Physical vs. Chemical Properties

Part 1The study of matter

NC Essential Standards

• 8.P.1 Understand the properties of matter and changes that occur when matter interacts in an open and closed container– 8.P.1.1: Classify matter as elements, compounds, or mixtures based on how

the atoms are packed together in arrangements– 8.P.1.2: Explain how the physical properties of elements and their reactivity

have been used to produce the current model of the Periodic Table of Elements

– 8.P.1.3 Compare physical changes such as size, shape and state to chemical changes that are the result of a chemical reaction to include changes in temperature, color, and formation of a gas or precipitate.

– 8.P.1.4: Explain how the idea of atoms and a balanced chemical equation support the law of conservation of mass.

• 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?

Reviewing MATTER

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

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

Chemical Properties

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

Examples:

• flammability

• ability to rust

• reactivity with vinegar

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 = g/mL = g/cm3

• 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 mLD = 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.

Substance Density (g/ mL)

Mercury 13.6

Water 1.00

Ethanol 0.81

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 vs. Chemical Changes

Part 2

Concept of Change

• Change: the act of altering a substance

• Change of state/phase – Solid, Liquid, Gas

Physical Change

• Physical change: a change that occurs that does not change the identity of the substance– Melting ice– Freezing Kool-aid– Tearing paper– Boiling water

Chemical Changes

• Chemical change: a change that occurs that causes the identity of the substance to change– Burning– Digesting food – Reacting with other substances

• A chemical change is called a chemical reaction

Chemical Changes Cont’d

• Indicators of a chemical change:• Evolution of light• Evolution of heat• Evolution of a gas• Color change• Formation of a precipitate

– A precipitate is a solid substance that forms as a result of a chemical reaction

Is it Physical or Chemical?

Change Physical Chemical

Melting cheese

Burning wood

Milk souring

Wadding up paper

Bicycle rusting