Introduction to Matter

Introduction to Matter

Middle School

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Learning Objectives

• Define the key terms: matter, atoms, molecules, and pure substances.

• Create models to show how atoms form simple molecules and larger extended structures.

• Differentiate between physical and chemical properties and use them to identify substances.

• Relate a substance's observable properties to its atomic and molecular structure.

• Explain that mass is never lost or gained during physical and chemical changes.

Key Vocabulary

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Matter

Matter is anything that has mass and takes up space, which means it has volume.

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Atom

An atom is the smallest and most basic unit from which all matter is made.

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Molecule

A molecule consists of two or more atoms that are held together by chemical bonds.

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Pure Substance

A pure substance is made of only one type of atom or one type of molecule.

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Compound

A compound is a substance made of two or more elements chemically combined in a set ratio.

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Extended Structure

An extended structure consists of atoms or molecules arranged in a repeating pattern, like a crystal.

Key Vocabulary

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Crystal

A crystal is a type of solid that is formed by a repeating, orderly arrangement of atoms.

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Physical Property

This is a characteristic of a substance that can be observed without changing its basic identity.

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Chemical Property

Describes the ability of a substance to undergo a specific chemical change and form something new.

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Density

Density is the measure of how much mass is contained in a given or specific volume.

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Physical Change

A physical change is a change that alters the form of a substance but not its identity.

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Chemical Change

A chemical change is a process that results in the formation of one or more new substances.

What is Matter Made Of?

• All matter is made of tiny particles called atoms.

• Atoms join together with chemical bonds to form molecules.

• A compound has two or more different elements chemically combined.

Multiple Choice

What are the fundamental tiny particles that constitute all matter?

• Atoms

• Molecules

• Compounds

• Chemical bonds

Multiple Choice

What is the relationship between atoms and molecules?

• They are joined together by chemical bonds.

• They are physically mixed in a container.

• They are separated into different elements.

• They are melted down into a liquid.

Multiple Choice

Based on the information provided, which of the following must be a compound?

• A particle made of two different elements chemically bonded together.

• Any particle made of two or more atoms bonded together.

• A mixture of two or more different substances.

• A single atom of a specific element.

Pure Substances and Atomic Composition

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Individual Atoms

• A pure substance contains only one single type of particle.

• Some are made of individual atoms that are not bonded together.

• An example of this is the noble gas Helium (He).

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Molecules of One Element

• Other pure substances consist of particles that are called molecules.

• These molecules can contain atoms of the exact same element.

• Oxygen gas is made of molecules with two oxygen atoms (O₂).

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Molecules of Compounds

• Pure substances can also be made of molecules with different atoms.

• These specific types of molecules are also called chemical compounds.

• A very common example of a compound is water (H₂O).

Multiple Choice

What is the defining characteristic of a pure substance?

• It is made of only one single type of particle.

• It is made of atoms from at least two different elements.

• It is made of individual atoms that are not bonded together.

• It is something that can be easily separated into parts.

Multiple Choice

What is the main difference between a pure substance made of molecules of one element and one made of molecules of a compound?

• Molecules of an element have one type of atom, while molecules of a compound have different types of atoms.

• Molecules of an element are always gases, while molecules of compounds are always liquids.

• Molecules of an element are not pure substances, but molecules of compounds are.

• Molecules of an element contain single atoms, while molecules of compounds contain bonded atoms.

Multiple Choice

A sample of carbon dioxide contains only CO₂ molecules. How should carbon dioxide be classified based on its atomic composition?

• A pure substance made of a compound, because it consists of identical molecules with different atoms.

• A pure substance made of molecules of one element, because all the molecules are the same.

• A pure substance made of individual atoms, because it contains both carbon and oxygen.

• A mixture, because it contains atoms of two different elements.

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What Are Extended Structures?

• Some solids are made of extended structures, not separate molecules.

• ​Atoms are bonded together in a repeating pattern, creating large structures.

• A salt crystal (NaCl) is a grid of sodium and chlorine atoms.

• Diamonds and metals are also examples of stable, extended structures.

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Multiple Choice

What is the defining characteristic of solids with extended structures?

• They are made of separate molecules that are loosely connected.

• They are made of atoms that are arranged in a random order.

