13.1 Degrees

Which is the largest unit: one Celsius degree, one Kelvin degree, or one Fahrenheit degree?

1) one Celsius degree2) one Kelvin degree3) one Fahrenheit degree4) both one Celsius degree and one Kelvin degree5) both one Fahrenheit degree and one Celsius degree

13.113.1 DegreesDegrees

Which is the largest unit: one Celsius degree, one Kelvin degree, or one Fahrenheit degree?

1) one Celsius degree2) one Kelvin degree3) one Fahrenheit degree4) both one Celsius degree and one Kelvin degree5) both one Fahrenheit degree and one Celsius degree

The Celsius degree and the Kelvin degree are the same size. The scales only differ by an offset, not by the size of the degree unit. For Fahrenheit, there are 180 degrees between boiling and freezing (212°F–32°F). For Celsius, there are 100 degrees between the same points, so the Celsius (and Kelvin) degrees must be larger.

13.113.1 DegreesDegrees

It turns out that – 40°C is the same temperature as – 40°F. Is there a temperature at which the Kelvin and Celsius scales agree?

1) yes, at 0 °C 2) yes, at -273 °C3) yes, at 0 K4) no

13.213.2 Freezing ColdFreezing Cold

It turns out that – 40°C is the same temperature as – 40°F. Is there a temperature at which the Kelvin and Celsius scales agree?

1) yes, at 0 °C 2) yes, at -273 °C3) yes, at 0 K4) no

The Celsius and Kelvin scales differ only by an offset, which is 273 degrees. Therefore, a temperature on one scale can never match the same numerical value on the other scale. The reason that such agreement is possible for Celsius and Fahrenheit is the fact that the actual degree units have different sizes (recall the previous question).

13.213.2 Freezing ColdFreezing Cold

13.413.4 GlassesGlasses

1) run hot water over them both

2) put hot water in the inner one

3) run hot water over the outer one

4) run cold water over them both

5) break the glasses

Two drinking glasses are stuck, one inside the other. How would you get them unstuck?

Running hot water only over the outer glassouter glass will allow the outer one to expandouter one to expand, while the inner glass remains relatively unchanged. This should loosen the outer glass and free it.

13.413.4 GlassesGlasses

1) run hot water over them both

2) put hot water in the inner one

3) run hot water over the outer one

4) run cold water over them both

5) break the glasses

Two drinking glasses are stuck, one inside the other. How would you get them unstuck?

A steel tape measure is marked such that it gives accurate length measurements at room temperature. If the tape measure is used outside on a very hot day, how will its length measurements be affected?

1) measured lengths will be too small2) measured lengths will still be accurate3) measured lengths will be too big

13.5a13.5a Steel Expansion ISteel Expansion I

A steel tape measure is marked such that it gives accurate length measurements at room temperature. If the tape measure is used outside on a very hot day, how will its length measurements be affected?

1) measured lengths will be too small2) measured lengths will still be accurate3) measured lengths will be too big

The tape measure will expand, so its markings will spread out farther than the correct amount. When it is laid down next to an object of fixed length, you will read too few markings for that given length, so the measured length will be too small.

13.5a13.5a Steel Expansion ISteel Expansion I

1) gets larger

2) gets smaller

3) stays the same

4) vanishes

Metals such as brass expand when heated. The thin brass plate in the movie has a circular hole in its center. When the plate is heated, what will happen to the hole?

13.5b13.5b Steel Expansion IISteel Expansion II

1) gets larger

2) gets smaller

3) stays the same

4) vanishes

Imagine drawing a circle on the plate. This circle will expand This circle will expand outward along with the rest of the outward along with the rest of the plate.plate. Now replace the circle with the hole, and you can see that the hole will expand outward as well. Note that the material does Note that the material does NOTNOT “expand inward” to fill the hole!!“expand inward” to fill the hole!!

expansionexpansion

Metals such as brass expand when heated. The thin brass plate in the movie has a circular hole in its center. When the plate is heated, what will happen to the hole?

13.5b13.5b Steel Expansion IISteel Expansion II

Two objects are made of the same material, but have different masses and temperatures. If the objects are brought into thermal contact, which one will have the greater temperature change?

1) the one with the higher initial temperature2) the one with the lower initial temperature3) the one with the greater mass4) the one with the smaller mass5) the one with the higher specific heat

14.1a14.1a Thermal Contact I Thermal Contact I

Two objects are made of the same material, but have different masses and temperatures. If the objects are brought into thermal contact, which one will have the greater temperature change?

1) the one with the higher initial temperature2) the one with the lower initial temperature3) the one with the greater mass4) the one with the smaller mass5) the one with the higher specific heat

Since the objects are made of the same material, the only difference between them is their mass. Clearly, the object with less mass will be much easier to change temperature since there is not much material there (compared to the more massive object).

