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Chemical reactions are often associated with experiments that happen in test tubes, but almost everything around you is the result of a chemical reaction.

Simply put, a chemical reaction is any process that changes one substance (chemical "thing") into another. This occurs when bonds form or are broken between different atoms. Bonds allow atoms of specific elements to join together to become many different substances. Therefore, everything around and inside you that isn't a singular element is the product, or end result, of a chemical reaction. The substances that react to form these products are called reactants.

Chemical reactions are typically depicted in the format $A + B \rightarrow C + D$, where the items before the arrow are the reactants, and the items the arrow is pointing to are the products. A reaction that can go back and forth is written as $A + B \rightleftharpoons C + D$. In this case, A and B are the reactants of the "forward reaction" and the products of the "backwards reaction." We'll learn more when we study equilibrium

As you'll learn soon, bonds are formed to lower the energy of the participating atoms. Therefore, making bonds releases energy, and breaking bonds takes energy. Because of this, reactions usually either release or use energy. Reactions that release energy in the form of heat are called exothermic, while reactions that need energy, or lower the temperature of their surroundings, are called endothermic.

###Chemical Reactions

When a chemical reaction happen, something new is created from the starting materials.

Everyday examples can occur in our kitchens! When a cake is baked, a chemical reaction occurs. The combination of different ingredients, along with the heat from the oven, cause chemical reactions. Through these chemical reactions a cake is formed!

How do you tell if the reaction is a chemical change? Try removing the eggs or the oil from the cake. Can it be done? No! This is because the ingredients were changed on a chemical level to create something new. We cannot remove the individual ingredients from the newly formed cake. The properties of of the new substance are completely different from the starting ingredients.

As you learn more about chemistry and chemical compounds, you'll see chemical reactions are written as equations. These equations are a simplified way to write and describe chemical reactions.

$$A+B\rightarrow C+D$$ $$\textit{The generic chemical reaction}$$

A chemical reaction changes the configuration of atoms. We express chemical reactions using equations like the one above. There are 3 parts to a chemical equation: reactants, products, and an arrow. Reactants are the chemicals that enter a reaction. Products are the chemicals that leave a reaction. The arrow always points from the reactants to the products. Typically reactants are on the left and products are on the right, but this is not true 100% of the time. Always look at the arrow to determine products and reactants.

Chemical equations must always be balanced. A balanced equation implies 2 things. The amount and type of each atom are the same on both sides, and the total charge of each side must be the same. The idea of a balanced equation directly supports that only the configuration of atoms change in a reaction.

In this problem, the arrow points in the opposite direction from what is typically seen. This means the reactants are on the right. Thus, the reactants are $D$ and $E$.

$$\color{red}{\text{Review}}$$

$\color{red}{\text{Reactants}}$: The chemicals that enter a reaction $\\$ $\color{red}{\text{Products}}$: The chemicals that leave a reaction $\\$ $\color{red}{\text{Balanced}}$: Each side of a reaction must have the same number and variety of atoms, and the same total charge

(Video) Types of Chemical Reactions

by Melissa Maribel

This quick video will teach you all you need to know about types of chemical reactions. Melissa goes over the following six things:

• Synthesis (combination)
• Decomposition
• Single replacement (single displacement)
• Double replacement (double displacement)
• Combustion
• Acid-base neutralization

A chemical reaction is a process in which chemicals interact to form new substances. You see chemical reactions everyday! Have you ever seen something made of metal develop rust over time? Have you ever baked a cake? Ever lit a match? That's right; all these involve chemical reactions!

When chemicals interact, the atoms interacting with each other are called reactants, and the new substances they form are called the products. You'll need to learn more about this as you work with chemical equations. There are many different types of chemical reactions, and specific branches of chemistry often focus on just one type or sub-type of reaction.

Now, in order for a chemical reaction to occur, there must be a chemical change. When an ice cube melts, it's still water, just in a different form. We changed it from a solid to a liquid. So, this is a physical change, not a chemical change, since you do not end up with a new substance. In this case, it is called a phase change.