Chapter 12 Lesssons

Chapter 12: Changes in Matter

You Will Discover:

• Ways that substances can change• How to describe and classify chemical

reactions• How we can use chemistry to separate

substances• How chemical technology improves our

lives

Vocabulary:• Physical change: a change in some properties of matter

without forming a different kind of matter• Chemical change: the changing of a substance or kind of

matter into a different kind of matter with different properties

• Combustion: the process of burning• Reactant: substance used in a chemical reaction• Product: substance made during a chemical reaction• Chemical equation: a formula that describes a chemical

reaction• Polymer: a large molecule made of many smaller units

connected together• Chemical Reaction: when one or more substances change

into other substances with different chemical properties

Lesson 1: What are Chemical Changes?

Physical ChangesChanges in:

• Position

• Shape

• Size

• Volume

• Phase of matter

Chemical Change*occurs when one substance or kind of matter changes into another completely

different kind of matter with different

properties

Examples of Physical Change

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Examples of Chemical Change





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Evidence of Chemical Change

• When a chemical change occurs, atoms rearrange themselves to form different kinds of matter.

Examples:• Antacid tablets - tiny bubbles of carbon dioxide

gas• Burning Log - gives off heat and light

Chemical Changes and Energy Changes

During Chemical Changes:

*bonds between atoms break

*new bonds form

This involves taking in or giving off energy.

Example:

Combustion - gives off heat and light

Questions to Discuss

• What is the difference between a chemical change and a physical change?

• List three types of evidence of chemical change?

• List three types of physical changes?• Look at the pictures of the copper tree on

pages 376 and 377, what evidence of a chemical change do you see?

Lesson 2 - What are some kinds of chemical reactions?

• During a chemical reaction, one or more substances change into other substances with different chemical and physical properties.

• These substances are called reactants. The reactants undergo a chemical change to produce the product.

Chemical Equations

• A chemical equation is a scientific sentence that shows what is happening during a chemical reaction.

• The reactants are listed on the left side of the equation and the product is found on the right.

Examples of Chemical Equations

2Mg + 02 = 2MgO

Reactants Product

*This chemical equation creates Magnesium Oxide.



Law of Conservation of Mass

• Matter cannot be created or destroyed during a chemical reaction.

• The total mass of the reactants is equal to the total mass of the product.

• Example: If you bake a cake, the mass of the ingredients equals the mass of the cake, plus the gases that come from the oven to make the cake smell good.

Types of Chemical Reactions

• Decomposition reaction - compounds split apart to form smaller compounds or elements

• Combination reaction - elements or compounds come together to form new compounds.

• Replacement reaction - at least one molecule splits apart and the parts of that molecule switch places.



Example of Decomposition Reaction

• Electrolysis of Water

• The water separates into Oxygen and Hydrogen atoms. This compound separates

into the two different molecules.

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Example of Combination Reaction

• Two separate substances are put together and they create a completely different substance with different properties



Example of Replacement Reaction

• In this reaction, the two compounds switch partners to form two new compounds.




• What do chemical equations show?• List and describe the three kinds of chemical

reactions.• When magnesium reacts with oxygen gas a

reactions occurs. What type of reaction it it? Why?

• Using the chemical equation on page 379. If you start with 100 atoms of magnesium, how many molecules of oxygen are needed to react with all the magnesium?

Lesson 3 - How are chemical properties used?

• Chemical Properties can be used:• Separating mixtures

• Separating metals from ores

• Identifying substances

Separating Mixtures

• Substances may also have different chemical properties that can be used to separate them from one another.

• Example:

• Archaeologists use vinegar to separate fossils from limestone. The vinegar dissolves the limestone, freeing the fossil.

Separating Metals from Ores

• Ores are rocks with metals combined with other substances.

• Example:• Iron ore contains iron oxide. Heating iron ore in a

furnace with with solid carbon allows the iron to separate from the oxygen in the ore. The result is pure iron and carbon dioxide.



Iron ore

Identifying Substances

• Scientists use chemical properties to identify substances.

• Acids and bases are two common types of substances.

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Acid Base

Acids and Bases• Acids and Bases react with chemicals in special

paper called universal indicator paper.• Acids turn the paper red

• Bases turn the paper purple

• Universal indicator paper is not enough to completely identify a substance, but helps narrow substances down.



Flame Test

• Scientists use flame tests to identify a substance.

• A material is heated in a flame, different substances will cause the flame to have different colors.




• How can chemical properties be used to separate substances in a mixture or compound?

• What type of reaction is it when purifying iron ore? (2FeO + C = 2Fe + CO2)

• How might a scientist distinguish the following compounds strontium chloride and potassium chloride?

• What color do you think indicator paper would turn if it were dipped in shampoo? Why?

Lesson 4 - How is chemical technology used in our lives?

• Chemistry and Health• Chemistry and New Materials• Chemistry and Transportation• Chemistry and Technology• Chemicals and Safety

Chemistry and Health• Alexander Fleming made an accidental discovery

that led to the development of antibiotics.• Fleming grew bacteria in dishes. One of his dishes

became contaminated with mold. The mold killed the bacteria. Fleming named this mold penicillin.

• Chemists have also identified substances that help people stay healthy. These substances are called vitamins.

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Chemistry and New Materials• Some materials are found in nature, like

wool or cotton.

• Scientists have invented some common materials, like nylon, plastic, and concrete.

• Nylon is a polymer, made of six carbon atom, seven hydrogen atoms, and one nitrogen atom.

• A polymer may have thousands or millions of units in a single chain.


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Plastic Nylon Concrete

Chemistry and Transportation• Natural rubber comes from trees. It bends easily

and is waterproof.• It becomes brittle and cracks in cold weather.

• Scientists discovered that by heating the rubber and adding sulfur they made rubber durable and usable year-round.

• In the 1900s scientists developed a way to make artificial rubber.

• It is used for tires, tennis shoes






Chemistry and Technology



Chemicals and Safety• Some chemicals are used to helps us clean

and sanitize to keep use healthy.

• When using chemicals it is important to:• Read the warning labels• Read the directions for use• Wear gloves and safety goggles• Open a window if necessary• Don’t mix any cleaners



Questions to Discuss• What are the antibiotics and how have they

improved health?• What are three common materials that were

developed by scientists?• How did scientists working with rubber help our

modern system?• Why is it important to avoid mixing cleaners?• What is a polymer?• Which of the technological advances has most

improved human lives?

Education

Chapter 12 Lesssons