Chapter: Matter

Table of ContentsTable of Contents

Section 3: Properties of Matter

Section 1: Atoms

Section 2: Combinations of Atoms

Mission 6 Notes Part IM-6

• Matter is anything that has mass and takes up space.

• Heat and light are not matter, because they have no mass and do not take up space.

The Building Blocks of Matter

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• The forms or properties of one type of matter differ from those of another type because matter is made up of tiny particles called atoms.

Atoms

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• The structures of different types of atoms and how they join together determine all the properties of matter that you can observe.

Atoms

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• Like atoms, the same few blocks can combine in many ways.

• The building blocks of matter are atoms.

• The types of atoms in matter and how they attach to each other give matter its properties.

The Structure of Matter

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• Most other objects that you see also are made of several different types of atoms.

• Some substances are made of only one type of atom.

Elements

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• Elements are substances that are made of only one type of atom and cannot be broken down into simpler substances by normal chemical or physical means.

• Minerals usually are combinations of atoms that occur in nature as solid crystals and are usually found as mixtures in ores.

• Some minerals, however, are made up of only one element.

Elements

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• These minerals, which include copper and silver, are called native elements.

• When something is too large or too small to observe directly, models can be used.

• A model is a small version of a larger object.

Modeling the Atom

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• More than 2,300 years ago, the Greek philosopher Democritus (di MAH kruh tuss) proposed that matter is composed of small particles called atoms.

• More than 2,000 years later, John Dalton expanded on these ideas. He theorized that all atoms of an element contain the same type of atom.

The History of the Atomic Model

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• Three basic particles made up an atom— protons, neutrons (NOO trahnz), and electrons.

• Protons are particles that have a positive electric charge.

Protons and Neutrons

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• Neutrons have no electric charge.

Protons and Neutrons

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• Both particles are located in the nucleus—the center of an atom.

• With no negative charge to balance the positive charge of the protons, thecharge of the nucleus is positive.

• Particles with a negative charge are called electrons, and they exist outside of the nucleus.

Electrons

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• In 1913, Niels Bohr, a Danish scientist, proposed that an atom’s electrons travel in orbitlike paths around the nucleus.

• Over the next several decades, research showed that electrons can be grouped into energy levels, each holding only a specific number of electrons.

The Current Atomic Model

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• Also, electrons do not travel in orbitlike paths. Instead, scientists use a model that resembles a cloud surrounding the nucleus. Click image to view movie.

• The number of protons in an atom depends on the element.

Counting Atomic Particles

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• All atoms of the same element have the same number of protons.

• For example, all iron atoms contain 26 protons, and all atoms with 26 protons are iron atoms.

• The number of protons in an atom is equal to the atomic number of the element.

Counting Atomic Particles

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• This number can be found above the element symbol on the periodic table.

• In a neutral atom, the number of protons is equal to the number of electrons.

How many electrons?

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• This makes the overall charge of the atom zero.

• Therefore, for a neutral atom:

Atomic number = number of protons = number of electrons

• Atoms of an element can lose or gain electrons and still be the same element.

How many electrons?

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• Atoms with fewer electrons than protons have a positive charge, and atoms with more electrons than protons have a negative charge.

• Unlike protons, atoms of the same element can have different numbers of neutrons.

How many neutrons?

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• The number of neutrons in an atom isn’t found on the periodic table. Instead, you need to be given the atom’s mass number.

• The mass number of an atom is equal to the number of protons plus the number of neutrons.

How many neutrons?

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• The number of neutrons is determined by subtracting theatomic number from the mass number.

How many neutrons?

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• For example, if the mass number of an atom is 14 and its atomic number is six; it has eight neutrons.

• Atoms of the same element that have different numbers of neutrons are called isotopes.

How many neutrons?

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Section CheckSection Check

11Question 1

__________ is anything that has mass and takes up space.

A. calorieB. HeatC. LightD. Matter

11Section CheckSection Check

Answer

The answer is D. Heat and light are not matter because they have no mass and do not take up space.

Section CheckSection Check

11Question 2

Particles in an atomic nucleus that have no electric charge are __________.

A. electronsB. neutronsC. protonsD. quarks

11Section CheckSection Check

Answer

The answer is B. Electrons have a negative electric charge and protons have a positive charge.

Section CheckSection Check

11Question 3

The mass number of an atom is equal to __________.

A. the number of electronsB. the number of electrons and protonsC. the number of protonsD. the number of protons and neutrons

11Section CheckSection Check

Answer

The answer is D. The number of protons and neutrons in an atom is the mass number of the element.