14.1a14.1a Thermal Contact I Thermal Contact I

14.214.2 Two Liquids Two Liquids

1) the cooler one

2) the hotter one

3) both the same

Two equal-mass liquids, initially at the same temperature, are heated for the same time over the same stove. You measure the temperatures and find that one liquid has a higher temperature than the other. Which liquid has a higher specific heat?

Both liquids had the same increase in internal energy,

because the same heat was added. But the cooler liquidcooler liquid

had a lower temperaturelower temperature change.

Since QQ = = mcmcTT, if QQ and mm are both the same and TT is

smaller, then cc (specific heat) must be bigger.

14.214.2 Two Liquids Two Liquids

1) the cooler one

2) the hotter one

3) both the same

Two equal-mass liquids, initially at the same temperature, are heated for the same time over the same stove. You measure the temperatures and find that one liquid has a higher temperature than the other. Which liquid has a higher specific heat?

The specific heat of concrete is greater than that of soil. A baseball field (with real soil) and the surrounding parking lot are warmed up during a sunny day. Which would you expect to cool off faster in the evening when the sun goes down?

1) the concrete parking lot2) the baseball field3) both cool off equally fast

14.3a14.3a Night on the Field Night on the Field

The specific heat of concrete is greater than that of soil. A baseball field (with real soil) and the surrounding parking lot are warmed up during a sunny day. Which would you expect to cool off faster in the evening when the sun goes down?

1) the concrete parking lot2) the baseball field3) both cool off equally fast

The baseball field, with the lower specific heat, will change temperature more readily, so it will cool off faster. The high specific heat of concrete allows it to “retain heat” better and so it will not cool off so quickly – it has a higher “thermal inertia.”

14.3a14.3a Night on the Field Night on the Field

14.414.4 Calorimetry Calorimetry

1 kg of water at 100 oC is poured into a

bucket that contains 4 kg of water at 0 oC. Find the equilibrium temperature

(neglect the influence of the bucket).

1) 0 oC

2) 20 oC

3) 50 oC

4) 80 oC

5) 100 oC

Since the cold water mass is greatercold water mass is greater, it will have a smaller temperature changesmaller temperature change!

The masses of cold/hot have a ratio of 4:1, so the temperature change must have a ratio of 1:4 (cold/hot).

14.414.4 Calorimetry Calorimetry

1 kg of water at 100 oC is poured into a

bucket that contains 4 kg of water at 0 oC. Find the equilibrium temperature

(neglect the influence of the bucket).

1) 0 oC

2) 20 oC

3) 50 oC

4) 80 oC

5) 100 oC

QQ11 = = QQ22

mm11ccTT11 = = mm22ccTT22

TT11 / / TT22 = = mm22 / / mm11

14.514.5 MoreMore CalorimetryCalorimetry

A 1 kg block of silver (c = 234 J/kg 0C ) is heated to 100 0C, then dunked in a tub of 1 kg of water (c = 4186 J/kg 0C ) at 0 0C. What is the final equilibrium temperature?

1) 0oC

2) between 0oC and 50oC

3) 50oC


5) 100oC

Since ccwaterwater >> >> ccsilversilver it takes more heat to more heat to

change the temperature of the water than it change the temperature of the water than it does to change the temperature of the silverdoes to change the temperature of the silver. In other words, it is much “harder” to heat the In other words, it is much “harder” to heat the water!!water!! Thus, the final temperature has to be closer to the initial temperature of the water.

14.514.5 MoreMore CalorimetryCalorimetry

A 1 kg block of silver (c = 234 J/kg 0C ) is heated to 100 0C, then dunked in a tub of 1 kg of water (c = 4186 J/kg 0C ) at 0 0C. What is the final equilibrium temperature?

1) 0oC


3) 50oC


5) 100oC

QQ11 = = QQ22

mcmc11TT11 = = mcmc22TT22

TT11 / / TT22 = = cc22 / / cc11

If you add some heat to a substance, is it possible for the temperature of the substance to remain unchanged?

1) yes2) no

14.614.6 Adding HeatAdding Heat

If you add some heat to a substance, is it possible for the temperature of the substance to remain unchanged?

1) yes2) no

Yes, it is indeed possible for the temperature to stay the same. This is precisely what occurs during a phase change – the added heat goes into changing the state of the substance (from solid to liquid or from liquid to gas) and does not go into changing the temperature! Once the phase change has been accomplished, then the temperature of the substance will rise with more added heat.

