CHAPTER 15 SECTION 2

Properties of Matter

Look but don’t touch! A physical property is any characteristic of a

material that you can observe without changing the identity of the substance.ColorSizeShapeDensityMelting pointBoiling point

When you describe the appearance of an object, you are describing/measuring the physical properties of that object.

Behavioral Issues Some physical properties help to

describe the behavior of a material.MagnetismConductivityViscosityDensity

Don’t make me separate you! We can take advantage of

physical properties to separate a specific material from a mixture. How would you separate a mixture of

sunflower seeds and poppy seeds? How would you separate a mixture of

metal shavings and saw dust? How would you separate dirt from

mud? How would you separate alcohol

from wine?

Don’t lose your identity! When a material freezes, boils, evaporates, or

condenses, it undergoes a physical change. These physical changes can mean a change in size,

shape or state of matter. What are the states of matter?

SolidLiquidGasPlasma

These changes may involve a change in energy, but the kind of substance or identity of the element or compound does NOT change.

I said, don’t make me separate you!

Distillation is the process of separating a substance from a mixture through the use of evaporation and re-condensation.

If a mixture has two different liquids with different boiling points, one liquid can be removed from the other by heating the mixture.

The liquid with the lower boiling point will evaporate, leaving the second liquid behind.

Distillation is used in the extraction of oils from plants and in the liquor industry.

Physical Changes can be reversed!

Ice melts into liquid water and can be re-frozen.Melting & Freezing

Liquid water can be boiled into steam and can condensed back to liquid water.Evaporation & Condensation

Dry Ice can sublimate from solid to carbon dioxide gas and deposit back to dry ice.Sublimation & Deposition

Chemical Properties and Changes

A chemical property is a characteristic of a substance that indicates whether it will undergo a chemical change.FlammableCorrosiveOxidizerPhotosensitive

Chemical Changes

A chemical change occurs when one substance changes into another substance.Elements will NOT change into

other elements!!!○ This is called alchemy!

It is possible for one compound to change into another compound.○ This is called chemistry! Nicolas Flamel

Ugh, what’s that smell?

Indicators that a chemical change has occurred:A change in smellThe release of a gas or vaporA change in colorA change in temperatureThe formation of a precipitate

Of course the only true way to know that a chemical change has occurred is when a new substance is produced.

The Bog of Eternal Stench!

Evidence of Chemical Changes

Okay you two, separate! We can also use chemical

changes to separate materials. Many businesses involved in

mining, will use chemicals reactions to separate metals from the ore that they are trapped in.

These chemical reactions involve chemical changes that separate the metal from the rock.

Chemical Changes CANNOT be reversed

Physical and Chemical Changes in Nature Our great planet creates many

different weather conditions. Some of these weathering

effects cause physical changes to the Earth’s surface.

Other weathering effects cause chemical changes to the Earth’s surface.

What examples of each can you think of?

Keep track of your Mass! The law of conservation of mass,

states that matter cannot be created or destroyed. It simply exists.

It can be rearranged or moved around.

This means that the mass involved in any kind of physical change or chemical change MUST be conserved.

Mass Before Change = Mass After Change

Let’s review!

The following are examples of Physical and Chemical changes. Use what you have learned to tell what kind of change is occurring in each.

Examples1. A wood log burns in a fireplace and turns to smoke and ash.

2. An ice cube is dropped into a hot fry pan where it flash evaporates.

3. Salt is dissolved into water.

4. Sugar is dissolved into water.

5. Little Suzy uses a boxed cake mix with water, eggs and oil to bake a cake.

6. Little Johnny dissolves a nail in acid.

7. Rain water flows through a valley carving away rock and soil.

8. Rain water soaks through the soil and dissolves limestone deposits to create a cave.

9. Lighting a candle.

10. Rust on a car.

Great Job!

Now we will work on a concept comparison routine!