Section Summary• Section 1 Summary ATOMS• Matter is anything that has mass and takes up space• The nucleus of an atom contains protons with a positive

charge and neutrons with no charge. Electrons, which have a negative charge, surround the nucleus.

• Isotopes are atoms of the same element that have different numbers of neutrons.

• Diagram of an Oxygen molecule

Interactions of Atoms

• There are about 90 naturally occurring elements on Earth.

• A few elements produce many different things because elements can combine in countless ways.

• Each combination of atoms is unique.

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Compounds• When the atoms of more

than one element combine, they form a compound.

• A compound contains atoms of more than one type of element that are chemically bonded together.

• Water is a compound in which two hydrogen atoms are bonded to each oxygen atom.

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Compounds• Compounds are represented by chemical

formulas that show the ratios and types of atoms in the compound.

• For example, the chemical formula for water is H2O.

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• The properties of compounds often are very different from the properties of the elements that combine to form then.

Chemical Properties

• A property that describes a change that occurs when one substance reacts with another is called a chemical property.

• The chemical properties of a substance depend on what elements are in that substance and how they are arranged.

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Bonding

• The forces that hold the atoms together in compounds are called chemical bonds.

• These bonds form when atoms share or exchange electrons.

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Separating Mixtures and Compounds

• Separating the components of a mixture is a relatively easy task compared to separating those of a compound.

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• The substances in a compound must be separated by chemical means.

• This means that an existing compound can be changed to one or more new substances by chemically breaking down the original compound.

Exploring Matter• Seashells and coral reefs

contain calcium carbonate, which has the formula CaCO3.

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• Properties of CaCO3 differ greatly from those of its elements, calcium, carbon, and oxygen.

Section CheckSection Check

22Question 1

Chemical bonds form when atoms share or exchange __________.

A. electronsB. neutronsC. nucleiD. protons

Section CheckSection Check

22Answer

The answer is A. Only the electrons having the highest energy in the electron cloud can form bonds.

Section CheckSection Check

22Question 2

What is the difference between a compound and a molecule?

Compound refers to any substance in which atoms of more than one type of element are chemically bonded together. A molecule is the individual unit or group of atoms connected by covalent bonds.

Answer

Section CheckSection Check

22Question 3

How do compounds differ from mixtures?

In compounds, atoms of more than one type of element are chemically bonded together. Mixtures are composed of two or more substances that are not chemically combined.

Answer

Section Summary• Section 2 Summary Combination of Atoms• Atoms join to form compounds and molecules. A

compound is a substance made of two or more elements. The chemical and physical properties of a compound differ from those of the elements of which it is composed.

• A mixture is a substance in which the components are not chemically combined.

States of Matter• On Earth, matter occurs in four physical

states. • These four

states are solid, liquid, gas, and plasma.

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Click image to view movie.

Solids• The reason some

matter is solid is that its particles are in fixed positions relative to each other.

• The individual particles vibrate, but they don’t switch positions with each other.

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• Solids have a definite shape and take up a definite volume.

Liquids• Particles in a liquid are attracted to each

other, but are not in fixed positions as they are in the solid.

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• The particles in a liquid can change positions to fit the shape of the container they are held in.

Gases

• The particles that make up gases have enough energy to overcome any attractions between them.

• This allows then to move freely and independently.

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• Unlike liquids and solids, gases spread out and fill the container in which they are placed.

Section CheckSection Check

33Question 1

___________ is a measure of the mass of an object divided by its volume.

A. AreaB. DensityC. ForceD. Viscosity

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33Answer

The answer is B. This measurement is usually given in grams per cubic centimeter.

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33Question 2

Which of the following is the most common state of matter in the universe?

A. gasB. liquidC. plasmaD. solid

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33Answer

The answer is C. Stars like the Sun are composed of plasma.

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33Question 3

Which state of matter spreads out and fills its containers?

A. gasB. liquidC. plasmaD. solid

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33Answer

The answer is A. Liquids will take the shape of containers, but will not necessarily fill them.

Section Summary• Section 3 Summary Properties of Matter• Physical properties can be observed and measured

without causing a chemical change in a substance. • Chemical properties can be observed only when one

substance reacts with another substance.

Section Summary• Atoms in a solid are fixed in place• Atoms in a liquid are close together but still can move• Atoms in a gas move quickly and freely• The only substance found in all 3 phases on Earth is

water• Density = Mass/Volume • If a substance is more dense than water it will FLOAT!• If a substance is less dense than water it will SINK!