14.614.6 Adding HeatAdding Heat

Will potatoes cook faster if the water is boiling faster? 1) yes

2) no

14.714.7 Hot PotatoHot Potato

Will potatoes cook faster if the water is boiling faster? 1) yes

2) no

The water boils at 100 °C and remains at that temperature until all of the water has been changed into steam. Only then will the steam increase in temperature. Since the water stays at the same temperature, regardless of how fast it is boiling, the potatoes will not cook any faster.

14.714.7 Hot PotatoHot Potato

14.814.8 Water and Ice Water and Ice

You put 1 kg of ice at 0oC together with 1 kg of water at 50oC. What is the final temperature? LF = 80 cal/gcwater = 1 cal/g oC

1) 0oC


3) 50oC

4) greater than 50oC

How much heat is needed to melt the ice?QQ = = m Lm Lff = (1000= (1000gg) ) (80 cal/ (80 cal/gg) = 80,000 cal) = 80,000 cal

How much heat can the water deliver by cooling from 50oC to 0oC?QQ = = ccwaterwater mmTT = (1 cal/ = (1 cal/gg ooC) C) (1000 (1000gg) ) (50 (50ooC) = 50,000 calC) = 50,000 cal

Thus, there is not enough heat available to melt all the ice!!

14.814.8 Water and Ice Water and Ice

You put 1 kg of ice at 0oC together with 1 kg of water at 50oC. What is the final temperature? LF = 80 cal/gcwater = 1 cal/g oC

1) 0oC


3) 50oC


14.914.9 Ice and Steam Ice and Steam You put 1 kg of ice at 0oC together with 1 kg of steam at 100oC. What is the final temperature? LF = 80 cal/g, Lv = 540 cal/gcwater = 1 cal/g oC


2) 50oC


4) 100oC


How much heat is needed to melt the ice?Q Q = = m Lm Lff = (1000= (1000gg) ) (80 cal/ (80 cal/gg) = 80,000 cal) = 80,000 cal

How much heat is needed to raise the water temperature to 100oC?QQ = = ccwaterwater mmTT = (1 cal/ = (1 cal/gg ooC)C)(1000(1000gg))(100(100ooC) = 100,000 calC) = 100,000 cal

But if all of the steam turns into water, that would release 540,000 cal540,000 cal. Thus, some steam is left over, and the whole mixture stays at 100oC.

14.914.9 Ice and Steam Ice and Steam You put 1 kg of ice at 0oC together with 1 kg of steam at 100oC. What is the final temperature? LF = 80 cal/g, Lv = 540 cal/gcwater = 1 cal/g oC


2) 50oC


4) 100oC


14.1214.12 Heat Conduction Heat Conduction

Given your experience of what feels colder when you walk on it, which of the surfaces would have the highest thermal conductivity?

a) a rugb) a steel surfacec) a concrete floord) has nothing to do with

thermal conductivity

14.1214.12 Heat Conduction Heat Conduction

Given your experience of what feels colder when you walk on it, which of the surfaces would have the highest thermal conductivity?

a) a rugb) a steel surfacec) a concrete floord) has nothing to do with

thermal conductivity

All things being equal, bigger k leads to bigger heat loss.From the packet: Steel=50, Concrete=0.8,Human body=0.17, Wool=0.04, in units of W/m*C0).

Three ContainersThree Containers

1) container 1

2) container 2

3) container 3

4) all three are equal

Three containers are filled with water to the same Three containers are filled with water to the same height and have the same surface area at the height and have the same surface area at the base, but the total weight of water is different for base, but the total weight of water is different for each. Which container has the greatest total each. Which container has the greatest total force acting on its base?force acting on its base?

Three ContainersThree Containers

The pressure at the bottom of each container depends only on the height of water above it! This is the same for all the containers. The total force is the product of the pressure times the area of the base, but since the base is also the same for all containers, the total force is the same.

1) container 1

2) container 2

3) container 3

4) all three are equal

Three containers are filled with water to the same Three containers are filled with water to the same height and have the same surface area at the height and have the same surface area at the base, but the total weight of water is different for base, but the total weight of water is different for each. Which container has the greatest total each. Which container has the greatest total force acting on its base?force acting on its base?

When you drink liquid through a straw, which of the items listed below is primarily responsible for this to work?

1) water pressure2) gravity3) inertia4) atmospheric pressure5) mass

The Straw IThe Straw I

When you drink liquid through a straw, which of the items listed below is primarily responsible for this to work?

1) water pressure2) gravity3) inertia4) atmospheric pressure5) mass

When you suck on a straw, you expand your lungs, which reduces the air pressure inside your mouth to less than atmospheric pressure. Then the atmospheric pressure pushing on the liquid in the glass provides a net upward force on the liquid in the straw sufficient to push the liquid up the straw.

