# Physical versus Chemical Properties

## Presentation on theme: "Physical versus Chemical Properties"— Presentation transcript:

Physical versus Chemical Properties
Chapter 2 Section 2 Describing matter

Reviewing MATTER 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?

What is a property? Property: a characteristic of a substance that can be observed

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

Physical Properties Color Shape Size Density Melting Point
Boiling Point

Example of Physical Property
The physical properties of sodium metal can be observed or measured. It is a soft, lustrous, silver-colored metal with a relatively low melting point and low density. Hardness, color, melting point and density are all physical properties.

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

Thermal Density Solubility State Ductility Malleability

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

Chemical Properties Examples of Chemical Properties
Reactivity with oxygen Nonreactivity with oxygen Flammability Nonflammability

Chemical Properties

Comparison of Physical and Chemical Properties

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 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 mL D = 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. M=25.6 g V=31.6 mL D = 25.6 g/31.6 mL D= 0.81 g/mL The substance is ethanol.

Physical Change Physical change is the change that affects one or more physical properties of a substance. Imagine breaking a piece of chalk into two pieces. What are you changing? What is not being changed? Physical changes do not change the identity of the matter involved

Physical Change Freezing water for ice cubes Sanding a piece of wood
Cutting your hair Crushing an aluminum can Bending a paper clip Mixing oil and vinegar

Chemical Change Chemical change happens when two or more substance are changed into one or more new substances with different properties. Properties of a substance describe which chemical changes will or will not happen Chemical change and properties are not the same, a change is the process in which it changes

Chemical Change Examples of Chemical Changes Soured milk
Effervescent tablets Statue of Liberty Baking a cake

Chemical Change Clues that chemical change has occurred
Changes in color Heat Fizzing and foaming Production of sound or light