Chapter 3: Matter and Energy

Chapter 3:

Matter and Energy

CHM 130 GCC Chemistry

3.1 Three States of Matter: Gas

Gas: Particles are far apart and are in

constant motion.

Gases have no set shape, they assume shape of the container.

Gases have no set volume, it is variable

 If volume increases, particles move farther apart.

 If volume decreases, particles move closer together.

Liquid: Particles are close together but are free

to flow around one another.

Liquids assume shape of the container.

Volume is constant (can’t compress).

Solid: Particles are packed tightly together &

organized in a rigid pattern; the atoms vibrate in place.

Solids have a definite, fixed shape.

Volume is constant.

Three States of Matter: Liquid, Solid

Ways to Draw the States of Matter

Cool animations

States of Matter - interactive:

http://phet.colorado.edu/en/simulation/states-of-matter-basics

http://phet.colorado.edu/en/simulation/states-of-matter

3.2 Definitions

atoms (He) or diatomic molecules (O2), cannot be

broken down further chemically

 Compound – two or more different atoms bonded

together, can be broken down chemically into elements

 Pure – all particles are the same, cannot be

physically separated

 Mixture – two or more different particles mixed

This is how we draw

atoms of an element

Molecules of an element, if same

2 or more atoms bonded together =

Molecules of a Compound, if different

Examples

•Mixtures

• Metal alloys like 18-K gold, brass • Sand, granite, rocks

• Tap water

• Air which consists of nitrogen, oxygen, and other trace gases.

•Pure

• Salt (NaCl) is a compound • Diamond (C) is an element

• Distilled water is a compound (H₂O) • Mercury is an element (Hg)

element compound mixture

For each image, indicate if it represents 1) pure substance or mixture

3.3 Elements

1. Each element has a unique name, symbol, and atomic number

2. Capitalize the first letter of element name: hydrogen = H, carbon = C

3. If there’s a 2nd_{letter it is lower case:}

helium = He calcium = Ca cobalt = Co

Be careful! CO is carbon monoxide, Co is cobalt

Some symbols are from English names:

hydrogen=H; oxygen=O; Helium=He

Some are from Latin names:

lead Pb (

)

gold Au (aurum means “golden dawn”)

Element Symbols and Names

Know the Names and symbols of the first 20 elements of the Periodic Table and the following:

Ag

Au

Pb

Br

I

Hg

Let’s name them!

Periodic Table: You already know many of these

3.4 Metals, Nonmetals, and Semimetals

(Fig. 3.5)

1. Metals are on the left side of the stair-step line

2. Nonmetals (except H) are located on the right side of the stair-step line

3. Semimetals are touching the stair-step line following B

Properties of Metals vs. Nonmetals

Metals Nonmetals shiny appearance dull appearance malleable, ductile

All solids but Hg

Brittle solids Many gases density – usually high

melting point - high

density – usually low melting point low

Physical States of the Elements at 25 ˚C and normal atmospheric pressure

KNOW THESE:

• Only mercury (Hg) and bromine (Br2) are

liquids

• H2, N2, O2, F2, Cl2, and all Noble gases

(Group VIIIA) are gases • All other elements are solids

Physical states of the elements

7 Diatomic elements

Diatomic means two atoms bonded

together

Have no fear of ice cold beer!

H2(g) N2(g) F2(g) O2(g) I2(s) Cl2(g) Br2 (l)

Two Diatomic Elements

Bromine Br

and Iodine I

(s)

I should be able to point at any element and you tell me:

1. Name (for some of them) 2. Solid, liquid, or gas 3. Diatomic or not

4. Metal, semimetal, nonmetal

Let’s play! I’ll point at several elements, and you identify the four properties above.

Names and Properties of the Elements

3.5 Compounds and Chemical Formulas

• Formulas tell us:

• Type of atoms = element symbols

• Number of atoms = subscripts

• But NOT their bonding order

Ex: water = H₂O  2 H atoms, 1 O atom

but the structure of water is not H-H-O

Ex: How many atoms in potassium nitrate = KNO₃ ___ K, ___ N, ___ O atoms

Chemical

Formulas

Practice Problems

1) How many of each atom are in (NH₄)₃PO₄? What is the total number of atoms?

2) How many atoms of each element are present in Viagra: C₂₂H₃₀N₆O₄S ?

3) How many atoms of each element are in lactic acid: CH₃CHOHCOOH?

Law of Definite Composition

Compounds always contain the same elements in the same proportion by mass.

Ex: Water, H₂O, always contains 11.2 % H and 88.8 % O by mass whether you have a glass full, a swimming pool, or an ocean.

Ex: Table salt, NaCl, is always 39.34% Na and 60.66% Cl ions by mass.

Physical: color, odor, taste, texture, melting point, physical state (s, l, or g), density, solubility, conductivity, hardness

Chemical: describe how a substance reacts or behaves. (explosive, corrosive, toxic, inert, reactive, rusts, oxidizes, decomposes, etc.); We can only identify these when substances react with other substances!!

3.6 Physical and Chemical Properties

Physical change: a change that keeps chemical composition the same, the molecules stay the same with the SAME formula.

Physical Changes ARE changes in state: (s  l  g)

3.7 Physical and Chemical Changes

Note that the H₂O molecules remain H₂O regardless of whether the sample is a solid, liquid, or gas; changes in physical state are

Physical Changes – learn these 6 terms Review Physical Changes – know these terms!

Physical Changes

• Atoms are always moving, even in solid state. Motion doesn’t stop until we reach 0 Kelvin (theoretically). • When you heat ice, the water particles gain kinetic energy

and move faster.

• When particles gain enough energy to overcome attractive forces the solid will melt  liquid.

• If we keep heating the liquid, the particles gain more KE & move even faster  gaseous state

Chemical Changes: a process that changes the chemical

composition, the molecules break apart and rearrange. The formula CHANGES. (aka chemical reactions)

Starting substance is destroyed and a new substance with different properties is formed.

Ex: burning gas

Indicators of chemical reaction:

These may indicate chemical change





(thus not boiling)

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Chemical Reactions

REACTANTS  PRODUCTS

Starting substances are called reactants; New substances formed are called products.

Ex: Chemical reaction between sodium metal Na(s)

and chlorine gas Cl₂(g). They produce salt (NaCl) which is a

totally different chemical with different formula and

properties than the reactants.

Matter or mass cannot be created or destroyed. What

we start with is the same mass as what we end up with.

mass of the reactant(s) = mass of the product(s)

Two reactants make 4.0 grams of product. If one reactant was 1.5 grams, the other was ________.

A + B  C 1.5 g + ___ = 4.0 g

3.8 Law of Conservation of Mass

3.9 Kinetic Energy - Energy of motion

• Water flowing over a dam • Working out

• Dancing

• Burning gasoline • Atoms moving

Potential Energy - Stored Energy

• Water behind a dam

• Gasoline or coal

• Chemical bonds in food

• Car at top of roller coaster

KE, Temp, and physical state



move and vibrate faster, the temperature ____________. As kinetic energy increases a solid will eventually turn into a ____________. And as the KE increases even more it will eventually turn into a ____________.



Energy cannot be created or destroyed, only

converted from one form to another.

Ex: When we digest food its stored energy

(potential) is converted to kinetic energy to do

work.

• Radiant (light, UV, radiowaves, etc.) • Heat

• Chemical (stored in bonds) • Electrical

• Mechanical • Nuclear

6 Other Forms of Energy

_{Chapter 3 Self Test}

Page 97

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Try # 1 – 2, 4 – 9, 13, 14

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Answers in Appendix J