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Science for Kids11 chapters | 901 lessons
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It's a brisk fall evening and you are huddled around the camp fire with your friends and family for warmth. You hold a stick with a marshmallow on it into the edge of the fire, letting the marshmallow get brown and gooey. Your mom is roasting hot dogs over the fire, while your dad is opening and shaking HotHands hand warmers for each of you to hold. On this perfect evening, chemical changes are happening all around you.
A chemical change is any change that causes a new substance to be formed. For example, when the camp fire has burned completely out, what's left behind? Ashes! Ash is a new substance formed due to the burning of another substance, wood. This is a chemical change. The roasting of the marshmallow is also a chemical change.
The marshmallow gets a brown, crusty substance on the outside of it from roasting over the fire. This new substance on the marshmallow is evidence of a chemical change. Actually, all changes caused by cooking food in any way are chemical changes. How about the hand warmers your dad was opening and shaking? They represent a chemical change as well. When you shake the hand warmers, chemicals mix inside of the packages, creating a new (warm) substance.
There is a common property in all the chemical changes we discussed - not only has a new substance been created, but the change has created heat. There are several chemical properties that help you determine if a chemical change is taking place or not, and one of those is heat, whether the substance is giving off or taking in the heat. Here's a list of other properties that let you know that a chemical change has occurred:
As you may have realized by now, chemical changes happen all around us every day. Let's talk about cooking again. Baking a cake is an example of a chemical change. Think about all of the ingredients that go into a cake (flour, sugar, butter, eggs, baking soda, and so forth). After mixing all the ingredients together and baking the mixture, a new substance is formed: cake. You cannot separate the cake back into its original ingredients, and it gives off heat.
On the Fourth of July, you watch chemical changes in the sky in the form of fireworks, and when you leave your bike outside in the rain, the moisture breaks apart the metal and causes it to rust, which is a property caused by the chemical change. When you eat, the acids in your stomach break apart food and turn it into something different that can't be transformed back into its original substance. Even breathing causes a chemical change. When you take in oxygen, the body processes it and turns it into carbon dioxide.
A chemical change is any change that causes a new substance to be formed, and these changes are happening all around us all the time. They occur when we breathe, cook and set off fireworks, for instance. Looking for chemical properties like heat, light, and explosions is a great way to determine if a chemical change has taken place.
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Science for Kids11 chapters | 901 lessons