Energy is conserved in chemical reactions, so the total amount of energy in the universe at the end of a reaction is the same as it was before the reaction. When a chemical reaction happens, energy is transferred to or from the surroundings. When energy is transferred to the surroundings, this is called an exothermic reaction, and the temperature of the surroundings increases.
Examples of exothermic reactions include:. Everyday uses of exothermic reactions include self-heating cans and hand warmers. When energy is taken in from the surroundings, this is called an endothermic reaction and the temperature of the surroundings decreases.
Examples of endothermic reactions include:.
The Cold Pack: A Chilly Example of an Endothermic Reaction
Everyday uses of endothermic reactions include instant ice packs which can be used to treat sports injuries. The slideshow describes an exothermic reaction between dilute sodium hydroxide and hydrochloric acid and an endothermic reaction between sodium carbonate and ethanoic acid. Sodium hydroxide solution is poured into a beaker of hydrochloric acid which contains a thermometer showing room temperature.
The beaker now contains sodium chloride and water, and the thermometer is showing a rise in temperature, so the neutralisation reaction is exothermic. Sodium carbonate powder is tipped into a beaker of ethanoic acid which contains a thermometer showing room temperature.
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The beaker now contains sodium ethanoate, water and carbon dioxide, and the thermometer is showing a fall in temperature, so this was an endothermic reaction.
In en dothermic reactions, energy en ters. In ex othermic reactions, energy ex its. A study of the energy changes involved in chemical reactions, whether exothermic or endothermic. Reactions and temperature changes Energy is conserved in chemical reactions, so the total amount of energy in the universe at the end of a reaction is the same as it was before the reaction.
Examples of exothermic reactions include: combustion reactions many oxidation reactions most neutralisation reactions Everyday uses of exothermic reactions include self-heating cans and hand warmers. Examples of endothermic reactions include: thermal decomposition reactions the reaction of citric acid and sodium hydrogencarbonate Everyday uses of endothermic reactions include instant ice packs which can be used to treat sports injuries.An instant ice pack is a plastic bag filled with frozen gel that is capable of maintaining extremely low temperatures for an extended period of time.
Unlike traditional ice packs, instant ice packs do not need to be stored in a freezer before use and can freeze instantly through a chemical reaction.5 Amazing Water Experiments & Tricks - Instant Water Freezing (by Mr. Hacker)
Instant ice packs are used therapeutically and are useful in emergency situations since they can be transported at room temperature. Many people also use instant ice packs in coolers to preserve meat, dairy products and other types of food. Instant ice packs use an endothermic reaction between water and ammonium nitrate to achieve cool temperatures rapidly. An endothermic reaction occurs when two separate compounds interact to absorb energy in the form of heat.
Before it is used, an instant ice pack contains both water and ammonium nitrate in separate tubes. When these tubes are broken, the water and ammonium nitrate mix, setting off an endothermic reaction and causing the water to freeze. The freezing of the water prevents all of the ammonium nitrate from instantaneously mixing with the water.
As the ice melts, the water mixes with additional ammonium nitrate, causing additional endothermic reactions and forcing the melted ice to re-freeze. This process allows instant ice packs to remain frozen and maintain extremely low temperatures for an extended period despite being stored or used at room temperature.
Instant ice packs are extremely useful for preserving food, particularly in situations where it is not possible to refrigerate food for long periods. Unlike pure ice, the water from instant ice packs cannot mix with food. Instant ice packs are also significantly more powerful that pure ice: four ice packs, when stored with food in a cooler, provide the same chilling power as 10 to 20 pounds of ice.
Instant ice packs are also used extensively by medical professionals in both emergency and non-emergency situations. Cold temperatures cause muscles to numb and constrict, preventing the muscle from being overworked and allowing it to heal. Instant ice packs are smaller and much easier to transport than pure ice, making ice packs a favorite tool of physical therapists. Instant ice packs are also reusable, which makes them more cost effective than pure ice.
Contributing Writer updated on August 30, Pin Share Tweet Share Email. Overview of Instant Ice Packs. How Instant Ice Packs Work. Uses for Instant Ice Packs. Show Comments.This science project explores endothermic reactions by comparing the temperature change that results from various chemicals added to water.
Did you ever wonder what is inside of a cold pack? You can make a basic cold pack by mixing a salt such as potassium chloride or soda such as baking soda with water. Mixing the two creates a chemical reaction that uses up energy, which makes the mixture colder. You can see which substance cools off water the most by trying out this experiment. Add four teaspoons of sodium bicarbonate to the water and stir with the thermometer. Record the resulting temperature.
