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The Chemistry of Ice Cream: An Endothermic Reaction NO LIQUID NITROGEN INVOLVED.

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Presentation on theme: "The Chemistry of Ice Cream: An Endothermic Reaction NO LIQUID NITROGEN INVOLVED."— Presentation transcript:

1 The Chemistry of Ice Cream: An Endothermic Reaction NO LIQUID NITROGEN INVOLVED

2 Intro to Ice Cream One does not need a fancy or expensive ice cream maker to make ice cream. When a milk, sugar, and vanilla mixture is placed into a zip lock bag and surrounded with an ice-salt mixture in a larger zip lock bag, ice cream is produced! Is it magic? No sir! Its another example of how cool thermo-chemistry is!!!

3 Materials 2 quart sized zip lock bags 2 gallon sized zip lock bags Ice cubes to fill large bag ¾ full Toppings 2 cups of Rock Salt Spoon Ice Cream Mixture: – 1 cup of almond milk – ¼ cup of sugar – ½ teaspoon vanilla 2 beakers 2 thermometers Optional: – Chocolate Chips – Sprinkles – Other toppings

4 LETS MAKE SOME ICE CREAM!!!! Banana Splits!!!!!!!

5 Procedure 1. Obtain two beakers and fill one with ice and the other a layered ice-salt mixture. Put a thermometer in each and record the lowest temperature it reaches. 2. Obtain a 2 quart zip lock bag and place your ice cream mixture inside, shake gently to mix. 3. Squeeze out any excess air in the bag and seal the bag securely; test by turning upside down over your local sink. If it leaks at all, transfer to a new bag. Fold the top down a few times and then double bag it. Make sure to squeeze out as much air as possible in the second bag as well. 4. Obtain two gallon-sized bags, ice and two cups of salt. 5. Open the gallon sized bag and layer just the bottom with ice and salt then place the small bag inside the gallon-size one. 6. Continue to layer ice and salt in the gallon-size bag. You should use about cups of salt! Squeeze out any excess air in the bag and seal the bag securely. Place another bag around that, but it actually works better if the final bag has a bit of air into it. 7. Place your bag contraption in the sink and gently agitate by shaking it and rotating it over/in the sink. Turn the bag continuously until the ice cream is the desired consistency. Takes about 15 minutes! Dont squeeze hard or the bags will leak. 8. When done, you can ask your teacher to check it out for you, open and remove the smaller inner zip lock bags and carefully, but quickly rinse just the outside of the bag with tap water to remove the salt solution. 9. Remove the small inner bag from the outer one and share your dessert with spoons. If you want to add some syrup or other toppings, feel free but not wait to long or your tasty treat will melt.

6 How does Ice Cream Relate to Chemistry? Thermo-chemistry: Thermo-chemistry is the study of the energy and heat associated with chemical reactions and/or physical transformations. A reaction may release or absorb energy, and a phase change may do the same, such as in melting and boiling. Thermo-chemistry focuses on these energy changes, particularly on the systems energy exchange with its surroundings. Thermo-chemistry is useful in predicting reactant and product quantities throughout the course of a given reaction. In combination with entropy determinations, it is also used to predict whether a reaction is spontaneous or non-spontaneous, favorable or unfavorable. But………

7 …..How does it relate to Ice Cream? Exothermic Reactions are: An exothermic reaction is a chemical reaction that is accompanied by the release of heat. In other words, the energy needed for the reaction to occur is less than the total energy released. As a result of this, the extra energy is released, usually in the form of heat. Endothermic Reactions are: An endothermic reaction is any chemical reaction that absorbs heat from its environment. – Now which one is it???

8 Take a minute to think as we continue to make some Ice Cream!!! Based on what you have learned is it exothermic or endothermic??

9 THE ANSWER IS….. Endothermic WHY??

10 This Is Why Ice has to absorb energy in order to melt, changing the phase of water from a solid to a liquid. When you use ice to cool the ingredients for ice cream, the energy is absorbed from the ingredients and from the outside environment (like your hands, if you are holding the baggie of ice!). When you add salt to the ice, it lowers the freezing point of the ice, so even more energy has to be absorbed from the environment in order for the ice to melt. This makes the ice colder than it was before, which is how your ice cream freezes. Ideally, you would make your ice cream using 'ice cream salt', which is just salt sold as large crystals instead of the small crystals you see in table salt. The larger crystals take more time to dissolve in the water around the ice, which allows for even cooling of the ice cream.

11 An Example of an ENDOTHERMIC Reaction

12 Do you have any questions? We want to thank Mrs. Garrett for giving us the opportunity to show you how much fun making ice cream is. We really, really hoped that you thoroughly enjoyed our presentation. DeWitt Goss Jon Yalof

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