what is matter? - doral academy preparatory school · 2017-07-27 · breaking down mixtures and...

Matter Section 1

What is Matter?

〉How can matter be classified?

〉Every sample of matter is either an element, a

compound, or a mixture.

• matter: anything that has mass and takes up

space

Matter Section 1

Elements

〉Why are carbon and copper classified as elements?

〉Each element is made of one kind of atom.

• element: a substance that cannot be separated or

broken down into simpler substances by chemical means

• atom: the smallest unit of an element that maintains

the properties of that element

Matter Section 1

Elements in the Human Body

Matter Section 1

Elements, continued

• Elements are represented by symbols. • Atoms that make up a molecule act as a unit.

• molecule: a group of atoms that are held together by chemical forces; a molecule is the smallest unit of matter that can exist by itself and retain all of a substance’s chemical properties

Matter Section 1

Compounds

〉How are elements related to compounds?

〉Each molecule of a compound contains two or more elements that are chemically combined. Elements combine chemically to form a compound.

• compound: a substance made up of atoms of two or more different elements joined by chemical bonds

Matter Section 1

Compounds, continued

• Compounds have unique properties.

• Chemical formulas represent compounds.

– The following chemical formula represents the compound

for indigo:

Matter Section 1

Pure Substances and Mixtures

〉What is the difference between a pure substance and a mixture?

〉Elements and compounds are pure substances, but mixtures are not.

• pure substance: a sample of matter, either a single

element or a single compound, that has definite chemical and physical properties

• mixture: a combination of two or more substances

that are not chemically combined

Matter Section 1

Pure Substances and Mixtures,

continued • Mixtures are classified by how thoroughly the

substances mix. – heterogeneous mixture: substances aren’t mixed uniformly

and are not evenly distributed

– homogeneous mixture: substances are evenly distributed, and the mixture is the same throughout

– miscible: substances that can be mixed

– immiscible: substances that cannot be mixed

• Gases can mix with liquids.

Matter Section 1

Types of Mixtures

10.1 The Nature of Matter

Matter is a term used to describe anything

that has mass and takes up space.

Greek philosophers Democritus and

Leucippus proposed that matter is made

of tiny particles called atoms.

Atoms were an idea that few believed.

The first evidence was called Brownian

motion for Robert Brown, who first noticed

the jerky motion of tiny particles.

10.1 Elements

An element is a pure

substance that cannot be

broken down into other

substance by chemical or

physical means.

All of the matter you are

ever likely to experience

is made from one or more

elements in nature.

10.1 Elements

For example, water

can be broken down

into its elements,

hydrogen and oxygen,

when energy is added.

10.1 Atoms

A single atom is the smallest particle

that retains the chemical identity of

the element.

10.1 Compounds and elements

Compounds are two or more

different elements chemically

bonded together.

10.1 Examples of compounds

Compounds

contain more

than one type

of atom joined

together.

10.1 Molecules

A molecule is a group of two or

more atoms joined together

chemically.

10.1 Mixtures

Many substances

you encounter are

a mixture of

different elements

and compounds.

How many atoms are

in this mixture? How many molecules

are in this mixture?

10.1 Elements, compounds, and mixtures

Can you distinguish between atoms and

molecules in these images?

Matter Section 2

Physical Properties

〉Why are color, volume, and density classified as

physical properties?

〉Physical properties are characteristics that can

be observed without changing the identity of the

substance.

Matter Section 2

Physical Properties, continued • Physical properties can help identify substances. • Physical properties can be observed or measured.

– Examples: shape, color, odor, texture, state, melting point,

boiling point, strength, hardness, magnetism, the ability to conduct electricity or heat

– melting point: the temperature and pressure at which a

solid becomes a liquid – boiling point: the temperature and pressure at which a

liquid becomes a gas

• Physical properties help determine uses.

Matter Section 2

Physical Properties, continued

• Density is a physical property.

– density: the ratio of the mass of a substance to the volume of the substance

– common unit of density is g/cm3

• Density is different from weight.

massdensity ,

voor

lu

me

mD

V

Matter Section 2

Math Skills

Density

If 10.0 cm3 of ice has a mass of 9.17 g, what is

the density of ice?

1. List the given and unknown values.

Given: mass, m = 9.17 g

volume, V = 10.0 cm3

Unknown: density, D = ? g/cm3

Matter Section 2

Math Skills, continued

2. Write the equation for density.

density = mass/volume, or D = m/V

3. Insert the known values into the equation, and

solve.

D = 0.917 g/cm3

mD

V

3

9.17 g

10.0 cmD

Matter Section 2

Chemical Properties

〉Why are flammability and reactivity classified

as chemical properties?

〉A chemical property describes how a

substance changes into a new substance,

either by combining with other elements or by

breaking apart into new substances.

Matter Section 2

Chemical Properties, continued

• Flammability is a chemical property.

– flammability: the ability to burn

• Reactivity is a chemical property.

– reactivity: the capacity of a substance to combine

chemically with another substance

Matter Section 2

Chemical Properties, continued

• Physical and chemical properties are different.

– Physical properties can be observed without changing the identity of a substance.

– Chemical properties can be observed only in

situations in which the identity of the substance changes.

12.1 Properties of Solids

Different kinds of matter have

different characteristics.

Characteristics that can you

observe directly are called

physical properties.

Physical properties include

color, texture, density,

brittleness, and state (solid,

liquid, or gas). Ex. Iron is solid at

room temp.

12.1 Properties of Solids

A physical change is any change in

the size, shape, or phase of matter

in which the identity of a

substance does not change.

For example, when water is frozen,

it changes from a liquid to a solid.

