container increased.
Which of the following statements is true?
A. The reaction is endothermic.
B. The formation of the precipitate is a physical change, not a chemical change.
C. The reaction is exothermic.
D. none of the above

2. The amount of heat gained or lost by a substance depends on all of the following
EXCEPT:
A. the change in temperature of the substance.
B. the change in volume of the substance.
C. the mass of the substance.
D. the specific heat capacity of the substance.

3, Which change of phase is endothermic?
A. CO₂(g) ® CO₂(s)
B. H₂O(l) ® H₂O(s)
C. I₂(s) ® I₂(g)
D. H₂O(g) ®  H₂O(l)

4. You place 100.0 g of a hot metal in 100.0 g of cold water. Which substance (metal or water)
undergoes a larger temperature change? Why is this?

5. What is the difference between “quality” and “quantity” of energy? Are both conserved? Is either
conserved?

HW #14 for 4/18

1.) A process is exothermic if:
A.) Energy flows into the system
B.) Energy flows out of the system
C.) The energy level remains constant
D.) The temperature of the system increases

2.) How many CALORIES of heat must be added to 3.0 x 102 g of water in order to raise its temperature by 40.0 degrees C? (Hint: first find Joules and then convert to calories)

3.) If the same quantity of heat is supplies to 100 g of each of the following substances, which substance will increase the most in temperature? (look at table on pg. 329): Water, iron, gold, ice, or carbon

4.) When 100 g of ice melts to form 100 g of water, the process is exothermic or endothermic? Explain why.

5.) Knowing that 1 calorie = 4.184 Joules, how many calories of energy are reguired to raise the temperature of 10.0 g of water by 1 degree Celsius?

6.) Which change results in a release of energy?
A. The melting of water
B. The boiling of water
C. The evaporation of water
D. The condensation of water

7.) Compare the amount of energy and molecules in 1 mole of water at 0 degrees Celsius and 1 mole of water at 23 degrees Celsius.
A. The amount of energy is the same and the number of molecules is the same in both
B. The amount of energy is the same, but the number of molecules is greater at 23 degrees Celsius
C. The amount of energy is greater at 23 degrees and the number of molecules is greater
D. The amount of energy is greater at 23 degrees and the number of molecules is the same

Specific Heat of a Metal Lab

Specific Heat of a Metal

Objective: To identify the specific heat of a metal and compare to the actual specific heat to our calculations.  Then to use this technique to identify an unknown metal.

Pre-Lab Questions:

1. Why do we measure the water’s volume in milliliters instead of in grams since the specific heat is in measured in J/g∙°C?

2. A 22.50 g piece of an unknown metal is heated to boiling (100°C) then transferred quickly and without cooling into 100 mL of water at 20.0°C. The final temperature of the system is 26.9°C.

a. Calculate the quantity of the heat absorbed by the water. Show all work.

b. Determine the quantity of heat lost by the piece of metal.

c. Calculate the specific heat of the metal in J/g∙°C. Show all work.

Procedure:

1.      Heat 200 mL of water to boiling. It must be rapidly boiling, if unsure ask Ms. Cotta.

2.      Meanwhile measure a sample of metal on the balance and record the mass and identity in your data.

3.      Measure 100 mL of water and place in your Styrofoam cup, record the volume and mass in your data.

4.      Record the initial temperature of the water in your data.

5.      When the water is boiling, carefully place your metal into the boiling water and leave for three minutes.

6.      After three minutes, carefully pull your metal out of the boiling water using a tool and immediately place in your prepared Styrofoam cup of water.

7.      Determine the highest temperature that the water reaches and record in your data. (MAKE SURE THERMOMETER IS TOUCHING WATER AND NOT METAL!)

8.      Make sure all the data is collected and written down.

Data for three trials:

Identity of metal:                              _________                _________                _______

Mass of metal sample:                    _____ g                      ______ g                    _____g

Volume of water used:                    _____ mL                   ______ mL                 _____mL

Mass of water used:                         _____ g                      ______ g                    _____g

Initial temperature of water:          _____ °C                    ______ °C                  _____°C

Final temperature of water:           _____ °C                    ______ °C                  _____°C

Temperature difference:                 _____ °C                    ______ °C                  _____°C

Initial temperature of metal:          _____ °C                    ______ °C                  _____°C

Final temperature of metal:           _____ °C                    ______ °C                  _____°C

Temperature difference:                 _____ °C                    ______ °C                  _____°C

Analysis:

1. Calculate the quantity of heat gained by the water like you did in your pre-lab questions for all three of your trials.

