Describing Matter

Physical Properties Physical properties of matter can be observed or measured without changing the identity of the matter.

State The physical form in which a substance exists, such as a solid, a liquid or a gas Ice is water in its solid state

Malleability The ability to be pounded into thin sheets example Aluminum foil

Tensile strength is a measure of how much stress a material can withstand before breaking.

Solubility The ability to dissolve in another substance Sugar dissolves in water

Hardness Hardness measures a solid’s resistance to scratching.

Elasticity describes a solid’s ability to be stretched and then return to its original size. Brittleness is defined as the tendency of a solid to crack or break before stretching very much.

A ductile material can be bent a relatively large amount without breaking. The ductility of many metals, like copper, allow then to be drawn into wire.

Density D=M V Units- g/mL g/cm3 kg/m3 kg/L

Thermal (Heat) Thermal Conductivity -Is the rate at which a substance transfers heat Thermal Expansion-the tendency of atoms or molecules in a substance to take up more space as the temperature increases.

Physical Changes Do not change the identity of a substance and are sometimes easy to reverse Examples:butter can be melted and then it can be put in the refrigerator to reverse the change Water can be frozen and then melted

More Examples of Physical Changes Melting ice cubes Sanding a piece of wood Cutting hair Crushing a can Bending a paper clip Mixing oil and vinegar

12.1 Properties of Solids Properties that can only be observed when one substance changes into a different substance are called chemical properties. Any change that transforms one substance into a different substance is called a chemical change.

Chemical Properties Flammability Reactivity (with water, acid, or oxygen) Electrolysis

Chemical Changes Any time there is a chemical change, a chemical reaction has occurred.

CLUES TO CHEMICAL CHANGES Bubbling - a new gas is formed Turns cloudy- a precipitate is formed A precipitate is a solid that is insoluble in the reaction mixture

CLUES TO CHEMICAL CHANGES Change in color – a new substance is forming Change in temperature – energy is being released or absorbed

Types of Solids The atoms or molecules in a solid are arranged in two ways. If the particles are arranged in an orderly, repeating pattern, the solid is crystalline. If the particles are arranged in a random way, the solid is amorphous.

Examples Amorphous Rubber Wax Glass plastics Crystalline Salts metals