Physical properties Chapter 2 Section 2
Physical Properties? Characteristics of matter that can be observed or measured without changing the identity of the matter. Some can be easily described through observation: Color, Shape, Odor, Texture, Size, State Others can help ID how to use the matter: Magnetism, Electrical Conductivity, Strength, Flexibility
Physical Properties (cont’d) Thermal Conductivity – the rate at which a substance transfers heat. Ex. – Plastic foam is a poor conductor, Aluminum is a good conductor.
Solubility – the ability of a substance to dissolve in another substance. Ex. – Kool-Aid and Sugar dissolve in water.
Ductility – the ability of a substance to be pulled into a wire. Ex Ductility – the ability of a substance to be pulled into a wire. Ex. – Copper is often used in wiring because it is ductile.
Malleability – the ability of a substance to be rolled or pounded into thin sheets. Ex. – Aluminum can be rolled into thin sheets to make foil.
State – the physical form in which the substance exists. Ex. – Solid, Liquid, or Gas. Includes Melting Point, Boiling Point, and Freezing Point
Density – the amount of mass in a given space, or volume Density – the amount of mass in a given space, or volume. (solid or liquid) Ex. – Lead is very dense, so it makes a good sinker for a fishing line.
Liquid Layers
Liquid Density - Liquids have density … liquids are matter. - Layers can be formed when liquids are poured into a container. layers are based on the density of the liquid. The most dense layer is at the bottom. The least dense layer is at the top. The order of the layers show the order of increasing density. AIR behaves like a liquid
Would you rather carry around a 1 pound of feathers or 1 pound of lead?
Density of Solids Knowing the density of a solid can tell you how much space an amount of an object will take up. Knowing the density of a solid can also tell you if the solid will float or sink in water.
Will it float or sink? If an object has a density > water, it will sink when placed in water. If an object has a density < water, it will float. Water = “1” (1 gm/cm3) https://www.youtube.com/watch?v=aR0b4QRhfU0
Density = Mass Volume Density = 35g = 11.36g/cm3 3.08cm3 Ex: A piece of lead has a mass of 35g and a volume of 3.08cm3. What is the density of the lead? Density = 35g = 11.36g/cm3 3.08cm3 Units for Density Solids = g/cm3 or kg/m3 Liquids = g/mL
Using Density to ID Substances every substance has a density that is different from other substances. Densities of Common Substances Substance State Density g/cm3 Water Vapor Gas 0.000804 Helium 0.0001663 Oxygen 0.001331 Water Liquid 1.0 Cooking Oil 0.92 Mercury 13.55 Gold Solid 19.3 Pyrite (Fool’s Gold) 5.02 Lead 11.35 Ice
Physical Changes a change that affects one or more physical properties of a substance. A physical change does not change the matter of the substance and does not form a new substance. Physical changes can often be reversed.
CHEMICAL properties Chapter 2 Section 3
What is happening to the car and why?
Chemical Property def: a property of matter that describes a substance’s ability to participate in chemical reactions. describe a substance based on its ability to change into a new substance with different properties. NOT as easy to observe with your senses as physical properties.
Chemical Properties (cont’d) Flammability – the ability of a substance to burn. combustibility
REACTIVITY – the ability of 2 or more substances to combine & form 1 (or more) new substances. Ex: Rust created by metal + oxygen
Chemical Changes = new things! - chemical change occurs when 1 or more substances are changed into entirely new substances with different properties and composition.
Clues to Chemical Changes - Color change - Fizzing or bubbling (gas production) - Heat is created - Production of light, sound or odor - Chemical changes are usually not reversible.
differences Physical chemical Composition / Identity stays the same (so, many changes are easily reversed) Composition /Identity changes (so, most changes are not easily reversed)