Understanding Chemical Reactions 9/5/23

​Introduction

• ​Chemical Reaction: The process by which one or more substances are changed into one or more different substances

  • ​Two components

    • ​Reactants: the original substances before the reaction takes place

      • Reactants must come together in order for a reaction to take place​

    • ​Products: the resulting substances after the reaction takes place

• ​According to the law of conservation of mass: the total mass of reactants must equal the total mass of the products

Chemical Reactions

Where do chemical reactions occur?

• They happen all the time, every where in the world.

•  Every time you eat, your body uses chemical reactions to break down your food into energy.

• Other examples include metal rusting, wood burning, batteries producing electricity, and photosynthesis in plants.

Signs of a Chemical Reaction

• heat production

• change in temperature

• formation of a precipitate

• change in color

• odor production

• light production

• formation of a gas (bubbles)

What is a chemical reaction?

A chemical reaction is a process where a set of substances undergo a chemical change to form a different substance.

What are reagents, reactants, and products?

• Reactants and reagents are the substances that are used to bring about the chemical reaction

•  A reactant is any substance that is consumed or used up during the reaction.

• The substance that is produced by a chemical reaction is called the product.

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The subscripts show how many atoms are present in the molecule. ​

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The coefficients show the number of molecules present in the chemical reaction.

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Chemical Equation

An expression representing a chemical reaction.

Products (Term)

• The new substance made after a chemical reaction

• Examples include Salt (NaCl) after sodium and chlorine combine

Reactants (Term)

• The substances in a chemical reaction that chemically combine

• Examples would be the combination of sodium and chlorine

Law of Conservation of Mass

​Clear Learning Target:

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I can define the Law of Conservation of Mass so that I can determine if examples given follow the rule.

​Law of Conservation of Mass

​Antoine Lavoisier - "Revolutionized Chemistry"

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• ​Lavoisier discovered that "Mass can not be created or destroyed" by carefully measuring the product and reactants in many of the chemical reactions he was researching.

• ​Law of Conservation of Mass states that: "Mass can not be created or destroyed"

TRUE!

The Law states matter is neither created nor destroyed as seen in this image. We started with 100g and when we broke apart the elements they STILL equal 100g of mass.

Law of Conservation of Mass

During chemical reactions, matter is neither created nor destroyed. It is only transformed from one form to another. Mass ALWAYS remains the same.