Page 64 Nov. 5, 2012

Focus: Chemical and Physical Properties / Changes

Objective: pre-test, define physical and chemical property, physical and chemical change

HW: article, data – analysis - graph dueWarm-Up:• Is Humpty Dumpty falling off the wall

and cracking on the ground a physical or chemical change? • Explain your answer.

Pre-Assessment / Formative• Name

• November 5, 2012

• Block

• Title: Formative of Objectives 6.P.2.3, 6.P.3.1, 6.P.3.3

No more than 25 minutes

Homework pg. 63

• Science Fair Project

• Article and questions

• Bring back card for My Energy Kit

Physical versus Chemical Properties

• Matter: anything that has mass and takes up space– Mass – the amount of matter in something– Volume – the amount of space something

occupies

• Which of the following is matter?– A car?– A box?– You?

Reviewing MATTER

What is a property?

• Property: a characteristic of a substance that can be observed

http://www.gpb.org/chemistry-physics/chemistry/201

States, Boiling Point, Melting Point, and Solubility

Solid GasLiquid

Defining States of Matter

• States of matter are NOT defined by what they are made of.– Example: solids can be elements (gold), compounds

(Salt = NaCl), or mixtures (butter)

Element (Au) Compound (NaCl) Mixture (Milk, Salt, etc)

Defining States of Matter

• States of matter are defined by whether they hold SHAPE and VOLUME

Element (Au) Compound (NaCl) Mixture (Milk, Salt, etc)

ALL KEEP THE SAME SHAPE AND VOLUME = Solids

Defining States of Matter

• Solids – have a definite SHAPE and VOLUME.

Element (Au) Compound (NaCl) Mixture (Milk, Salt, etc)

ALL KEEP THE SAME SHAPE AND VOLUME

Particle View of a Solid

• Particles in a solid are PACKED CLOSELY together and they are in a FIXED POSITION.

Particles vibrate in place

Liquids

• Liquids – has definite VOLUME but no defined SHAPE

100 ml

Particle View of a Liquid

• Packed CLOSELY (like a solid), but move FREELY around each other (must stay in contact).

Gases

• Gases - do NOT have definite SHAPE or VOLUME.

Bromine gas fills up the entire volume of the container

Particle view of a Gas

• Particles can MOVE FREELY and will either fill up or squeeze into available space.

Changes in States of Matter

• Thermal Energy – heat energy.

• More thermal energy = More particle movement

Changing States

Solid GasLiquid

Increase Thermal Energy (Heat up)

Decrease Thermal Energy (Cool off)

Melting point

• Melting - change from solid to liquid• Melting point - SPECIFIC temperature when

melting occurs. • Each pure substance has a SPECIFIC melting

point.– Examples:– M.P. of Water = 0°C (32°F) – M.P. of Nitrogen = -209.9 °C (-345.81998 °F)– M.P. of Silver = 961.93 °C (1763.474 °F) – M.P. of Carbon = 3500.0 °C (6332.0 °F)

Melting Point

• Particles of a solid vibrate so fast that they break free from their fixed positions.

Solid Liquid

Increasing Thermal Energy

Melting point

Vaporization

• Vaporization – change from liquid to gas

• Vaporization happens when particles in a liquid gain enough energy to form a gas.

GasLiquid

Increasing Thermal Energy

Boiling point

Two Kinds of Vaporization

• Evaporation – vaporization that takes place only on the surface of the liquid

• Boiling – when a liquid changes to a gas BELOW its surface as well as above.

Boiling Point

• Boiling Point – temperature at which a liquid boils

• Each pure substance has a SPECIFIC boiling point.– Examples:– B.P. of Water = 100°C (212°F) – B.P. of Nitrogen = -195.79 °C (-320.42 °F)– B.P. of Silver = 2162 °C (3924 °F) – B.P. of Carbon = 4027 °C (7281 °F)

Boiling Point and Melting Point

Melting point

Boiling point

Solubility

• Maximum amount of a substance that can be dissolved in a liquid (at a specific temperature).

Salt (NaCl) Water (H20) at 20°C

Solubility

• Solute – substance being dissolved

• Solvent – liquid substance that solute is dissolved into

Salt (NaCl) Water (H20) at 20°C

Solubility

• Solute – ??????

• Solvent – ?????

