3 Properties of SolidsDensity- describes the relationship b/t mass and volume of homogenous material- tells how tightly molecules are “packed”Formula: D=m/vWhat are the units of density?Density stays the same no matter how large or small the sample isHeterogenous materials may not have the same density throughout
4 Ideas from lab 17.1 Density does not depend on size of the material Density does depend on the type of materialDensity does not depend on the shape of the material (unless you have altered volume)Density does depend on the state of matter
5 Other properties Hardness-resistance to scratching Elasticity-ability to stretch then return to original shapeBrittleness-tendency to shatter on impactMalleability- ability to be pounded into sheetsTensile strength- measures how much tension a material can withstand without breaking
6 Density of FluidsFluid- matter with the ability to flow (applies to gases too)The liquid form of a material is usually less dense than the solid form of a material- Why?As temperature increases, the density decreases- Why?The exception: solid water is less dense then liquid water- Why?
7 Ideas from lab 17.2Layering is a qualitative method of comparing densities of different fluidsThe most dense fluid will be at the bottom, the least dense fluid will be at the top.Some real-life uses for layering: oil refineries, steel blast furnance
8 Buoyancy The measure of the upward force a fluid exerts on an object Archimedes principle- the force exerted on the object is = to the weight of fluid displaced by the object
9 Getting objects to float- Points from lab 17.3 To get an object to float, you need buoyant force to equal the force of the objectIn other words, the weight of the displaced water needs to equal the weight of the objectHow could you increase the amount of displaced water?Change the shape of the substance so the surface area is increased and will displace more waterThis also changes its density by increasing the object’s volume while the mass remains unchanged.
10 Viscosity Definition: material’s resistance to flow What determines viscosity? The ease at which molecules can move past one anotherThis depends on:the size and shape of the moleculehow tightly packed the molecules are
11 Temperature and viscosity As temp increases liquids usually become less viscous because molecules are spread out more and molecules have an easier time moving past one anotherGases become MORE viscous with increasing temperature- this is because as molecules move around more, they will collide more creating more friction and greater resistance to flow
12 Compressibility of gases Since molecules in a gas are far apart, they can be compressed to decrease its volume.Adding pressure will compress gases, leaving empty space were the gas molecules used to occupyOnce the pressure is released, then the gas will expand, filling the empty space
13 Cartesian diversIf pressure is applied to the system, the gas inside the diver compressesThis compression allows space for water to enterThis added water increases the density, then the diver sinksWhat causes it to float again?