1. Those electrons most important in determining the behavior of an element are:

A. core electrons, found in the inside energy levels.

B. valence electrons found in the outside energy level or valence shell.

C. all of the electrons each atom of an element has.

D. None of them, neutrons are most important.

2. The elements in Group 18 of the periodic table which usually do not join in chemical bonds are called:

A. noble gases.

B. metalliods.

C. metals.

D. alkali earth metals.

3. Which of the following equations correctly shows the conservation of mass?

A. HgO---> Hg + O2.

B. BaSO4 + C ---> BaS + CO .

C.H2SO4 + 2KOH---->K2SO4 + 2H2O.

D. NiCl2 + 2NaOH---->Ni(OH)2 + NaCl.

4. Which of the following is a chemical change?

A. dissolving sodium hydroxide into water.

B. sublimation of dry ice into carbon dioxide gas.

C. combustion of hydrogen gas with oxygen gas to make water.

D. fractional distillation of crude oil .

Matter

Density

One characteristic of matter is DENSITY

Density = mass / volume

Unit: kg / m3 or g / cm3

The density of water is 1000 kg / m3

Or 1 g / cm3

An object will float in a liquid if its density is less than that of the liquid.

5. A block of maple wood with a volume of 405 cubic centimeters and a density of 0.67 g/ cm3 is sawed in half. The density of the two smaller blocks is now —

A one-fourth the original density

B one-half the original density

C two times the original density

D the same as the original density

6. This pipette is filled with a 20% NaOH solution. The solution is at 20°C and has a density of 1.23 g/mL. According to this information, what is the mass of this NaOH solution?

A 3.88 g B 15.7 g C 23.9 g D 24.6 g

Solids

Crystal Structure: atoms arranged in regular patterns. Example: salt, metal

Amorphous: atoms have no regular arrangement. Example: wax

Compression: occurs when parts are pressed together

Tension: when parts are pulled away from each other

Solids, liquids, and gases can all exert pressure.

Pressure =

SI unit for Pressure : = one Pascal, Pa

One Pascal of pressure is very small. It is the same as

1 Newton of Force (about ¼ pound) spread out over 1 square meter.

Pressure

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areaForce

If a solid is resting on top of a surface, the force it exerts is its weight.

Only the area actually in contact with the surface is used.

The same amount of force spread out over a smaller area results in more pressure.

Example: The pressure on the floor when someone is wearing tennis shoes compared to high heels.

The Force pushing down is the same in both cases

Force = the weight of the person,

But the area is much smaller for high heels, therefore the pressure is much higher.

Our atmosphere is a gas that exerts pressure. The further you go from Earth’s surface, the less air and the less air pressure there is. The air pressure at sea level is called “one atmosphere” and is equal to

One atmosphere, 1 atm = 100,000 Pa= 14.7 pounds per square inch (psi) !!In addition to measuring pressure in

Pascals, sometimes pressure is measured in atm or psi or mm Hg or torr.

Our atmosphere is a gas that exerts pressure. The further you go from Earth’s surface, the less air and the less air pressure there is. The air pressure at sea level is called “one atmosphere” and is equal to

One atmosphere, 1 atm = 100,000 Pa= 14.7 pounds per square inch (psi) !!In addition to measuring pressure in

Pascals, sometimes pressure is measured in atm or psi or mm Hg or torr.

Barometer

A barometer measures atmospheric pressure by pushing up a column of fluid.

Normal atmospheric pressure can push a column of water up 10.3 meters and a column of mercury up 76 cm.

Without an atmosphere, a straw won’t work! There’s nothing to push the fluid up the straw.

Water Barometer

Pressure at different depths in a fluid

The deeper you go in a fluid, the greater the pressure.

Pressure = density x gravity x height

P = D g h

Pressure = Dgh

The pressure in a fluid does NOT depend on the shape of the container or the Volume of the fluid.

Where is the pressure the greatest?

At the bottom of a 2 m long test tube OR at the bottom of a 2 m deep swimming pool?

IT’S THE SAME!!

7. A scuba diver experiences an increasing pressure as he dives beneath the surface of a deep lake. What is the pressure in Pascals two meters below the surface of water? Use g = 10m/s2.

Use the formula!! P = Dgh

• Gauge pressure is the pressure reading on a gauge and does not include atmospheric pressure.

• Absolute pressure requires that the atmospheric pressure also be included.

Pascal's principle

Pascal's principle :

Pressure applied to an enclosed fluid is transmitted undiminished to every part of the

fluid.

Pascal's principle can be used to explain how hydraulic systems work. A common example of such a system is the lift used to raise a car off the ground so it can be repaired at a garage.

HydraulicsIn a hydraulic lift, a small force

applied to a small-area piston is transformed to a large force at a large-area piston. If a car sits on top of the large piston, it can be lifted by applying a relatively small force.

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Area

Area

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P P

Force Force

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Even though the forces are different, the work done is the same.

Work is force times the distance, so if the force on the large piston is 10 times larger than the force on the smaller piston, the distance it travels is 10 times smaller.

Work is ENERGY, which can’t be created or destoyed. So you just CAN’T get more energy out than you put in!!!

ExampleA mechanic uses a hydraulic

jack to lift cars. He can easily exert a force of 30 N. On the jack, the area of the small piston is 0.0026 m2. The area of the larger piston is 3.6 m2.