Subtract the temperature from Step 2 from the temperature in Step 3. This will give you the change in temperature. Chemical Added. Original Temperature. Final Temperature. Temperature Change. Repeat this process with the citric acid, potassium chloride, sodium carbonate, and calcium chloride.
Record all data. Analyze your data. Which of the substances would create the best cold pack?
The Science Behind a Cold Pack
Bookmark this to easily find it later. Then send your curated collection to your children, or put together your own custom lesson plan. Please note: Use the Contact Us link at the bottom of our website for account-specific questions or issues.A small amount of water is added to zip-loc baggies containing either calcium chloride dihydrate or ammonium chloride.
The resultant solution becomes hot or cold respectively. The bags are passed around the room so that students can directly sense the temperature changes. It is also a great introduction to the concept of entropy, spontaneity, and Gibbs free energy. The number of hot and cold packs used can be varied according to the size of the class. This demo takes a little less than ten minutes.
The exothermic solution of calcium chloride dihydrate is fairly intuitive to most students. The attractions of the calcium ion and the chloride ion for water molecules are greater than their attraction for each other, resulting in solution and the release of energy.
The endothermic solution of ammonium chloride is less intutitive because entropy must be invoked. The ammonium ion and the chloride ion have greater attraction for each other than they have for water molecules, hence the process must absorb energy to proceed.
What drives the process then? The dissolved state is much more disordered and random at the molecular level - the entropy is greater. The entropy increase is great enough to make the process proceed spontaneously, even at a net energy "cost. Concentrated calcium chloride solutions are very irritating to the skin and may cause burns.
Ammonium chloride is a skin irritant. Be sure to close the baggies all the way and instruct students to be careful with them. If someone gets either solution on their skin, wash it off with copious amounts of water.
If someone gets either solution in their eyes, rinse them out with copious amounts of water and seek medical attention. By continuing to view the descriptions of the demonstrations you have agreed to the following disclaimer. The university expressly disclaims all warranties, including the warranties of merchantability, fitness for a particular purpose and non-infringement.
The university further disclaims all responsibility for any loss, injury, claim, liability, or damage of any kind resulting from, arising out or or any way related to a any errors in or omissions from this web site and the content, including but not limited to technical inaccuracies and typographical errors, or b your use of this web site and the information contained in this web siteEducational Resources.
Has this ever happened to you or someone you know? Your teacher grabs the first aid kit and pulls out an instant cold pack. The teacher presses it to your ankle.
It feels cold! An instant cold pack is a plastic package filled with chemicals. When you crunch the cold pack it becomes really cold, really fast. What is happening? How can the chemicals mix and make such a chilly reaction so quickly? The answer can be found in thermodynamics! This is a branch of science that explores the transfer of energy. In thermodynamics, chemical reactions can be classified as endothermic or exothermic.
Exothermic reactions are reactions that give off energy in the form of heat. For example, a fire is one type of exothermic reaction. A fire gives off heat when you burn a fuel source - like wood - in the presence of oxygen. Endothermic reactions are the opposite of exothermic reactions. They take in heat energy from their surroundings. This means that the surroundings of endothermic reactions are colder at the end of the reaction. In chemical reactions like the ones in your cold packthe bonds between molecules in the reactants original chemicals are broken.
New bonds are made in the products what you have left after the reaction happens. Breaking bonds takes energy, and forming bonds releases energy. If more energy is needed to break bonds than is released when the new bonds are formed, you have an endothermic reaction. An instant cold pack is the perfect example of an endothermic reaction.
There are many possible ingredients in an instant cold pack, but they often contain ammonium nitrate and water. The ammonium nitrate is stored in a sealed plastic bag that is surrounded by water. When you pop the plastic that contains the ammonium nitrate solid, it comes into contact with water and dissolves. The chemical reaction between ammonium nitrate and water is an endothermic reaction. The reaction needs more energy than it produces, so it pulls in heat energy from its surroundings and the bag gets cold.
The chemical reaction describing what happens when ammonium nitrate is dissolved in water can be represented as:.Every chemical reaction involves a change in energy.
During the reaction, bonds inside the substances that are reacting together must be broken and new chemical bonds must be formed in the products that are being made.
