How to Tell If a Reaction Is Endothermic or Exothermic

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If you want to know whether a reaction is endothermic or exothermic, you need to understand what these two words mean. An endothermic reaction is a reaction caused by absorbing heat, whereas an exothermic reaction is caused by releasing heat. They are very different in this way. Heat is thermal energy, and this is the catalyst for the reaction. You can think of many everyday events that would qualify as one of these reactions. Read on to learn how to tell if a reaction is endothermic or exothermic.

Is the Reaction Caused by Absorbing Thermal Energy?

If you find that a reaction is caused by an object absorbing heat, then it is an endothermic reaction. When the object absorbs the heat from around it, it takes on the heat and the area around it is cooled. For example, when a plant undergoes photosynthesis, it absorbs heat. The plant takes in carbon dioxide, water, and heat from the rays of the sun to create glucose and oxygen. The reaction of the thermal energy from the heat of the sun with the carbon dioxide and water causes the molecules to split apart and form glucose and oxygen. This is an endothermic reaction.

Another example is when you cook an item on the stove. When you turn the stove on, heat is transferred to the pan. The heat causes a food, such as an egg, to change shape. This is an endothermic reaction that causes the food to be cooked.

Is the Reaction Caused by the Release of Thermal Energy?

If the reaction that you observe is caused by the release of thermal energy or heat, then it is an exothermic reaction. In this case, the object releases heat from within. For example, combustion is an exothermic reaction. When you start your car, the vapors from the gas allow the ignition to start the car. This process is a combustion reaction, and it gives off heat. Another example is when water vapor in the atmosphere turns into rain drops, and it releases heat in the process.

Look it up

If you observe a reaction, but you aren’t sure whether it is endothermic or exothermic, you can look it up. You should do a simple Google search of what you observe. For example, if you want to know whether a fire in your fireplace is endothermic, but you aren’t sure whether it is absorbing or releasing heat, you can check online. Heat flows from warm objects to cold objects, so a fire would be exothermic. The fire is releasing the heat. You can come up with other examples, and if you type them in a Google search, you will be able to find the answer.

You can come up with a number of examples because when objects change their form, it is usually from gaining or losing heat. When an ice cube melts, it takes in heat from the surrounding area. This makes ice melting an endothermic reaction. If the external temperature is below zero degrees Celsius, which is the freezing point for water, the ice will not melt. However, if it is warmer, the ice will melt.

All chemical reactions require a transfer of energy, and thermal energy is known for changing the state of many different objects. When you have anything that melts, you will need to know its melting point. Once it reaches that point, an endothermic reaction will occur. On the other hand, you may want to know what can make something warm. When you light a fire to warm up the surrounding area, you are creating an exothermic reaction. The heat from the fire is released and warms the surrounding air.

Understanding the basics of what constitutes endothermic and exothermic reactions makes it fairly easy to determine what kind of reaction you have.

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