Reaction

Reaction

Middle School

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Learning Objectives

• Describe how synthetic materials are made from natural resources using chemical processes.

• Explain how chemical reactions rearrange atoms to form new substances with new properties.

• Use the Law of Conservation of Mass to explain that atoms are conserved.

• Identify evidence of a reaction and distinguish between exothermic and endothermic reactions.

Key Vocabulary

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Synthetic Material

A man-made substance created from natural resources by way of one or more chemical reactions.

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Chemical Reaction

A process that rearranges the atomic structure of substances to form entirely new substances.

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Reactants

The initial starting substances that are used up and consumed during a chemical reaction.

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Products

The new substances that are formed as the final result of a chemical reaction.

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Conservation of Mass

The principle that matter is not created or destroyed in any chemical or physical change.

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Combustion

A chemical reaction with oxygen that releases stored energy in the form of light and heat.

Key Vocabulary

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Exothermic Reaction

A chemical reaction that releases energy to its surroundings, often in the form of heat.

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Endothermic Reaction

A chemical reaction that absorbs energy from its surroundings, often making the environment feel cooler.

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Flammability

This describes the ability of a certain substance to burn or to ignite, causing a fire.

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Solubility

This is the ability of a given substance to successfully dissolve when it is in another substance.

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Precipitate

An insoluble solid that forms from a solution during a chemical reaction when two liquids are mixed.

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Synthetic Materials and Natural Resources

• Synthetic materials like plastic, nylon, and polyester are created by humans.

• They are made by rearranging atoms from natural resources using chemical processes.

• Petroleum, or crude oil, is a nonrenewable resource used to make synthetics.

• It is also refined for plastics, medicines, fabrics, and household products.

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Multiple Choice

How are synthetic materials such as plastic and nylon created?

• By rearranging atoms from natural resources through chemical processes.

• By mining them directly from the earth in their final form.

• By growing them on specialized farms like crops.

• By mixing different types of recycled materials together.

Multiple Choice

What is the relationship between petroleum and the production of synthetic materials?

• It is a nonrenewable resource that is transformed to create many synthetic products.

• It is a synthetic material that is used to create natural resources.

• It is a renewable resource that can be easily replaced after use.

• It is only used to make fuel and is unrelated to household products.

Multiple Choice

If the world's supply of petroleum decreased significantly, what would be the most likely impact on the production of plastics, medicines, and fabrics?

• The production of these materials would become more difficult because they depend on a limited resource.

• The supply of these materials would be unaffected because they are human-made.

• Humans would easily find a way to create more petroleum.

• These materials would become natural resources themselves.

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What is a Chemical Reaction?

• A chemical reaction is a process that changes reactants into new products.

• During a reaction, bonds between atoms break and new bonds are formed.

• The Law of Conservation of Mass states that atoms are not created or destroyed.

• The total number and type of atoms remain the same during a reaction.

Multiple Choice

What is the main outcome of a chemical reaction?

• It turns starting substances into new substances.

• It causes substances to change their state, like melting.

• It mixes different substances together without changing them.

• It makes the starting substances disappear completely.

Multiple Choice

How are new substances formed during a chemical reaction?

• By creating entirely new atoms to make the products.

• By breaking bonds in reactants and forming new bonds in products.

• By destroying the atoms of the reactants completely.

• By simply mixing the atoms of reactants like a salad.

Multiple Choice

If a sealed container with reactants has a mass of 50 grams, what is the most likely mass of the products after the reaction is complete, and why?

• 50 grams, because the atoms were rearranged to form new products, but no atoms were lost.

• Less than 50 grams, because some of the reactant atoms were destroyed during the reaction.

• More than 50 grams, because the products captured new atoms from the air, increasing the mass.

• 50 grams, but the reaction failed to produce any new substances.

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Evidence of a Chemical Reaction

• In a chemical reaction, new substances with different properties are formed.

• A change in temperature or color can show a reaction has occurred.

• Gas production or the formation of a solid (precipitate) are also clues.

• A new smell or a change in a substance's flammability is also evidence.

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Multiple Choice

What is the main result of a chemical reaction?

• A new substance with different properties is formed.

• A substance changes its state, like melting.

• A substance is mixed with another substance.

• A substance gets smaller or breaks apart.

Multiple Choice

Which of the following is a key piece of evidence used to identify a chemical reaction?

• The formation of a solid precipitate from two liquids.

• A solid substance dissolving in a liquid.

• A liquid freezing to become a solid.

• An object changing its shape or size.

Multiple Choice

A camper burns a log. The wood changes to black ash, releases gas, and produces light and heat. Why are these changes considered evidence of a chemical reaction?

• Because new substances like ash and gas were formed, and the properties of the wood changed.

• Because the log changed its color and shape.

• Because the log produced heat, which is a physical change.

• Because the log is no longer a solid piece of wood.

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Energy in Chemical Reactions

Exothermic Reaction

• A chemical reaction that releases energy, usually in the form of heat.

• The process of combustion, like burning wood, is a classic exothermic reaction.

• This reaction causes the temperature of the surrounding area to increase significantly.

Endothermic Reaction

• A chemical reaction that absorbs energy from its surroundings, often as heat.

• Instant cold packs use an endothermic reaction to become cold very quickly.