Sample 1: Q = ______J

Sample 2: Q = ______J

Sample 3: Q = ______J

2. Assume that the quantity of heat lost by the metal is equal to the quantity of the heat gained by the water. Use this quantity to determine the specific heat, s, of the metal. Use your DT for the metal from your data. 

Sample 1: _______ J/ g∙°C

Sample 2: _______ J/ g∙°C

Sample 3: _______ J/ g∙°C

3. In your calculations you assumed that all the heat from the metal went into the water. Is this a fair assumption to make? Why or why not?

4. Look at the specific heat of your metal from the white board and calculate your percent error using this equation.

% error = (actual specific heat value) – (your specific heat value calculated)        x 100%

                                                            (actual specific heat value)

HW #13 for 4/12

HW #13: 
1) Express 34.8 cal of energy in units of joules
2) Express 47.3 J of energy in units of calories
3) Determine the amount of energy as heat that is required to raise the temperature of 1000 mL of water from 25.0°C to boiling (100°C). Answer in joules and calories. 
4) If 455 J of heat is transferred to 25.0 g of water at 45.0°C, what is the final temperature of the water?

Take Home Lab #5

Take Home Lab #5:  Dissolving Energy

Question: When you dissolve household chemicals is it exothermic or endothermic?

Safety: Clean up any spills immediately. Do not consume any of the chemicals. Wash out cups well after mixing chemicals.

Materials: Cup, room temperature water, salt, borax, powdered “ultra” laundry detergent, baking soda, thermometer

Procedure: In this investigation, you are going to dissolve different common household chemicals to see if these reactions are exothermic or endothermic changes.

1. Pour ¼ cup of water in a cup. Measure the initial temperature and record in your data table.

2. Add 2 tablespoons of baking soda to the water. Mix to dissolve and find the new temperature and record in your data table.

3. Wash out the cup and start step #1 again with a clean cup of water. Record the temperature

4. Add 2 tablespoons of salt to the water and stir to dissolve, measure the temperature and record to data table.

5. Repeat these steps with “ultra” powder laundry detergent and borax.

Data Table:

Substance:	Initial temperature of water:	Final temperature of mixture:
Baking soda
Salt
“Ultra” Laundry
Borax

               

Post-Lab Questions:

1. Identify which of the experiments were exothermic and endothermic.

2. What is your evidence that the reactions were exothermic and endothermic, how do you know?

3. Make two models to show what occurred in the exothermic reaction and endothermic reaction.

4. Calculate the amount of energy released or absorbed when water and baking soda were mixed. Use the formula Q=s∙m∙DT. (Where the mass of the water is 30g, s for water is 4.18 J/g∙C and your information from your data table.

5. Calculate the amount of energy released or absorbed when water and laundry detergent were mixed. Use the same formula and information from the question above.

HW #12 for 4/11

1) HW #12: pg. 333 #2,4, pg. 338 #2, pg. 353 #22, 24, pg. 355 #60 a-c
2) Late HW due next Friday
3) Composition books due next Friday (catch up on all labs posted on blog)

Flow of Energy Lab

Flow of Energy Lab

Pre-Lab Questions:

1. Explain the difference between exothermic and endothermic. Give an example of each.

2. Show in a model how the heat will flow if a hot coffee is left on a table.  In addition, show how the molecules are moving in the coffee and in the room around it.

Make your hypothesis:  Explain what will happen if a hot liquid and a cold liquid will come in contact with each other. Make sure to explain in terms of heat flow and the movement of the molecules.

Design your experiment:

Instructions—

1. Conduct three different experiments of heat flow between a cold and hot liquid. How much liquid, the temperature of the liquids, and how the liquids interact is up to you.  You may put the liquids next to each other or put them inside each other in separate containers.

2. Measure temperature regularly by timing the experiment on your phone.

3. It is your decision for how long to carry out the experiment and when to collect data.

4. Make a data table for each experiment of the three experiments, note on the data table what equipment is used.

5. Your data should be able to be made into a graph showing the temperature over time.

Data Table:

Equipment used: (Write down all of the equipment that you used)

(Make the data table as big as you need for a long as you take measurement.)