Salt (NaCl) Water (H20) at 20°C

SaltWater

Solubility can change

• Increased Temp = Increased Solubility

• Different substances have different solubility curves

Solubility of Unknown Substance at different temperatures

0

0.5

1

1.5

2

2.5

3

1 3.8 6.6 9.4 12.2 15 17.8 20.6 23.4 26.2

temperature (degrees Celcius)

mg

of

un

kn

ow

n

su

bsta

nce/ m

l o

f H

20

Physical Property

Physical property: a property that can be observed without changing the identity of the substance.

Examples:

• luster

• malleability: the ability to be hammered into a thin sheet

• ductility: the ability to be stretched into a wire

• melting point

• boiling point

• density

• solubility

• specific heat

Special Physical Properties

• Melting point: the temperature at which a substance changes from a solid to a liquid at a given pressure

water = 0oC

• Boiling point: the temperature at which a substance changes from a liquid to a gas at a given pressure

water = 100oC

Chemical Properties

• Chemical property: a property that can only be observed by changing the identity of the substance

Examples:

•flammability

•ability to rust

•reactivity with vinegar

Chemical Properties & Physical and

Chemical Changes

Physical changes are those changes that do not result in the

production of a new substance.  If you melt a block of ice, you still

have H2O at the end of the

change.   

If you break a bottle, you still have glass.  Painting your nails will not stop them from being fingernails.  Some common

examples of physical changes are: melting, freezing,

condensing, breaking, crushing, cutting, and bending.

Some, but not all physical changes can be reversed. You could

refreeze the water into ice, but you cannot put your hair back together

if you don’t like your haircut!

Special types of physical changes where any object changes state, such as when water freezes or

evaporates, are sometimes called change of state operations.

CHEMICAL PROPERTIES

Chemical properties can ONLY be observed AS the substances are changing into different substances.

Chemical changes, or chemical reactions, are changes that result

in the production of another substance. 

FLAMMABILITY: A material’s ability to BURN in the presence of OXYGEN

REACTIVITY:How readily (easily) a substance combines chemically with other

substances.

When you burn a log in a fireplace, you are carrying out a chemical reaction that releases carbon.  When you light your Bunsen burner in lab, you are

carrying out a chemical reaction that produces water and carbon

dioxide. 

Common examples of chemical changes that you may be

somewhat familiar with are; digestion, respiration,

photosynthesis, burning, and decomposition. 

Physical or Chemical Change?

•Painting Wood

•PHYSICAL

Physical or Chemical Change?

•Burning Paper

•CHEMICAL

Physical or Chemical Change?

•Digestion of food

•CHEMICAL

Physical or Chemical Change?

•Sugar dissolving in water

•PHYSICAL

Physical or Chemical Change?

•Iron turning red when heated

•PHYSICAL

Physical or Chemical Change?

•Evaporation

•PHYSICAL

Physical or Chemical Change?

•A pond freezing in winter

•PHYSICAL

Physical or Chemical Change?

•Melting ice

•PHYSICAL

Physical or Chemical Change?

•Cutting wire

•PHYSICAL

Physical or Chemical Change?

•Painting fingernails

•PHYSICAL

Physical or Chemical Change?

•Cutting fabric

•PHYSICAL

Physical or Chemical Change?

•Baking muffins

•CHEMICAL

Physical or Chemical Change?

•Shattering glass

•PHYSICAL

Physical or Chemical Change?

•Decomposition of old leaves

•CHEMICAL

Physical or Chemical Change?

•Wrinkling a shirt

•PHYSICAL

Physical or Chemical Change?

•An old nail rusting

•CHEMICAL

Density

• Density is the amount of mass per unit of volume.

• Density can be used to identify a substance.

• The density of water is 1.0g/mL

Density Calculations

• Calculations:D = m/V = g/mL = g/cm3

• Ex: A cube has a mass of 2.8 g and occupies a volume of 3.67 ml. Would this object float or sink in water?

Mass = 2.8 g Volume = 3.67 mLD = 2.8g/3.67 mL= 0.76 g/mL

– This object would float in water because its density is less than water (1.0 g/mL).

More Density Calculations

• Ex: A liquid has a mass of 25.6 g and a volume of 31.6 mL. Use the table below to identify the substance.

Substance Density (g/ mL)

Mercury 13.6

Water 1.00

Ethanol 0.81

M=25.6 g V=31.6 mL

D = 25.6 g/31.6 mL

D= 0.81 g/mL

The substance is ethanol.

• Bingo

• clickr