Today we are going to be looking at the properties of -

1. Today we are going to be looking at the properties of - Solids

2. Different types of solids have different characteristics. Today we will be breaking down those characteristics that are associated with the solid state of matter. • One of the first characteristics that we are going to be looking at is that of Density. • Earlier in this unit we learned about two ways to measure matter. • Those being the amount of Mass that it had and the amount of space or Volume that it occupied. • Density is a property that describes the relationship between these two measurements. • This is shown by the following equation – Density = Mass / Volume (g/cc) = (g) / (cc)

3. What you are doing when you are measuring the density of an object is you are taking a sample of its volume, whether it is in mls or in cc and dividing by the mass of that sample. • It is very important to note that this formula will work with only Homogeneous materials or Substances! • Remember these types of materials are the same throughout the sample! • So no matter how large or small the density will be the same throughout. • Samples that are Heterogeneous will not be the same throughout. You cannot use this formula to find the density of Heterogeneous materials. • Their densities will differ from location to location.

4. Like I said before not all solids will have the same properties! • Some solids have more material packed into their structure than others. • That is to say, they both have a certain density, but some solids have more matter squeezed into an area than something else of the same volume has. • For example, there is an old riddle that states, “Which weighs more, a pound of lead or a pound of feathers?” • A lot of people answer quickly without thinking that it is the pound of lead because they are thinking of the density of the object. • Obviously a pound of lead makes a much smaller volume than a pound of feathers. • Even though they both weigh the same!

5. All solids exhibit Hardness to a certain degree. • By hardness we are measuring the solid’s resistance to scratching. • Geophysicist's have come up with a way to determine the hardness of a solid. • It’s called the Moh’s scale of hardness. • It runs from one to ten with ten being the hardest and one the softest. • Diamond is the hardest and talc is the softest • The scientists use trial and error to determine the “Scratchability” of the solid in question.

6. 1 2 3 4 5 6 7 8 9 10 Scratched by finger nail Scratched by steel knife Will scratch glass - gemstones Talc Gypsum Calcite Fluorite Apatite Moonstone Quartz Topaz Corundum Diamond The Mohs Scale of Hardness measures a substance's hardness, that is, how resistant that substance is to being scratched. This scale was invented by Austrian mineralogist Friedrich Mohs (1773-1839).

7. All solids show a certain degree of Elasticity. • Elasticity is the measure of a solid’s ability to be stretched and then return to its original size. • This gives the solid the ability to bounce and withstand an impact without breaking. • Ever hear a “Thumpin” stereo in someone’s car? • I’m sure you’ve not only heard it but felt it as well. The sound waves from the speakers are transferred through the solid metal of the car and then released out into the air where you can hear it. • If the metal of the car wouldn’t have the elasticity that it does, the sound waves would shatter it! • Longitudinal and Transverse Wave Motion

8. Whereas all solids can be stretched to a certain limit, they can also break. • Brittleness measures a material’s tendency to shatter upon impact. • All rocks break. • They break because they have reached their elastic limit and shatter. • This is because the amount of stretch that they have is very small, and when they reach the point at which they can no longer bend, they break or shatter. • If you saw what happened at the I-280 Bridge failure you could see that not only did the steel stretch, but it also shattered! • This tendency is best shown in nature when an earthquake occurs. • The rock’s stick together and stretch until they all of sudden break and move past each other.

9. Indian Ocean Earthquake and Tsunami

10. Certain solids are more Malleable than others. • Malleability is a measure of a solid’s ability to be pounded into thin sheets. • Obviously a rock isn’t very malleable, but aluminum is. • Without this characteristic, we wouldn’t have the things that use metal. • Almost all metals are very malleable. • Some however are engineered so that they aren’t • Elmore Ohio has a plant that works with a metal called Beryllium. It is very lightweight and resists deformation. This is why it is used in the aerospace industry. The only problem is that it is very carcinogenic.

11. Some solids are used specifically because they do have a certain degree of stretch and strength. • Tensile Strength is a measure of how much pulling, or tension, a material can withstand before breaking. • Steel cables and ropes have certain degrees of this characteristic. • Believe it or not, when you look at a simple ratio of strength to weight, nothing has more tensile strength than spider web. • Scientists are currently trying to find out how the silk from a spider gets its strength. • Find the answer to that one and the possibilities are endless! • Understanding Earthquakes: Elastic Rebound Animation

12. To wrap things up we now know that all solids show the following characteristics. • They have Density • A ratio of mass to volume. • They have Hardness • The ability to resist scratches. • They are Elastic • The ability to stretch and return to its original shape. • They are Brittle • The tendency to shatter upon impact. • They are Malleable • The ability to be pounded into thin sheets • They have Tensile Strength • A measure of how much pulling they can withstand without breaking.