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!

HW #9 for 4/4

1) HW #9 pg. 354 #36-40
2) Finish calculations for energy in snacks lab