Chapter 17 Notes

Overview of Chapter 17

Properties of Matter

SolidsFluids

(liquids and gases)

DensityOthers

(brittleness, tensileStrength, etc)

Density Buoyancy ViscosityCompression

(gases)

Properties of Solids Density- describes the relationship b/t mass and

volume of homogenous material- tells how tightly molecules are “packed”

Formula: D=m/v What are the units of density? Density stays the same no matter how large or

small the sample is Heterogenous materials may not have the same

density throughout

Ideas from lab 17.1 Density does not depend on size of the

material Density does depend on the type of

material Density does not depend on the shape of

the material (unless you have altered volume)

Density does depend on the state of matter

Other properties Hardness-resistance to scratching Elasticity-ability to stretch then return to original

shape Brittleness-tendency to shatter on impact Malleability- ability to be pounded into sheets Tensile strength- measures how much tension a

material can withstand without breaking

Density of Fluids Fluid- 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?

Ideas from lab 17.2 Layering is a qualitative method of

comparing densities of different fluids The 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

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

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 object In other words, the weight of the displaced water

needs to equal the weight of the object How could you increase the amount of displaced

water? Change the shape of the substance so the surface area

is increased and will displace more water This also changes its density by increasing the object’s

volume while the mass remains unchanged.

Viscosity Definition: material’s resistance to flow What determines viscosity? The ease at

which molecules can move past one another This depends on:

the size and shape of the molecule how tightly packed the molecules are

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 another

Gases 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

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 occupy Once the pressure is released, then the gas will

expand, filling the empty space

Cartesian divers If pressure is applied to the system, the gas

inside the diver compresses This compression allows space for water to

enter This added water increases the density, then

the diver sinks What causes it to float again?