• This reaction causes the temperature of the surrounding area to decrease noticeably.

Multiple Choice

What is the primary difference between how exothermic and endothermic reactions involve energy?

• Exothermic reactions release energy, while endothermic reactions absorb energy.

• Exothermic reactions create energy, while endothermic reactions destroy energy.

• Exothermic reactions only produce heat, while endothermic reactions only produce cold.

• Exothermic reactions are fast, while endothermic reactions are slow.

Multiple Choice

What is the relationship between the type of chemical reaction and the temperature of its surroundings?

• Exothermic reactions cause the temperature to increase, while endothermic reactions cause it to decrease.

• Both types of reactions cause the temperature of their surroundings to increase.

• Both types of reactions cause the temperature of their surroundings to decrease.

• The temperature change depends on the chemicals used, not the type of reaction.

Multiple Choice

If burning wood is an exothermic process and an instant cold pack is an endothermic process, what conclusion can be drawn about energy in these two reactions?

• The burning wood releases heat, while the cold pack absorbs heat from its surroundings.

• The burning wood gets hotter because it is on fire, while the cold pack gets colder because it has ice.

• Both reactions are examples of combustion, but one is hot and one is cold.

• The wood creates new energy as it burns, while the cold pack destroys energy to become cold.

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The Chemistry of Fireworks

• Fireworks are exothermic combustion reactions that transfer energy as heat and light.

• They require five ingredients: a fuel, an oxidizer, color chemicals, chlorine, and a binder.

• The colors are made by burning different metal elements like strontium for red.

• An oxidizer provides oxygen to break the fuel's bonds, causing the explosion.

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Multiple Choice

What type of reaction is responsible for the heat and light released by fireworks?

• An exothermic combustion reaction

• A chemical reaction that absorbs energy

• A reaction that creates new elements

• A physical change from solid to gas

Multiple Choice

What is the relationship between the fuel and the oxidizer in a firework?

• It provides the oxygen needed to break the fuel's bonds for an explosion.

• It burns different metal elements to create specific colors.

• It transfers energy as heat and light to the surroundings.

• It holds all the other chemical ingredients together in the firework.

Multiple Choice

If a firework were made with all its ingredients except for the metal elements like strontium, what would be the most likely result?

• The firework would explode but would not produce a specific color.

• The firework would fail to explode.

• The firework would produce a white light instead of a color.

• The firework would be much louder than usual.

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The Father of Modern Chemistry

• Antoine-Laurent Lavoisier is known as the ‘father of modern chemistry’.

• He conducted quantitative experiments, using careful measurements to understand chemical reactions.

• He famously disproved the phlogiston theory by showing substances gain weight when burned.

• He named oxygen and established the Law of Conservation of Mass.

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Multiple Choice

What is Antoine-Laurent Lavoisier primarily known as?

• The father of modern chemistry

• The inventor of the microscope

• The discoverer of electricity

• The creator of the periodic table

Multiple Choice

Which statement best describes the methods and discoveries of Antoine-Laurent Lavoisier?

• He used careful measurements to understand reactions and established the Law of Conservation of Mass.

• He focused only on observing the colors of substances during reactions.

• He proved the existence of atoms by splitting them apart.

• He helped to develop the phlogiston theory to explain burning.

Multiple Choice

Lavoisier showed that substances gain weight when they are burned. What is the most logical conclusion from this observation?

• The substance combined with something from the air.

• The phlogiston theory must have been correct.

• The experiment's measurements must have been wrong.

• The substance lost all of its mass during the reaction.

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Carbon and Organic Compounds

• Organic compounds are essential for all life and always contain the element carbon.

• Carbon atoms can bond together to form long chains and complex rings.

• This property allows for millions of molecules, creating life’s vast diversity.

• The search for life on other planets is often a search for carbon.

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Multiple Choice

Which element is always found in organic compounds and is considered essential for all life?

• Carbon

• Oxygen

• Water

• Nitrogen

Multiple Choice

What is the relationship between carbon's atomic structure and the diversity of life?

• It is the most common element found on Earth.

• It dissolves easily in water, helping transport nutrients.

• It can form long chains and complex rings, allowing for a vast number of different molecules.

• It is a gas at room temperature, making it easy to inhale.

Multiple Choice

Why would scientists looking for life on other planets prioritize the search for carbon?

• Because carbon is the only element that can be detected from Earth.

• Because carbon is the main source of heat and energy on other planets.

• Because carbon is the heaviest element and is easiest to find.

• Because carbon's unique ability to form complex structures is considered necessary for life to exist.

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Common Misconceptions About Chemical Reactions

Misconception	Correction
Burning something destroys the matter completely.	Matter is conserved, not destroyed. Atoms are rearranged into new substances.
All chemical reactions release heat.	Some reactions, called endothermic reactions, must absorb heat to occur.
Chemical reactions can turn one element into another.	Reactions only rearrange atoms into new compounds. The elements do not change.
An equation is balanced when molecules are the same on both sides.	An equation is balanced when atoms of each element are equal on both sides.

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Summary

• Synthetic materials and organic compounds are products of chemical reactions.

• Chemical reactions rearrange atoms from reactants into new products with new properties.

• Evidence of a reaction includes changes in temperature, color, or forming a gas.

• In reactions, atoms are conserved and can either release or absorb energy.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

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