Chapter 3 Physical & Chemical Changes. Properties of Matter Physical Properties are characteristics of a substance that can be observed without changing.

Chapter 3Physical & Chemical Changes

Properties of Matter

• Physical Properties are characteristics of a substance that can be observed without changing the identity of the substance.– Ex. Wood is wood whether it is in a house, a

toothpick or a baseball bat.

• Physical Properties that you already learned about:– Mass– Volume– Density– Weight– Also, color, texture, hardness, shape, etc.

Section 1 - Another Important Physical Property of Matter that we need to

study is the…•Phases of Matter• There are 4 phases of matter:

– Solid– Liquid– Gas– Plasma

Section 1 - Solids

• Have a definite shape and a definite volume

• Particles (molecules) are packed very close together so no movement can occur except vibrations.

• 2 types– Crystalline solids have particles arranged in

regular repeating patterns, ex table salt, quartz– Amorphous solids have particles that aren’t

arranged in a rigid way, so they can flow slowly, ex – candle wax, silicone rubber.

Section 1 - Liquids

• Do not have definite shape, but do have a definite volume

• Particles are close together, but not as close together as a solid.

• The particles can move past one another, thus allowing it to flow.

• They take the shape of the container they are in.

• One important Property of liquids is viscosity– Viscosity – the resistance of a liquid to flow;

ex honey has a higher viscosity than water.

Section 1 - Gases

•Do not have definite shapes or volumes.

•Particles are very far apart and move very freely.

Section 1 - Plasma

• Extremely high in energy and temperature.

• Matter becomes so hot that the electrons separate from the nucleus.

• Plasma is rare on earth (ex. lightning & parts of flames), but is the most common form of matter in the universe because….

• Stars are made of plasma and stars are quite common.• NOTE: Plasma TV’s ARE NOT made of

Plasma!!!!

Section 1 – More About Gases

• 2 scientists studied how gases behave in relation to pressure and temperature.

• Boyle’s Law – pressure & volume are inversely (indirectly) related– The higher the pressure, the lower the

volume.– The lower the pressure, the higher the volume

• Charles’ Law – temperature & volume are directly related– The higher the temperature, the higher the

volume– The lower the temperature, the lower the

volume

Section 1 – Gas Laws

• Boyle’s Law – pressure & volume are inversely (indirectly) related

P1 = V2P2 V1

• Charles’ Law – temperature & volume are directly related

V1 = V2T1 T2

• If 50 mL of oxygen gas is compressed from 20 atm of pressure to 40 atm of pressure, what is the new volume? (assume constant temp)

GIVEN:

V1 = 50 mL

V2=?

P1 = 20 atm

P2 = 40 atm

WORK:P1 = V2P2 V120 atm = V240 atm 50 mL1000 atm mL = 40 atm (V2) 40 atm 40 atmV2 = 25 mL

Section 1 – Using the Gas Laws

• A gas occupies a volume of 100 mL at 300° C. At what temperature will the gas have a volume of 200 mL?

GIVEN:

V1 = 100 mL

V2= 200 mL

T1 = 300° C

T2 = ?

WORK:V1 = V2T1 T2100 mL = 200 mL300° C T2100 mL (T2) = 60,000° C mL 100 mL 100 mLT2 = 600° C

Section 1 - Using the Gas Laws

Section 2 - Phase Changes

• Phase changes are caused by adding or taking away thermal energy

• Thermal energy is fancy schmancy word for HEAT!!!!!!

• Phase changes of matter are called:– Melting– Freezing– Vaporization– Condensation– Sublimation

Section 2 - Phase Changes cont’d

• Phase changes are Physical Changes• This is because the substance is

changes its form, but it is not changing the kind of substance it is chemically.– Ex – water (H2O) is still water whether it

is in an ice cube, liquid water or water vapor)

Section 2 - Solid – Liquid Phase Changes

• Melting - Solid to Liquid– Melting point – temperature at which

a substance will melt

• Freezing – Liquid to Solid– Freezing Point – temperature at which

a substance will freeze.

• The melting point of a substance is the same temperature as its freezing point!!

Section 2 - Liquid - GasPhase Changes

•Vaporization – Liquid to Gas•2 kinds:

–Evaporation – Liquid to Gas only at the surface of liquid

–Boiling – Liquid to Gas in the entire liquid•Temperature at which a substance boils is the boiling point

Section 2 - Gas - LiquidPhase Changes

•Condensation – Gas to Liquid–The gas molecules lose thermal energy (heat) and slow down. Then, as they come together, they join to form a liquid.

Section 2 - Solid - GasPhase Changes

•Sublimation – Solid directly to Gas –Examples

•Solid carbon dioxide (dry ice) changes directly into a gas

•Moth balls

As you move to the right, is heat being added to or given off by

the substance?

As you move to the right, what is happening to the space between the molecules?

As you move to the left, is heat being added to or given off by

the substance?

As you move to the left, what is happening to the space between the molecules?

What temperature is this if this substance is water?

What temperature is this if this substance is water?

Let’s Review for a Moment…

•Phase of matter, color, shape, hardness, mass, volume, density were all what kind of properties of matter?

•PHYSICAL PROPERTIES!!! Right……

Section 3 - Physical Properties - Definition

•Physical Properties – properties of matter that can be observed using the senses without changing the identity of a substance.

•What kind of property would describe a change of matter into another substance?

Section 3 - Chemical Properties and Changes

• Chemical Properties – the properties that describe the ability of a substance to change into a different substance.–Flammability – the ability to burn

•Ex wood is flammable–Supporting burning – the ability of a substance to be used during burning.•Ex – oxygen is needed for wood to burn but the oxygen itself doesn’t burn.

Section 3 - Chemical Properties and Changes

•Chemical changes (aka chemical reaction) – the process by which a substance changes into another substance by chemical means.–Ex: cars rusting, wood burning, yeast changing sugar into gas in bread, cheese aging, leaves changing color…

Classify the following as either a physical or chemical change….

• An ice cube cracking• Carving a piece of marble into a statue• Burning wood• Wax melting• Sugar dissolving in tea or coffee• Pop rocks releasing carbon dioxide into

your mouth• Leaves changing colors in the fall