Chemical and physical change

PHYSICAL PROPERTIES OF MATTER

What are Properties used to describe parts of the car?

Some Physical Properties

• Hardness Odor• Color Texture• Density State of matter• Strength• Flexibility (malleable, ductile)• Shape• Melting point, boiling point• Ability of conduct electricity

What is a physical property?

• Any characteristic that can be used to describe matter

• Often very easy to observe

Melting/Boiling/Freezing points

The temperatures when an object changes it’s state of matter

Definitions of Melting, Boiling, Freezing points

• Boiling point: the temperature at which a liquid becomes a gas, or vice versa

• Melting point: the temperature at which a solid becomes a liquid

• Freezing point: same as melting point, but used when the temperature is cooling (decreasing)

Instances, examples

What is freezing point of water?

What is the boiling point of water?

The numbers• Freezing point: 32°F or 0°C• Melting point: 212°F or 100°C

• How to convert Fahrenheit to Celsius: C=5(F-32)/91. Begin by subtracting 32 from the Fahrenheit number. 2. Divide the answer by 9. 3. Then multiply that answer by 5.

Here's an example: Change 95 degrees Fahrenheit to Celsius: 95 minus 32 is 63. Then, 63 divided by 9 is 7. Finally, 7 times 5 is 35 degrees Celsius.

PHYSICAL CHANGE IN MATTER

Possible evidence of physical change

• Alteration of any physical feature– Length– Shape– Color

• Application of force which changes the object– Pounding– Tumbling– stretching

Changes in matter

• Physical Change

1. Does not change a substance identity (chemical makeup, formula)

2. Does change at least one physical property3. Dissolving is a physical change4. Changing the state of matter is a physical change5. Separation of a mixture into its ingredients is a

physical change

Examples of physical changes in matter

• Hair Cut• Breaking Chalk• Crushing an aluminum

can

Dissolving is a physical change

CHEMICAL PROPERTIES OF MATTER

What chemical changes have occurred?

Definition of chemical property

• A property of matter that describes the substance’s ability to participate in chemical reactions

• A chemical property describes how a substance interacts with the materials in the surrounding environment to form new compounds or elements.

Examples of Chemical properties

ReactivitySulfuric acid andSugar

FlammabilityCarbon Compounds in wood, oxygen in the air and an igniter

Sulfuric Acid and Reactivity Demo

REACTIVITYChemical Property

Reactivity

• The ability of a substance to combine chemically with another substance and form new or different compounds

FLAMMABILITYChemical Property

Flammability

• The ability of a substance to react in the presence of oxygen and burn when exposed to heat energy

CHEMICAL CHANGE

Chemical changeOccurs when 1 or more substances react to form new

substances with different properties

• Chemical Properties can only be detected when a change occurs

• Chemical changes can be detected

• Chemical changes cannot be reversed by physical changes

• Compounds can be broken down through chemical changes

Possible evidence of chemical change…

• Change in texture• Change in smell• Something bubbles or fizzes• Changing color

Chemical change

• CO2 Gas made by combining Sodium Bicarbonate (NaHCO3) and water (H2O)

Results when combining baking soda and with vinegar

• Vinegar and baking soda chemically react, creating new compounds:

• CO2 (g) + NaC2H3O2 (aq) (sodium acetate)

Chemical reactions

• Magnesium reaction with water

Chemical reaction betweensodium and water

Important Note

• The ability not to react with other substance or not burn is also a chemical property

EXAMPLES OF NON-REACTIVE MATERIALS

Elements with non reactive properties

• Gold • Argon Gas in Light Bulb

                        

        

Galvanized steel is steel coated with zinc

• Not galvanized • Galvanized nails

Another use for non-reactive materials

• Dentures, False Teeth, Replacement teeth made from acrylic plastic.

• Nontoxic, hard, water proof, unreactive, and affordable

Comparing Physical and Chemical properties

1. You can observe physical properties with no visual change substance (the car is red)

2. Observation of chemical properties only occurs when the substance changes (the car is rusting)

3. A physical change in a material does NOT require a change to its chemical identity. A chemical change does

List a Physical and Chemical property of various materials below:

Substance Physical P Chemical PHeliumWoodBaking SodaPowdered SugarIronWater

CHARACTERISTIC PROPERTY

Characteristic properties

• Most useful in identifying and classifying substances

• Can be both physical and chemical

• Examples are a substance’s density, melting point, solubility, and reactivity

IS IT BAKING SODA OR POWDERED SUGAR?

How chemical reactions can be used to determine identity of substance

• Both baking soda and powdered sugar are white powders

• Baking soda reacts with vinegar• Sugar does not