Chemistry

UNIT 2 - MATTER

PHYSICALCHANGES

CHEMICALCHANGES

CHEMICAL CHANGES

• In a chemical change, a new substance or substances appear.

• Chemical changes are not reversible by normal methods.

PHYSICAL CHANGES

• In a physical change, the substance does not change.

• Physical changes can be reversed.

Examples of Physical Changes• Cutting a piece of paper:The shape has changed, but it is still paper.

• Boiling water:Water changes to steam. Steam is not a new substance; it is just a different form of water.

• Dissolving salt in water:It’s hard to tell whether a new substance forms when salt dissolves in water. If we evaporate

the water, we would get the salt back. That makes it a physical change, because it is reversible.

All changes of state are physical changes.• Water turning to ice or to steam is always a reversible

process. Ice and steam are not new substances. They are still the same water particles, just arranged a bit differently.

Examples of Chemical Changes• A chemical change will involve a chemical reaction.

• Cooking and burning are always chemical changes.

• A chemical reaction occurs when two or more chemicals combine to produce different chemicals.

• How can you identify a chemical change?- The color might change - Energy can be released- The smell might change- A gas may be produced- A precipitate may form

Question 1When a cloud forms in the sky, is it a physical or

a chemical change?

A) Physical change

B) Chemical change

Question 2Is rusting a physical or a chemical change?

A) Physical change

B) Chemical change

INTENSIVEPROPERTY

EXTENSIVEPROPERTY

An intensive property is one that does not depend on how much material is present.

For example, temperature is an intensive property. If a beaker of water has a temperature, all the waterhas the same temperature.It doesn’t depend on how muchwater there is.

Examples of intensive properties include:Temperature, density, chemical potential, viscosity, electrical resistivity,specific heat capacity, melting point and boiling point, pressure

An extensive property is one that does depend on the amount of substance.

So, mass and volume are both extensive properties. They both change if the amount of material changes. It is interesting to note thatdensity (defined as mass/volume) is an intensive property, but it is defined in terms of two extensive properties.

Examples of extensive properties include:Energy, mass, volume, weight, length

Question 1Which of the following is an intensive property?A) WeightB) EnergyC) Freezing pointD) Width

Question 2Which of the following is an extensive property?A) Freezing PointB) DensityC) TemperatureD) Width

Matter can be anything that occupies space and has mass.

State of Matter Solid Liquid Gas Plasma

Shape Definite Indefinite Indefinite Indefinite

Volume Definite Definite Indefinite Indefinite

Particle Movement

Packed closely together

More free to move

Move independently

Move independently

Examples DiamondsIce, Powder

Water, Milk, Coke

Helium, Hydrogen,

Sun, Plasma TV

Demonstration

Energy is increasingAll matter possesses a certain amount of energy. However, energy is not mass, as it cannot be weighed, and it does not occupy space.

Question 1What happens to a substance at the

temperature known as the melting point?A) It changes from a liquid to a gasB) It changes from a solid to a liquidC) It changes from a liquid to a solidD) It changes from a solid to a gas

Question 2"The shape of a liquid can change to fit the

container it fills." Is this statement true or false?

True or False

Question 3Which of the following statements applies to

gases?A) They have no fixed shape or form.B) Their atoms or molecules move

independently.C) Their atoms or molecules have lots of energy.D) All of the above.

Question 4Which of the following states of matter has the

least energy?A) SolidB) LiquidC) GasD) Plasma

PHYSICALPROPERTIES

CHEMICALPROPERTIES

Physical properties do not change the chemical nature of matter.

Physical Property Description Example

States of Matter changes

Energy increases/decreases to change solid to liquid to gas and vice versa

Draw the States of Matter Changes Triangle

Volume amount of space occupied Draw a graduated cylinder with liquid

Mass amount of matter it contains Draw the a triple beam

Density amount of mass per unit of its volumeD = m/v

Draw a marble inside a container of water

Compressibility extent that the volume of a substance will change in response to pressure.

Draw a hand squeezing a ball

Solubility amount of it that will dissolve in a liquid under certain conditions.

Draw Alkaselter dissolving in water

Specific Heat Capacity amount of heat energy thatis needed to raise the temperature of 1 kg of the substance by 1 K

Chemical properties are only visible in a chemical reaction.

A chemical property is one that will cause an irreversible change in a substance when it occurs.

Examples of chemical properties include: - sulfur burns in air - iron rusts in water - hydrogen peroxide decomposes to oxygen and

water - vinegar reacts with baking soda

Question 1Beeswax melts at 64° C. It is often used to make

candles. Why would it be impractical to make a cooking pot from beeswax?

A) Water boiled in a beeswax cooking pot wouldtaste badB) It would attract beesC) The beeswax would melt before the water

boiledD) It would be difficult to shape the beeswax

Question 2What is a substance's melting point usually the

same as?A) Its freezing pointB) The point at which it evaporatesC) Its boiling pointD) None of the above

MATTER

ELEMENTS

MIXTURESPURE SUBSTANCES

HETEROGENEOUS MIXTURES

HOMOGENEOUSMIXTURES

COMPOUNDS

Is the composition uniform?

Can it be decomposed by ordinary chemical means?

Can it be separated by physical means? YES

YES

YES

NO

NONO

MATTER

ELEMENTS

MIXTURESPURE SUBSTANCES

HETEROGENEOUS MIXTURES

HOMOGENEOUSMIXTURES

COMPOUNDS

Is the composition uniform?

Can it be decomposed by ordinary chemical means?

Can it be separated by physical means? YES

YES

YES

NO

NONO