Time:	Hot Water Temperature:	Cold Water Temperature:

Jobs:

Longest hair: Set up/Recorder

Next longest hair: Clean up/Measure hot water temperature

Next longest hair: Set up/Measure cold water temperature

Shortest hair: Clean up/Timer

Analyzing:

1. Create two graphs of your data. Each graph is a different data table and experiment. On the x-axis place the time and on the y-axis place the temperature. Use a different colored pencil for to graph the hot and cold water in your graph.

2. Did any of your experiments reach a temperature equilibrium between the hot and cold water? If it did reach equilibrium tell which ones did and explain why. If it didn’t, explain why or why not you think it will reach a temperature equilibrium.

3. Look at your data and graphs, did the type of materials you used such as glass, plastic or Styrofoam effect the temperature change? (Hint: did it change temperature faster or slower?) Explain why. 

4. Did the amount of hot or cold water have an effect on the temperature change? Explain how it affect the temperatures in your data. (Hint: look at your data to see how quickly or slowly hot or cold water changed temperature.)

HW #11 for 4/7

1) HW #11: pg. 357 #2, 4-6, 8, 11
2) Periodic Assessment tomorrow
3) Comp books due next Friday

HW #10 for 4/5

1) HW #10: pg. 356 #65
2) Periodic Assessment this week

Energy in Snacks Lab

Energy Value of Snacks

Problem: How much heat is available from the combustion of peanuts, almonds, and other snacks? Can this heat be measured?

Objective:  When you eat food, your body is actually “combusting”-burning the food.  The fat, protein and carbohydrates react with the oxygen in your body to produce carbon dioxide and water.  You will choose three types of snack to burn and measure the amount of energy released via water being heated by flame.  Unfortunately, we will lose a lot of heat to the surroundings and we also will have to heat the aluminum can as well. 

Pre-Lab Questions:

1. Look at the set up for the lab, explain which part is exothermic and which part is endothermic and tell why.

2. If a bag of potatoes weighs 5 pounds and costs $1.35.  How much does it cost per pound?

3. What if you only use 3 pounds of the potatoes and the other 2 pounds go bad. If the bag still costs $1.35 what is the cost per pound of what you actually used?

1. Hypothesis: Predict which snack of the three you are testing——will furnish the greatest amount of energy per gram. Remember that it is not about which is the heaviest but which has more amount of energy per gram. Explain your hypothesis.

2. Data Table: Make sure to write units

	Trial #1—type of nut ___________	Trial #2—type of nut _________	Trial #3—type of nut _________
Mass of snack (initial)
Mass of can
Volume of water
Temperature initial of water
Temperature final of water
Mass of leftover snack

3. Determine the change in mass of each snack from before and after combustion.

     Mass of nut (initial) – mass of leftover nut = mass of nut that combusted

4. Determine the change in temperature of water (and therefore, also the can) before and after combustion.

          Temperature final – Temperature initial = Temperature change

5. Determine the heat absorbed by the water, using the equation Q = s x m x DT

          (specific heat for water is 4.18 J/g×C°)

                                                                                                             

6. Determine the heat absorbed by the can, using the equation Q = s x m x DT

          (specific heat for aluminum is 0.9 J/g×C°)

7. Determine the total heat absorbed by the water and the can. Add #5 + #6.

          NOTE: This is also equal to the heat released by the snack.

8. Determine the total heat released per gram of nut. #7 divided by #3.

          Divide by the total heat by the total gram of nut that combusted.

9. Summary Table

	Trial #1—type of snack	Trial #2—type of snack	Trial #3—type of snack
Mass of combusted nut #3
Change in Temperature (DT) #4
Heat absorbed by the water #5
Heat absorbed by the can  #6
Total heat absorbed #7
Total heat released per gram of nut #8

10. Critique the procedure used in this experiment. Do you expect the procedure to give an accurate energy value for the nuts? Explain your answer.

11. Draw a model of the set up before it is lit and then a second model after it is lit to show the direction of the heat flow and which part is exothermic and endothermic.  Remember to draw what is happening to the molecules!