There are two different types of energy change that can take place. Exothermic reactions involve energy being released. This energy is most commonly a release of heat energy which would be indicated by a temperature rise. Energy could also be released in a chemical reaction in the form of a sound or light being produced but the most exciting chemical reactions will probably have all three going on!
Exothermic reactions happen around us in everyday life. Fuels burning in combustion reactions involve energy being released. Not every exothermic reaction is as exciting as a combustion reaction. When acids and alkalis react together, the energy released is not as obvious.
Mixing the two solutions and stirring results in a small increase in the temperature of the reaction mixture. An endothermic reaction is one in which heat energy is taken in. Normally this is shown by a drop in temperature. There are fewer examples of endothermic reactions in everyday life. Chemical cold packs that are used to treat bumps and sprains use an endothermic reaction to cool down.
Squeezing the cold pack bursts a small inner bag allowing two chemicals to mix. The result is an endothermic reaction that cools the pack down and it can be used to stop or reduce swelling. Energy changes in chemical reactions Every chemical reaction involves a change in energy. Exothermic reactions Exothermic reactions involve energy being released.
Burning fuels like coal is an exothermic process. National 4 Subjects National 4 Subjects up.Please join StudyMode to read the full document. A chemical reaction may involve the motion of electrons in the forming and breaking of chemical bonds. Therefore when a chemical reaction takes place, energy is transferred to, or from, the environment.
A Chemical reaction can either be exothermic or endothermic. Exothermic Reactions During an Exothermic Reaction a transfer of energy to the surrounding, usually in the form of heat, takes place.
This causes an increase in the temperature of the surrounding environment. The process can be easily explained using the change of phases of Water H2O : Liquid water had to have energy put into it to become steam, and that energy is not lost. Instead, it is retained by the gaseous water molecules.
When these molecules condense to form liquid water again, the energy put into the system must be released. And this stored energy is let out as exothermic heat. The same explanation can be used for the process of freezing: energy is put into a liquid during melting, so freezing the liquid into a solid again returns that energy to the surroundings.
The most stable state is where all energy has been released. When going to a more stable state, energy will be released. Due to this temperature drop, cold packs have many benefits when it comes to injuries such as sprains and strains. It cools the local tissue and reduces bleeding, swelling and pain.
It also aids in a speedy recovery. The most commonly used chemical in instant cold packs is ammonium nitrate which will be tested in the investigation along with four other chemicals in water.
These other chemicals include potassium nitrate, potassium chloride, sodium acetate and sodium chloride. The two lowest chemicals will then be mixed together at different concentration ratios to see if this drops the temperature further. Introduction: A chemical reaction is the process of altering the composition and structure of one set of chemical substances to another.
These changes occur due to the movement of electrons breaking and forming new chemical bonds. The students are then going to record the data on a table and later will be able to make a graph of the results.
A hypothesis for this lab could be if ammonium nitrate is added to water then the water temperature will decrease. Hypothesis: If ammonium nitrate is added to water then the water temperature will decrease Materials Goggles Gloves ml beaker ml beaker Chemical scoop Petri dish Petri Dish Accurate Scale 12 grams of Ammonium Nitrate Preciously ml of water Beaker Brush If beaker is not clean TI CBL system and Thermometer Electric Stirrer or Stirring stick Methods Construct a chart that ranges from grams of Ammonium Nitrate and measures the temperature for each gram added Clean out containers if needed Use a scale to measure the out 12 grams of ammonium nitrate Empty the ammonium nitrate in the ml beaker Fill the ml beaker with ml of water Measure the temperature of the water record the data Then add one gram of ammonium nitrate and record the data like before, continue to do this for 10 grams Despose of the ammonium nitrate mixture down the drain while running water Data Grams of Ammonium Nitrate Temp of Water When these chemicals were mixed my first observation was that it turned slurry then it eventually liquefied so I assumed that the product formed was water.
The next thing I observed was when the beaker was lifted up, the wooden block became attached to it because the water froze in between them. This phenomenon showed that the Exothermic and Endothermic Reactions The release of energy in chemical reactions occurs when the reactants have higher chemical energy than the products.
The chemical energy in a substance is a type of potential energy stored within the substance. This stored chemical potential energy is the heat content or enthalpy of the substance. The collection of substances that is involved in a chemical reaction is referred to as a system and anything else around it is called the surroundings. If the enthalpy decreases during a chemical reactiona corresponding amount of energy must be released to the surroundings.
Conversely, if the enthalpy increases during a reactiona corresponding amount of energy must be absorbed from the surroundings.