Solids Ch. 12

3 Most Common Phases of Matter

Crystal Structure

Crystal Structure Metals, salts, and most minerals are made up of crystals! In 1912 physicists used x-rays to confirm that each crystal is a 3D orderly arrangement of atoms It took us quite awhile to actually see it!

Max von Laue Discovered that a beam of X-rays directed upon a crystal is diffracted, or separated, into a specific pattern X-ray diffraction patterns on photographic film show crystals to be neat, uniform lattices

Metals All metals contain a jumble of many crystals, each almost perfect, with the same regular lattice These metal crystals can be seen when a metal surface is etched, or cleaned with acid

Amorphous

Amorphous Solids Noncrystalline solids are amorphous Atoms and molecules in a solid are distributed randomly Rubber, glass, and plastic all lack an orderly, repetitive arrangement at a molecular level You can tell because rubber is elastic, glass flows when stressed

4 Principal Types of Bonding in Solids Atoms are tied together by electrical bonding forces. For solids this includes: Ionic Covalent Metallic Van der Waals’ Which of these is weakest?

Mini Quiz How does the arrangement of atoms in a crystalline substance differ from that in a noncrystalline substance? What evidence can you cite for the microscopic crystal nature of certain solids? 3) For macroscopic crystal nature of certain solids?

Density Depends how much of Each you have! Iron is denser though Is iron heavier than wood? Depends how much of Each you have! Iron is denser though

Density The masses of the atoms and the spacing between them determine the density of materials A measure of the compactness of matter, OR how much mass occupies a given space OR the amount of mass per unit volume

Density Formula

Density The density is a property of a material Therefore it doesn’t matter how much of the material you have Density of a material depends upon the masses of the individual atoms that make it up and the spacing between those atoms

Units for Density g/cm3 When we do weight density then we use N/m3 1cm3 = 1mL When we do weight density then we use N/m3 because a 1kg body has a weight of 9.8N, weight density is numerically 9.8 x mass density

Mini Quiz Is iron or wood heavier? Explain! Density is a ______________ of a material. This means it doesn’t depend on how much of the material you have. What is one of the correct units we might use for density?

Elasticity When an object is subjected to external forces, it undergoes change in size, or shape, or both. The change depends on the arrangement and bonding of the atoms in the material Example: A spring can be stretched or compressed by an external force

Inches and pounds… yuck who even uses those? Elasticity A weight hanging on a spring stretches the spring Additional weight stretches the spring ___________ Further Inches and pounds… yuck who even uses those?

Elasticity If the weights are removed, the spring returns to its original length We say that the spring is elastic

Examples of Elasticity When a batter hits a baseball, the bat temporarily changes the ball’s shape An archer, about to shoot an arrow, first bends the bow, which springs back to its original shape when the arrow is released.