Chapter 17.2 and 17.3 Notes Mrs. Neistadt Physical Science
Chapter 17.2 Notes• DQ: Concept Review Question #4: Would a cube of solid silver sink or float in liquid silver? How do you know? (pg 301) – Solid silver is more dense than liquid silver. A solid silver rock would sink if dropped into a liquid pool of silver.• Liquids tend to be less dense than when in their solid form.
17.2 Density of Fluids• The mass is the same- but in liquids, the atoms are able to spread out, which makes their volume bigger.• The atoms are spread out causing most liquids to be less dense than solids.
17.2 Density of Water• *Water is an exception. – *Ice is less dense than liquid water, so ice floats. – Water molecules are more tightly packed when in liquid form.
17.3 Buoyancy of Fluids Notes• *What is buoyancy?• *Buoyancy- is the measure of upward force a fluid exerts on an object.
Archimedes’ PrincipleIn third Century BC, a Greek Mathematician named Archimedes discovered:• *The force exerted on an object in liquid is equal to the weight of the fluid displaced by the object.• *This relationship is called Archimedes’ Principle
*Buoyancy and Gases• *In 1787 Jacques Charles discovered a principle that describes the forces that allow gases to float.• This force explains why balloons filled with helium or hot air will float.
Buoyancy and Gases• *Charles’ Law- The volume of gas increases with increasing temperature; the volume of gas decreases with decreasing temperature
Examples of Charles’ Law:• Soccer ball left outside on cold night• Bicycle/Car tires in the winter• Party balloons left in a hot car
Boyle’s Law• A law explaining the relationship between gas, pressure and volume is Boyle’s Law.• You see Boyle’s Law in action when you observe gases under high pressure: – Fire extinguishers – Spray cans – Even volcanoes!
Boyle’s Law*Boyle’s Law- as the pressure of a gasincreases, its volume decreases; as thepressure of a gas decreases, its volumeincreases.
*Properties of Liquids• *Viscosity is the measure of a material’s resistance to flow. H – High Viscosity= high resistance to flow i Ketchup, yogurt, honey g – Low Viscosity= low resistance to flow h oil, water, juice Low
Why are some liquids more viscous?• *The shape of the molecules in the liquid determine the viscosity.• Bigger, bumpier molecules = more viscosity• *The temperature of the liquid also determines viscosity.• Higher temperature = less viscosity (pours quickly)• Lower temperature = more viscosity (pours slowly)