12.1 Properties of Solids

Properties that can only be

observed when one

substance changes into a

different substance are

called chemical properties.

Any change that transforms

one substance into a

different substance is called

a chemical change. Ex. If you leave a nail

outside, it rusts.

12.1 Properties of Solids

The density of a solid

material depends on

two things:

1. the individual mass of

each atom or molecule,

2. how closely the atoms

or molecules are

packed together. Carbon atoms in

diamond are packed

very tightly.

12.1 Properties of Solids

Paraffin wax is also

mostly carbon, but its

density is only 0.87

g/cm3.

Paraffin’s carbon

atoms are mixed with

hydrogen atoms in

long molecules that

take up more space.

The density of paraffin is low

compared to diamond.

12.1 Properties of Solids

The atoms or molecules in a solid are

arranged in two ways.

1. If the particles are arranged in an

orderly, repeating pattern, the

solid is crystalline.

2. If the particles are arranged in a

random way, the solid is

amorphous.

12.1 Properties of Solids Metals don’t look

like “crystals”

because solid

metal is made

from very tiny

crystals fused

together in a

jumble of

different

orientations.

12.1 Mechanical properties

“Strength” describes the ability of a

solid object to maintain its shape even

when force is applied.

12.1 Mechanical properties

Tensile strength is a measure of how

much stress a material can withstand

before breaking.

12.1 Mechanical properties

Hardness measures a solid’s

resistance to scratching.

How might you compare the hardness of these two metals?

12.1 Mechanical properties

Elasticity describes a

solid’s ability to be

stretched and then return

to its original size.

Brittleness is defined as

the tendency of a solid to

crack or break before

stretching very much.

12.1 Mechanical properties

A ductile material can

be bent a relatively large

amount without

breaking.

The ductility of many

metals, like copper,

allow then to be drawn

into wire.

12.1 Mechanical properties

Malleability measures a

solid’s ability to be

pounded into thin

sheets.

Aluminum is a highly

malleable metal.

Matter Section 3

Physical Changes

〉Why is getting a haircut an example of a physical

change?

〉A physical change affects one or more properties of

a substance without changing the identity of the

substance.

• physical change: a change of matter from one form to

another without a change in chemical properties

Matter Section 3

Physical Changes, continued

• Physical changes do not change

a substance’s identity.

– Examples of physical

changes: cutting, crushing,

reshaping, changing state

• Dissolving is a physical

change.

Matter Section 3

Chemical Changes

〉Why is baking bread an example of a chemical change?

〉A chemical change happens when one or more substances are changed into entirely new substances that have different properties.

• chemical change: a change that occurs when one or more

substances change into entirely new substances with different properties

Matter Section 3

Chemical Changes

Matter Section 3

Chemical Changes, continued

• Chemical changes happen everywhere.

– Examples of chemical changes: burning, rusting, digesting, decomposing

• Chemical changes form new substances.

• Chemical changes can be detected.

– Signs include: change of color, change of smell, fizzing, production of heat, production of sound, production of light

• Chemical changes cannot be reversed by physical changes.

Matter Section 3

Breaking Down Mixtures and

Compounds

〉How can mixtures and compounds be broken down?

〉Mixtures can be separated by physical changes, but

compounds must be broken down by chemical

changes.

Matter Section 3

Breaking Down Mixtures and

Compounds, continued • Mixtures can be physically separated.

• Examples of separating a mixture:

– Separating saltwater into its parts by heating it: When the water

evaporates, the salt remains.

– Using a distillation device to heat a mixture whose components have different boiling points: The component that boils and evaporates first separates from the mixture.

– Using a centrifuge: The mixture spins rapidly until the components separate.

Matter Section 3

Breaking Down Mixtures and

Compounds, continued • Some compounds can be broken down through chemical

changes.

• Examples of separating a compound:

– When mercury(II) oxide is heated, it breaks down into the

elements mercury and oxygen.

– When a current is passed through melted table salt, the elements sodium and chlorine are produced.

– When you open a bottle of soda, carbonic acid in the soda breaks down into carbon dioxide and water.

10.3 Phases of Matter

On Earth, pure

substances are

usually found as

solids, liquids, or

gases.

These are called

phases of matter.

10.3 The phases of matter

A solid holds its

shape and does not

flow.

The molecules in a

solid vibrate in place,

but on average, don’t

move far from their

places.

10.3 The phases of matter

A liquid holds its

volume, but does

not hold its

shape—it flows.

Liquids flow

because the

molecules can

move around.

10.3 The phases of matter

A gas flows like a liquid,

but can also expand or

contract to fill a

container.

A gas does not hold its

volume.

The molecules in a gas

have enough energy to

completely break away

from each other.

10.3 The phases of matter

When they are close together,

molecules are attracted through

intermolecular forces.

10.3 The phases of matter

The forces in chemical bonds are

stronger than intermolecular

forces.

10.3 Intermolecular forces

Within all matter, there is a constant

competition between temperature and

intermolecular forces.

When temperature wins the

competition, molecules fly apart and

you have a gas.

When intermolecular forces win the

competition, molecules clump tightly

together and you have a solid.

10.3 Melting and boiling

The melting point is the

temperature at which a substance

changes from a solid to a liquid.

10.3 Melting and boiling

The temperature at which a liquid

becomes a gas is called the boiling

point.

Notice temperature is constant while ice melts!

10.3 Melting and boiling points of common substances

Materials have a

wide range of

melting and

boiling points.

10.3 Sublimation

Sometimes a solid

can change directly

to a gas when heat

energy is added.

This process is

called sublimation.