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Chapter 3: Introduction ToChemistry

I. Matter and Atoms

A. Matter1. Different types and arrangements of matter

make up different things.2. Matter is anything which has mass and

volume.a. Mass – the quantity of matter in an object.b. Volume – the amount of space an object takes

upc. Two objects can have the same volume but have

different mass densityd. Weight – the force of gravity on an object. The

more mass an object has the greater the weight.

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B. Physical Properties1. Physical properties - Physical properties

can be observed and measured. Color Mass Volume Shape Melting point Boiling point

C. Chemical Properties

1. Chemical properties - Behavior of asubstance during a chemical reaction. Toxicity Flammability Reactivity Acidic or basic

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Physical Change vs. ChemicalChange Physical Change - A change which does not

change the substance’s chemical identity. (Itis still the same substance) Painting a piece of wood Freezing water Tearing a piece of paper

Chemical change - The change of onesubstance into another substance. Burning a piece of wood Cooking food Rusting metal

D. Examples of Physical andChemical Changes.1. Here are some changes in matter. Which

changes are physical? Which changes arechemical? Frying an egg. Boiling water. Painting a car. Digesting food. Crumpling a piece of paper Decaying leaves.

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E. What is matter made up of?1. Matter is made up

of individual atoms.2. An atom is the basic

unit of matter.

F. What is an atom made upof?1. Atoms are made up of even smaller particles

called subatomic particles.2. The center of the atom is called the nucleus.

a. Made up of protons and neutrons.b. The nucleus makes up 99.9% of the mass of an

atom.c. The proton is positively charged.d. The neutron has a neutral charge.

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Electrons.1. Electrons circle

the nucleus.2. An electron has a

negative charge.3. The number of

electrons equals thenumber of protonsgiving the atom aneutral charge.

G. What is an atom made upof?1. Atomic Number – The number of protons

a. The atomic number identifies an atom.b. Changing the atomic number changes the atom.

2. Mass Number or Atomic Mass – Thenumber of protons plus the number ofneutrons.

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H. The Periodic Table.1. The periodic table is

arranged by atomicnumber.

2. The periodic table alsogives us the atomicmass for each atom.

3. Each symbol on theperiodic tablerepresents a type ofatom.

J. Atomic Symbols

Cl35

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Atomic mass

Atomic number

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Example Problems A neutral atom has 8 protons. How many

electrons does it have? How many protons, neutrons and electrons

does an atom of K have? An atom has an atomic number of 11 and a

mass number of 23. How many neutronsdoes it have?

A neutral atom has 10 protons. Whatelement is it?

An atom has an atomic number of 80. Whatelement is it?

A Few More Examples

27Al, 40Ar, 84Kr13 3618

What is the atomic number?

What is the atomic mass?

How many protons, neutrons andelectrons?