Energy Changes Lab

Energy Changes Lab                                                

Procedure:

1.  GOGGLES MUST BE WORN AT ALL TIMES UNTIL EVERYONE HAS CLEANED UP!

2. Measure the designated amount of liquid and record the temperature of liquid in the graduated cylinder with the thermometer.

3. When not using the thermometer AND stirrer place on your paper towel and not on the table.

4. Stir together your two chemicals into the Styrofoam cup and record the temperature after mixing.

5. Dump your chemicals in the large beaker in the fume hood. Wash out your Styrofoam cup, thermometer and stirrer in the sink.

6. When measuring solid chemicals make sure to use your weighing dish and zero out your scale.

7. Carefully stir your water into your solid chemicals and always replace stirrer on the paper towel.

8. Make sure that your lab table when you are finished looks the same as it began.

9. ALERT MS. COTTA TO ANY SPILLS OR BROKEN EQUIPMENT IMMEDIATELY!

Part 1:

Reaction between HCl and NaOH Data Table

Volume of 1.0 M HCl  in mL (close to 15 mL as possible)
Volume of 1.0 M NaOH in ML (close to 15 mL as possible)
Temperature of HCl before mixing (C⁰)
Temperature of NaOH before mixing (C⁰)
Temperature of mixture of HCl and NaOH (C⁰)

Part 2:

Reaction between NH₄NO₃ and H₂O

Mass of NH4NO3 (close to 8 g as possible)
Volume of H2O in ML (close to 15 mL as possible)
Temperature of H2O before mixing (C⁰)
Temperature of mixture  (C⁰)

Part 3:

Reaction between NaOH and H₂O

Mass of NaOH (close to 8 g as possible)
Volume of H2O (as close to 50 mL as possible)
Temperature of H2O before mixing (C⁰)
Temperature of mixture  (C⁰)

Part 1:  Reaction between HCl and NaOH Data Table

Temperature of mixture (C⁰): 

Temperature of HCl before mixing:          

Difference between two temperatures:  

Increase or decrease in temperature ?:                            Exothermic or endothermic ?:

Part 2:  Reaction between NH₄NO₃ and H₂O Data Table

Temperature of mixture (C⁰): 

Temperature of H₂O before mixing:         

Difference between two temperatures:                          

Increase or decrease in temperature ?:                            Exothermic or endothermic ?:

Part 3:  Reaction between NaOH and H₂O Data Table

Temperature of mixture (C⁰): 

Temperature of H₂O before mixing:         

Difference between two temperatures:                          

Increase or decrease in temperature ?:                            Exothermic or endothermic ?:

Questions:

1. What happens to the energy in an exothermic reaction?

2. What happens to the energy in an endothermic reaction?

3. Which of the reactions were exothermic?

4. How do you know it was exothermic? What is your evidence?

5. Which of the reactions was endothermic?

6. How do you know it was endothermic? What is your evidence?

7. Draw a model showing the flow of energy in Part 1 & Part 2 of the laboratory.

8. Which of these examples is exothermic, endothermic and explain why (Remember to think about what is happening to the molecules!).

            a. A lightstick is cracked and begins glowing

            b. Making ice cubes

            c. Cooking an egg