The document describes two experiments on exothermic and endothermic chemical reactions. The first experiment combines zinc powder with hydrochloric acid, causing the temperature to increase. The second experiment mixes sodium hydrogen carbonate and citric acid, causing the temperature to decrease. Safety precautions are outlined for handling the chemicals. Procedures are provided for performing each experiment and recording temperature changes to determine whether the reactions are exothermic or endothermic.

1. HEATS OF REACTIONS · MIREIA JIMÉNEZ ROSÉS · DAVID VÁZQUEZ CALDERERO ·

4. EXPERIMENT 1 MATERIALS THERMOMETER SPATULA GRADUATED CYLINDER TEST TUBE TEST TUBE RACK POWER ZINC CLORHIDRIC ACID

5. PROCEDURE 1. PUT ABOUT 5 CM 3 OF CLORHIDRIC ACID. 2. RECORD THE TEMPERATURE OF THE CLORHIDRIC ACID. 3. ADD A SPATULA OF POWDERED ZINC. 4. WATCH WHAT HAPPENS AND TAKE THE TEMPERATURE OF THE SOLUTION.

6. EXPERIMENT 2 MATERIALS SODIUM HYDROGENCARBONATE CITRIC ACID TEST TUBE TEST TUBE RACK THERMOMETER SPATULA GRADUATED CYLINDER

7. PROCEDURE 1. IN A DRY TEST TUBE MIX ONE SPATULA OF CITRIC ACID AND ONE SPATULA OF SODIUM HYDROGENCARBONATE. 2. PUT 2 CM 3 OF WATER IN ANOTHER TEST TUBE. 3. RECORD THE TEMPERATURE OF THE WATER. 4. ADD THE MIXTURE TO THE WATER. 5. WATCH WHAT HAPPENS AND TAKE THE TEMPERATURE OF THE SOLUTION.

8. QUESTIONS INFORMATION NOW DO IT: 1. WHICH REACTION IS EXOTHERMIC AND WHICH ENDOTHERMIC? 2. WRITE WORD AND SYMBOL EQUATIONS FOR EXPERIMENT 1. 3. WRITE WORD EQUATION FOR EXPERIMENT 2. The reaction 1 is EXOTHERMIC, because the temperature increase 23.5ºC. The reaction 2 is ENDOTHERMIC, because the temperature decrease 10ºC. Clorhidric acid + zinc  zinc chloride 2 HCl+ Zn  ZnCl 2 + 2 H Sodium hydrogencarbonate + citric acid  sodium citrate + water + carbon dioxide EXPERIMENT TEMPERATURE OF LIQUID FINAL TEMP. OF MIXTURE TEMPERATURE CHANGE 1 21ºC 44.5ºC +23.5ºC 2 21ºC 12ºC -10ºC

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