ch 3 matter properties and changes

Chapter 3: Matter—Properties and Changes

Section 3.1 Properties of Matter

What is matter?

• Anything that has mass and takes up space

• Mass is a measurement of the amount of matter in an object. It is different than weight which measures the amount of matter AND the gravitational pull on an object.

Now that you’re an expert, which of the following is matter?

1. A book

2. A house

3. A thought

4. Your brain

5. Light

6. Your cell phone

7. Radio waves

Matter Not Matter

There is so many different kinds of matter, that we need to organize it.

Substances have a uniform and unchanging composition

examples: salt,

water,

sugar

Physical Properties of Matter

A characteristic that can be observed or measured without changing the composition of the sample

Properties such as density, color, odor, taste, hardness, melting point, boiling point

1. Extensive: dependent on the amount of substance present

--length, volume

2. Intensive: independent of the amount of substance present

--density, melting point, boiling point

--used to identify substances

Physical Properties of Matter: Two Types

Chemical Properties

Ability or inability of a substance to combine with or change into one or more other substances

• Conducts electricity

• Malleable• Ductile• Reddish brown• Shiny• Density = 8.92

g/cm3

• Melting pt = 1085C• Boiling pt = 2570C

• Forms dark blue solution with ammonia

• Forms green compound when exposed to air

Physical ChemicalProperties

Properties

Classify each as a physical or chemical property:

1. Iron and oxygen form rust.

2. Iron is more dense than aluminum

3. Magnesium burns brightly when ignited.

4. Oil and water do not mix.

5. Mercury melts at -39°C.

Classification based upon the following:

Particle arrangement Energy of particles Distance between particlesState of matter is dependent on

temperature and pressure of the surroundings

States of Matter

3 states of matter

States of Matter

1. Solid—has a definite shape and volume

exs: wood, desk, shoes, sugar

-particles are tightly packed, incompressible

States of Matter

2. Liquids—have a constant volume, -no definite shape-takes the shape of its container-particles are not held rigidly in place,

allows material toflow

3. Gases—have no definite shape or volume-particles are very far apart-particles are easily compressed

States of Matter

Section 3.2

Changes in Matter

Physical Change

• Changes in a substance’s appearance, not in composition

Types of physical changes:

•Bend, grind, crumple

•Split, crush, twist

•Boil, freeze, melt, vaporize

(changes of state or phase)

Chemical Changes

•A change in the composition of a substance

•Also called a chemical change or chemical reaction

•Ex: rust, corrode, tarnish, rot, burn, ferment, explode, oxidize

becomes

becomes

The substance has changed.

Evidence of Chemical Change

2. Energy change: absorbed or released

3. Odor changes or production

4. Gas production

5. Precipitate formation

Classify each as a physical or chemical change:

1. A dead fish rotting

2. Dissolving salt in water

3. Boiling salt water until only salt remains

4. Melting steel

5. Bending steel

6. Cracking ice

Law of Conservation of Mass

Mass is neither created nor destroyed during a chemical reaction—it is conserved. (Antoine Lavoisier)

Mass of reactants = Mass of products

Antoine Lavoisier—a French scientist

o 1743-1794

o Father of Modern Chemistry

o One of the first to use an analytical balance

When you burn a big pile of wood, why do you only end up with a tiny

pile of ashes?

In an experiment, 10.00 g of red mercury (II) oxide powder is placed in an open flask and heated until it is converted to liquid mercury and oxygen gas. The

liquid mercury has a mass of 9.26 g. What is the mass of oxygen formed in the reaction?

Practice problems—pg. 65 #6, 7, 9To collect ---- pg 83 #63,64,65

Section 3.3

Mixtures of Matter

Mixtures

• A combination of 2 or more pure substances in which each pure substance retains its individual chemical properties.

Types of Mixtures

1. Heterogeneous—individual substances remain distinct

2. Homogeneous—has a constant composition throughout

-called a solution

Types of Mixtures

Types of Solutions

• Gas-gas: air

• Gas-liquid: soft drinks

• Liquid-gas: moist air

• Liquid-liquid: vinegar

• Solid-liquid: Crystal Light

• Solid-solid: steel (called “alloys”—mixture of metals producing greater strength)

Separating Mixtures

1. Physical separation: hand selection or pouring through sieves

2. Filtration—uses a porous barrier to separate a solid from a liquid

Separating Mixtures

3. Distillation—based on differences in the boiling points of the substances involved

Separating Mixtures

4. Crystallization—results in the formation of pure solid particles of a substance from a solution containing the dissolved substance

Separating Mixtures

5. Chromatography—separating the components of a mixture based on the tendency of each to travel across the surface of another material.

Separating Mixtures

Section 3.4

Elements and compounds

Elements

• A pure substance that cannot be broken down into simpler substances by physical or chemical means

• 91 naturally occurring elements

• In mid 1800’s, no chart for organizing the elements that were known at the time

Dmitri Mendeleev--1869

-Organized the known elements into a table of rows and columns based on their similarities and masses.

Periodic table

• Organized into horizontal rows called periods and vertical columns called families

• Called “periodic” because properties of elements repeat as you move from period to period

• Mendeleev’s table left blank spaces for elements yet to be discovered and predicted their properties

Compounds • A combination of 2 or more different

elements that are combined chemically

• Most of the matter in the universe are compounds

• Ex: water, sugar, salt, aspirin

Matter

MixturesPure

substances

HeterogeneousMixtures

HomogeneousMixtures Elements Compounds

Dirt, blood, milk

Lemonade, gasoline, steel

Oxygen, gold, iron

Salt, baking soda, sugar

Chemical symbols

• Make it easy to write the formulas for chemical compounds

• Ex: salt water

NaCl

H2O

• Can be broken down into simpler substances by chemical means

• Usually requires energy

Compounds

• Properties of a compound are different from its component elements

• Ex: water—liquid at

room temp.

Compounds

Hydrogen—a colorless, tasteless gas

Oxygen—a colorless, tasteless gas

Sodium chloride

• As a compound, it is a white, unreactive solid that adds flavor to food

• Its component elements:

Chlorine—poisonous, pale, green gas Sodium—a highly

reactive element that fizzes in water

Law of Definite Proportions

• John Dalton

• A pure substance will always have the same percent by weight

• Ex: water (H2O) = 11.2 % hydrogen

88.8% oxygen

To find percent by mass:

Percent by mass = mass of element x 100

mass of compound

Analysis of sugar:

Carbon 8.44 g 42.2%

Hydrogen 1.30 g 6.5%

Oxygen 10.26 g 51.30%

20.0 g sugar

Carbon 211.0 g 42.2%

Hydrogen 32.5 g 6.5%

Oxygen 256.5 g 51.30%

500.0 g sugar

Therefore…

• Sugar always has the same proportions of ingredients

• If a substance has different proportions, it is a different substance

A 78.8 g sample of an unknown compound contains 12.4 g of hydrogen. What is the percent by mass of

hydrogen in the compound?

Percent by mass = mass of element x 100

mass of compound

Practice problems—pg. 76 #21-24To Collect Pg 77 #s25-30

Law of Multiple Proportions

• When different compounds are formed using the same elements, different masses of one element combine with the same relative mass of the other element in small, whole number ratios.

Carbon monoxide/carbon dioxide

O=

C=

O=

C=

1

1

2

1

CO CO2

Copper (I) chloride

Copper (II) chloride