Chapter 17.2 and 17.3Notes

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’ Principle

In 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

Archimedes’ Principlein action:

What is Buoyancy?

*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 gas increases, its volume decreases; as the pressure of a gas decreases, its volume increases.

Charles Law & Boyle’s Law

*Properties of Liquids• *Viscosity is the measure of a material’s resistance to flow.– High Viscosity= high resistance to flow

Ketchup, yogurt, honey– Low Viscosity= low resistance to flow

oil, water, juice

Low

High

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)

Examples of Viscosity:

Summarize: Explain in your own words:

• Explain these ideas and give examples of each:

1.Archimedes’ Principle.

2.Boyle’s Law.

3.Charles’ Law.