Physical and Chemical Properties Physical and Chemical Changes

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Physical and Chemical Properties. Physical and Chemical Changes What does the object look like?

Physical and Chemical Properties. Physical and Chemical Changes What does the object look like? How does the object change?

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

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

Physical Property Physical property: a property that can be observed without changing the identity

Physical Property Physical property: a property that can be observed without changing the identity of the substance. • luster: shininess or dullness • malleability: the ability to be hammered into a thin sheet • ductility: the ability to be stretched into a wire • melting point • boiling point • density

Special Physical Properties l Melting point: the temperature at which a substance changes from

Special Physical Properties l Melting point: the temperature at which a substance changes from a solid to a liquid at a given pressure water = 0 o. C l Boiling point: the temperature at which a substance changes from a liquid to a gas at a given pressure water = 100 o. C

Density l Density is the amount of mass per unit of volume. l Density

Density l Density is the amount of mass per unit of volume. l Density can be used to identify a substance. l The density of water is 1. 0 g/m. L

Density Calculations l Calculations: D = m/V = g/m. L = g/cm 3 l

Density Calculations l Calculations: D = m/V = g/m. L = g/cm 3 l Ex: A cube has a mass of 2. 8 g and occupies a volume of 3. 6 ml. Would this object float or sink in water? Mass = 2. 8 g Volume = 3. 6 m. L D = 2. 8 g/3. 6 m. L= 0. 78 g/m. L u This object would float in water because its density is less than water (1. 0 g/m. L).

Chemical Properties l Chemical property: a property that can only be observed by changing

Chemical Properties l Chemical property: a property that can only be observed by changing the identity of the substance Examples: • Combustibility (flammable) • Ability to rust • Reactivity

What is Change? l. Change: the act of altering a substance

What is Change? l. Change: the act of altering a substance

Physical Change l Physical change: a change that occurs that does not change the

Physical Change l Physical change: a change that occurs that does not change the identity of the substance u Melting ice(change in state or phase) u Freezing Kool-aid u Tearing paper u Boiling water (same as melting ice) u Change of State

Chemical Changes l Chemical change: a change that occurs causing the identity of the

Chemical Changes l Chemical change: a change that occurs causing the identity of the substance to change u Burning u Digesting food u Reacting with other substances l A chemical change is called a chemical reaction

Chemical Changes Cont’d l Indicators of a chemical change: • Color change • Precipitation

Chemical Changes Cont’d l Indicators of a chemical change: • Color change • Precipitation • Gas production • Temperature change • Changes in characteristic properties (odor, light given off, etc. )

Precipitation l Precipitation – the solid that forms from a solution during a chemical

Precipitation l Precipitation – the solid that forms from a solution during a chemical reaction. l It looks like a cloudy solid in an otherwise clear solution.

Is it Physical or Chemical? Change Melting cheese Burning wood Milk souring Wadding up

Is it Physical or Chemical? Change Melting cheese Burning wood Milk souring Wadding up paper Bicycle rusting Mixture Physical Chemical