What is the heaviest car he can lift?

The weight of the car is the LARGE FORCE.

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Forcelarge = (3.6 / .0026) x 30 =

41,538 N

1. The head of a giraffe is 2.0 m above its heart and the density of the blood is 1.05 x 103 kg / m3. What is the difference in the pressure between the giraffe’s heart and head?

2. How much pressure is needed in ground-based pipes to pump water up to the top floor of a building 410 m above the ground?

3. What is the gauge pressure 3 meters down in a swimming pool? What is the absolute pressure (including atmospheric pressure)?

4. The density of ocean water is about 1027 kg/m3. At what depth is the pressure 92,000 Pa?

5. To lift a 14000 N car with a hydraulic lift, the mechanic exerts a force of 50 N on the input piston, which has an area of 8 cm2. What is the area of the output piston?

6. A mechanic is raising a 12000 N car on a hydraulic lift. The area of the input piston is 12 cm2 and the output piston is 700 cm2. What force must be exerted?

7. The Flying Umbrella ride at the Amusement Park is lifted by a hydraulic jack. The operator applies a 72 N force to a piston of area 0.003 m2, which holds the 20,000 N ride off the ground. What is the area of the larger piston?

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How much of a object will be submerged in a fluid?

% submerged = Density of object / density of fluid

For example, what percentage of an ice berg is submerged? Density of ice = 917 kg/m3Density of sea water = 1025 kg/m3Answer: 89.4%

Archimedes Principle

An object immersed in a fluid is buoyed up with a force that is equal to the weight of the displaced fluid.

That’s why you seem to weigh less in a swimming pool that you actually do!

Pure gold, because of its high density, would displace LESS water than a crown made with a little gold mixed with cheaper metals.

Apparent Weight = Actual Weight – Buoyant Force

Buoyant Force = Weight of displaced fluid

But buoyancy also applies to air. It is what gives a lifting force to hot air balloons.

Archimedes' Principle explains why steel ships float

Which of the following statements explain why a steel ship will float on water but a bar of steel will sink:

A. Because of the air in the ship’s hull, the overall density of the ship is less than the density of water.

B. The buoyant force on the ship is greater than the weight of the ship.

C. The densest part of the ship is the part that is out of the water.

D.When rolled into a sheet, steel is less dense than water.

The Titanic, April 15, 1912

The hull was designed to displace 66,000 tons of water.

The gross weight was 46,328 tons.

Therefore, the Titanic had 19,672 tons of extra displacement capacity.

19672 Tons to spareThe Titanic had 16 compartments separated

by 15 watertight bulkheads. If each compartment had the same displacement capacity, then each one would have 4125 tons (66000 / 16).

One flooded compartment: 19,672 – 4125The Titanic is able to stay afloat.Two compartments:Three compartments:Four compartments:Five compartments:

Damage to the hull amounted to only

12 square feet, but punctured 5 compartments.

The sinking was inevitable.

Fluids in Motion

Fluids include both liquids and gases.

Viscosity: the resistance to flow

Honey is more viscous than water.

Bernoulli’s Principle

The faster a fluid is moving, the lower the pressure within the fluid.

FASTER fluid results in LOWER pressure

SLOWER fluid results in HIGHER pressure

There are MANY applications of Bernoulli’s Principle.

Air Foil

The shape of an airplane wing.

The air moving over the top of the wing reaches the back of the wing at the same time as the air moving along the bottom of the wing. This implies that…..

Air moves faster over the top of the wing. According to Bernoulli’s principle, that results in lower air pressure above the wings than below the wings.

The higher pressure below helps push the wings upward.That’s “lift”.

Atomizer or Paint SprayerA small tube goes down into the

liquid in the container.

Fast moving air moves over the top of the small tube, According the Bernoulli’s principle, this results in LOWER pressure at the top of the tube.

So… the higher pressure at the bottom of the tube will push the fluid up the tube.

Chimney’s

The wind blowing over the top of a chimney results in a LOWER air pressure at the top of the chimney compared to the bottom of the chimney.

The higher pressure air at the bottom helps push the smoke up and out the chimney.

Animal BurrowsThere are TWO opening to a

burrow, one at a higher elevation than the other.

More wind blows over the higher opening, which results in LOWER air pressure over that opening than the other opening

The higher pressure from the second opening pushes the air through the burrow creating a constant airflow.

AneurysmA serious medical condition that can result in death if

not treated promptly.A weakened section of a blood vessel begins to swell

outwards – the vessel widens.This forms an area where the blood slows down:

SLOWER fluid results in HIGHER pressure.This higher pressure makes the vessel swell out even

more…Which makes the pressure go higher…Which makes the vessel swell more…Which…… you get the idea!If not corrected, the vessel will eventually burst. If it is

a major vessel, this a critical situation!

Blaise Pascal 1623-1662

At the age of 18, Pascal began designing a calculating machine, which he finally perfected when he was thirty, the pascaline, a beautiful handcrafted box about fourteen by five by three inches. The first accurate mechanical calculator was born. The Pascaline was not a commercial success in Pascal's lifetime; it could do the work of six accountants and people feared it would create unemployment.

The computer programming language, PASCAL is named for him as well as the unit for pressure.