• They are made of atoms bonded together in a repeating pattern.

• They are made of a single, large molecule.

Multiple Choice

According to the information provided, what do salt crystals and diamonds have in common?

• Both are made of sodium and chlorine atoms.

• Both are formed from atoms arranged in a repeating pattern.

• Both are examples of solids made of separate molecules.

• Both are metals that are very good conductors of electricity.

Multiple Choice

If a solid is built from billions of atoms bonded together in a highly organized, repeating pattern, what can you logically conclude about its physical properties?

• The structure would be very strong and stable.

• The structure would be flexible and easily bent.

• The structure would easily break apart into separate atoms.

• The structure would be a liquid at room temperature.

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Physical vs. Chemical Properties

Physical Properties

• ​These are characteristics you can observe to identify a substance without changing its basic identity.

• ​​Every pure substance has a unique set of physical properties under a given set of conditions.

• ​Examples are color, odor, solubility, density, melting point, and boiling point.

Chemical Properties

• ​These describe a substance's ability to undergo a chemical change, becoming a new substance.

• ​​This change results in a substance with a different chemical composition and is not easily reversible.

• ​Examples include flammability (the ability to burn) and reactivity (how it combines with other substances).

Multiple Choice

What is the key difference between a physical property and a chemical property?

• A physical property describes how a substance changes into a new substance, while a chemical property can be observed without changing the substance's identity.

• A physical property can be observed without changing the substance's identity, while a chemical property describes its ability to change into a new substance.

• A physical property relates to a substance's color and odor, while a chemical property relates to its flammability and density.

• A physical property is always reversible, while a chemical property is always permanent.

Multiple Choice

Which of the following statements describes a chemical property of a substance?

• The substance has a boiling point of 100 degrees Celsius.

• The substance is a blue crystal at room temperature.

• The substance dissolves when stirred into water.

• The substance is flammable and burns when exposed to a flame.

Multiple Choice

A scientist is studying an unknown substance. Which investigation would provide the best evidence of one of its chemical properties?

• Observing that the substance is a solid with a specific color.

• Heating the substance until it melts into a liquid.

• Mixing it with another substance causes it to fizz and produce a gas.

• Measuring the substance's density to see if it floats in water.

Understanding Mixtures

• A mixture contains substances that are not chemically bonded together.

• Heterogeneous mixtures have visible parts, while homogeneous mixtures are evenly mixed.

• A solution is a type of homogeneous mixture, like salt in water.

Multiple Choice

What is the key characteristic of the substances that form a mixture?

• They are chemically bonded together.

• They can only be separated by a chemical reaction.

• They always form a new substance.

• They are not chemically bonded together.

Multiple Choice

What is the main difference between homogeneous and heterogeneous mixtures?

• Homogeneous mixtures involve liquids, while heterogeneous mixtures involve solids.

• Homogeneous mixtures are evenly mixed, while heterogeneous mixtures have visible parts.

• Homogeneous mixtures are chemically bonded, while heterogeneous mixtures are not.

• Homogeneous mixtures can be easily separated, while heterogeneous mixtures cannot.

Multiple Choice

If you stir a spoonful of salt into a glass of warm water until it completely disappears, which is the best classification for the resulting liquid?

• A heterogeneous mixture, because it contains both a solid and a liquid.

• A solution, because it is a homogeneous mixture that is evenly mixed.

• A chemically bonded compound, because a new substance was formed.

• A pure substance, because the salt is no longer visible.

Measuring Matter: Mass, Volume, and Density

• Mass is the amount of matter in an object, measured in grams (g).

• Volume is the amount of space that matter takes up.

• Density determines if an object will sink or float in a liquid.

Multiple Choice

Which statement correctly defines mass and volume?

• Mass is the amount of matter in an object, while volume is the amount of space it takes up.

• Mass is the amount of space an object takes up, while volume is the amount of matter in it.

• Mass is measured in liters, while volume is measured in grams.

• Mass determines if an object will float, while volume determines if it will sink.

Multiple Choice

What is the primary function of density when an object is placed in a liquid?

• It measures the amount of matter in the object.

• It measures the amount of space the object occupies.

• It determines whether the object will sink or float.

