Physical Properties of Pure Substances

Intensive vs. Extensive

Essential Standard

• 6.P.2 Understand the structure, classifications and physical properties of matter.

Clarifying Objective

• 6.P .2.3 Compare the physical properties of pure substances that are independent of the amount of matter present including density, melting point, boiling point, and solubility to properties that are dependent on the amount of matter present to include volume, mass and weight.

Essential Question

• What is an INTENSIVE property of a pure substance?

• What is an EXTNESIVE property of a pure substance?

• What is the main difference between INTENSIVE & EXTENSIVE properties of pure substances?

Pure Substance

• A Pure Substance is a sample of matter that has the same COMPOSITION & CHEMICAL PROPERTIES

• All Elements on the Periodic Table & Water are pure substances

Periodic Table

Physical Properties

• A physical property of a substance is a property that can be seen without changing the substance into another substance

• Examples include…– Color– Luster (shiny)– Odor

Intensive Physical Properties• Intensive Physical Properties

are those properties that no matter what size will ALWAYS BE THE SAME

• Intensive Physical Properties include…① Solubility② Density③ Melting Point④ Boiling Point

Solubility

• Solubility is the ability of a substance to dissolve

• If the pure substance cannot dissolve it is said to be insoluble

• The faster a pure substance dissolves the more soluble it is

Solubility• Solubility is Intensive as it

does not matter how much of the substance you have it will either dissolve or it won’t (INTENSIVE)

• The speed of dissolving does not matter on how much of the substance you have it will still dissolve at the same speed

Solubility (Example)• If you stir a cup sugar in some

water it disappears into the water

• The sugar disappearing is the sugar DISOLVING making sugar soluble

• It doesn’t matter if you put 2 cups of sugar into water it will still dissolve

• KOOLAID

Density• Density is how COMPACTED

TOGETHER a substance is (not how much something weighs)

• A Bowling Ball is very dense because the atoms are COMPACTED TOGETHER

• A bulletin board made of cork is not very dense because the atoms are not packed close together

Density

• Density is INTENSIVE PHYSICAL property because it DOES NOT matter how much you have it will still have the same DENSITY

Density (Example)• Bulletin Board is not very dense

• The atoms are far apart for a solid

• You can put a pin or thumb tack into a bulletin board

• Now think of trying to put a pin or tack into a BOWLING BALL

• You can’t because bowling balls are too dense

Melting Point• Melting Point is the

temperature at which point a substance begins to melt

• It is INTENSIVE because it does not matter how much of the substance you have it will begin melting at the same temperature

Melting Point (Example)• Lets use gold as an example of a

substance

• I can use it because it is a pure substance that is on the Periodic Table

• No matter how much gold you have whether it be my wedding ring or a car made out of gold

• If you heat it to 1948 degrees it will begin to melt

Boiling Point

• Boiling Point is the temperature at which a substance begins to boil

• Boiling Point is INTENSIVE because it doesn’t matter how much of the substance you have it will start boiling when it hits its boiling point

Boiling Point (Example)• Lets use WATER as an

example

• Water will boil at 212 degrees

• It doesn’t matter if you have a cup of water or a bathtub of water as soon as it reaches 212 degrees it will start to boil

Extensive Physical Properties• Extensive Physical

Properties are those properties that DEPEND ON THE AMOUNT OF MATTER of the object

• Extensive Physical Properties include…① Volume② Mass③ Weight

Volume

• Volume is the AMOUNT OF SPACE that a solid, liquid or gas takes up

• Volume is EXTENSIVE as it DOES DEPEND on the amount of the sample

Volume (Example)• Lets use a cup & swimming

pool for an example

• Which one of these takes up more space

• The one that takes up more space will have a GREATER/BIGGER VOLUME (swimming pool)

Mass

• Mass is the amount of MATTER a substance contains & it never changes

• Mass is EXTENSIVE as it DOES DEPEND on how big the sample is

Mass (Example)• Lets us an elephant and a

baby as an example

• The larger the sample the LARGER/BIGGER the mass

• Because the elephant is bigger it will have more mass

• But don’t get confused it will have the same mass no matter where it is (Earth or Space)

Weight

• Weight is the FORCE OF GRAVITY on an object

• Weight is EXTENSIVE as it DOES DEPEND on where the sample is

Weight

• This means the more gravity in a place the more the substance will weigh (it will still have the same mass though)

• Weight will change depending on where the substance is because of GRAVITY

Weight (Example)• We will use Earth & the Moon as

an example

• Where will a person weigh more Earth or the Moon

• There is more GRAVITY pulling us to Earth because it is bigger it has a larger GRAVITATIONAL PULL

• This means we will WEIGH more there

EOG Questions• How does 250 mL of water compare to 500 mL of water?

• A) They have the same melting point but different boiling points.

• B) They have the same boiling point but different melting points.

• C) They have the same volume but different densities.

• D) They have the same density but different volumes.

Important Points• Properties of Pure substances

can be either INTENSIVE or EXTENSIVE

• INTENSIVE means that no matter how much or where the substance is the properties will be the same

• EXTENSIVE means that properties depend on either how big the sample is or where the sample is

• There are 4 INTENSIVE properties① Solubility② Density③ Melting Point④ Boiling Point

• There are 3 EXTNESIVE properties① Volume② Mass③ Weight