• It changes the object's color in the liquid.

Multiple Choice

A small rock and a large sponge have the same mass. If both are placed in water, the rock sinks while the sponge floats. Which statement best explains this outcome?

• The rock has more mass packed into the same amount of space.

• The sponge takes up less space than the rock.

• The rock has less mass than the sponge.

• The sponge is heavier than the rock.

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Physical vs. Chemical Changes

Physical Change

• This alters the form of matter but does not create a new substance.

• The chemical composition of the substance remains the same before and after the change.

• Examples include melting ice, dissolving sugar in water, or crushing a can.

Chemical Change

• This is a process where substances are converted into new, different substances.

• Evidence includes bubbles, a color change, or the production of heat or light.

• Examples are burning wood, iron rusting, or the process of baking a cake.

Multiple Choice

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

• A physical change alters the form of a substance, while a chemical change creates a new substance.

• A physical change involves heat or light, while a chemical change involves dissolving.

• A physical change creates a new substance, while a chemical change only changes its form.

• A physical change is always reversible, while a chemical change is always permanent.

Multiple Choice

Which observation provides the best evidence that a chemical change has occurred?

• A can is crushed.

• Sugar dissolves in water.

• Bubbles are produced.

• Ice melts into water.

Multiple Choice

An iron nail is left outside in the rain and, after a few days, develops a reddish-brown, flaky coating (rust). Which statement best explains this process?

• A chemical change is occurring because a new substance (rust) is forming.

• A physical change is occurring because the nail is just changing color.

• A physical change is occurring because the nail's shape has not changed.

• No change is happening because the nail is only getting wet.

Energy and Changes in Matter

• All physical and chemical changes in matter involve energy.

• Thermal energy naturally flows from a warmer substance to a cooler one.

• Changes in matter can either absorb or release energy.

Multiple Choice

What is always involved when matter undergoes a physical or chemical change?

• Energy

• A change in color

• The formation of a gas

• A decrease in mass

Multiple Choice

Which statement describes the two ways energy can be involved during a change in matter?

• Energy is either absorbed or released.

• Energy is either created or destroyed.

• Energy is either positive or negative.

• Energy is either fast or slow.

Multiple Choice

If you place a cool metal spoon into a bowl of hot soup, what will be the direction of thermal energy flow?

• From the hot soup to the cool spoon

• From the cool spoon to the hot soup

• Away from both the soup and the spoon

• Into both the soup and the spoon

Connecting Scales: Macro vs. Micro

• We observe things at macroscopic (visible) and microscopic (unseen) scales.

• A substance's visible properties are determined by its microscopic structure.

• For example, a diamond's hardness comes from its strong atomic structure.

Multiple Choice

What determines the visible properties of a substance, such as its hardness or texture?

• Its properties at the microscopic level.

• The tools used to view the substance.

• The color or brightness of the substance.

• The location where the substance is found.

Multiple Choice

Based on the example of a diamond, what is the relationship between its hardness and its atomic structure?

• The diamond's hardness is a visible property determined by its unseen atomic structure.

• A diamond's atomic structure is a visible property determined by its hardness.

• Hardness and atomic structure are both microscopic properties.

• Hardness and atomic structure are both macroscopic properties.

Multiple Choice

If scientists discover a new material that is extremely soft and falls apart easily, what can be concluded about its microscopic structure?

• Its atoms are likely arranged in a weak or disorganized structure.

• Its atoms are arranged in a strong structure, similar to a diamond.

• The material does not have a microscopic structure.

• Its softness is a microscopic property.

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Common Misconceptions About Matter

Misconception	Correction
Mass and weight are the same thing.	Mass is the amount of matter, while weight is the force of gravity.
When matter is burned, its mass disappears.	Mass is conserved; it changes into new substances like ash and gas.
When a substance dissolves, it vanishes.	The substance's particles are still present, just spread out in the liquid.
Gases are not matter because they are invisible.	Gases have mass and take up the volume of their container.

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Summary

• All matter has mass, takes up space, and is composed of atoms.

• Substances are classified as elements, compounds, or mixtures.

• A substance's properties are determined by the arrangement of its atoms.

• Changes in matter can be physical or chemical, always involving energy and conserving mass.

Poll

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

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