The Straw IThe Straw I

Wood in Water IWood in Water I

Two beakers are filled to the brim with water. A wooden

block is placed in the second beaker so it floats. (Some of

the water will overflow the beaker.) Both beakers are then

weighed. Which scale reads a larger weight?

same for both

The block in B displaces an amount of displaces an amount of

water equal to its weightwater equal to its weight, since it is floating. That means that the weight weight

of the overflowed water is equal to the of the overflowed water is equal to the

weight of the blockweight of the block, and so the beaker beaker

in B has the same weight as that in Ain B has the same weight as that in A.

Wood in Water IWood in Water I

Two beakers are filled to the brim with water. A wooden

block is placed in the second beaker so it floats. (Some of

the water will overflow the beaker.) Both beakers are then

weighed. Which scale reads a larger weight?

same for both

Two BricksTwo Bricks

1

2

1) greater

2) the same

3) smaller

Imagine holding two identical Imagine holding two identical bricks in place under water. bricks in place under water. Brick 1 is just beneath the Brick 1 is just beneath the surface of the water, while brick 2 surface of the water, while brick 2 is held about 2 feet down. The is held about 2 feet down. The force needed to hold brick 2 in force needed to hold brick 2 in place is:place is:

The force needed to hold the brick in The force needed to hold the brick in place underwater is: place underwater is: WW – – FFBB.. According

to Archimedes’ Principle, FB is equal to

the weight of the fluid displaced. Since Since each brick displaces the same amount of each brick displaces the same amount of fluid, then fluid, then FFBB is the same in both cases. is the same in both cases.

Two BricksTwo Bricks

1

2

1) greater

2) the same

3) smaller

Imagine holding two identical Imagine holding two identical bricks in place under water. bricks in place under water. Brick 1 is just beneath the Brick 1 is just beneath the surface of the water, while brick 2 surface of the water, while brick 2 is held about 2 feet down. The is held about 2 feet down. The force needed to hold brick 2 in force needed to hold brick 2 in place is:place is:

Archimedes IArchimedes I1) 1/4 2) 1/3 3) 4/3 4) 3/4 5) 2/1

An object floats in water with 3/4 of its volume submerged. What is the ratio of the density of the object to that of water?

Remember that we have:

so if the ratio of the volume of the volume of the displaced water to the volume of the displaced water to the volume of the object is 3/4object is 3/4, the object has 3/4 the 3/4 the density of waterdensity of water.

10.12a10.12a Archimedes IArchimedes I

fluid

object

object

fluid

VV

1) 1/4 2) 1/3 3) 4/3 4) 3/4 5) 2/1

An object floats in water with 3/4 of its volume submerged. What is the ratio of the density of the object to that of water?

10.12b10.12b Archimedes IIArchimedes II1) it floats just as before

2) it floats higher in the water

3) it floats lower in the water

4) it sinks to the bottom

The object is now placed in oil with a density half that of water.

What happens?

We know from before that the object has object has 3/4 the density of water3/4 the density of water. If the water is now replaced with oil, which has 1/2 the 1/2 the density of waterdensity of water, the density of the density of the object is larger than the density of the object is larger than the density of the oiloil. Therefore, it must sink to the bottom.

10.12b10.12b Archimedes IIArchimedes II1) it floats just as before

2) it floats higher in the water

3) it floats lower in the water

4) it sinks to the bottom

The object is now placed in oil with a density half that of water.

What happens?

10.15a10.15a Fluid Flow Fluid Flow

(1) one quarter(2) one half(3) the same(4) double

(5) four times

Water flows through a 1-cm diameter pipe connected to a 1/2-cm diameter pipe. Compared to the speed of the water in the 1-cm pipe, the speed in the 1/2-cm pipe is:

The area of the small pipe is less, so we know that the water will flow faster there. Since AA rr22, when the radius is reduced byradius is reduced by 1/21/2, the area is area is reduced by 1/4reduced by 1/4, so the speed must increase by 4 timesspeed must increase by 4 times to keep the flow rate ((AA vv)) constant.

10.15a10.15a Fluid Flow Fluid Flow

(1) one quarter(2) one half(3) the same(4) double

(5) four times

Water flows through a 1-cm diameter pipe connected to a 1/2-cm diameter pipe. Compared to the speed of the water in the 1-cm pipe, the speed in the 1/2-cm pipe is:

v1 v2

On Golden PondOn Golden Pond1) rises

2) drops

3) remains the same

4) depends on the size of the steel

A boat carrying a large chunk of A boat carrying a large chunk of steel is floating on a lake. The steel is floating on a lake. The chunk is then thrown overboard and chunk is then thrown overboard and sinks. What happens to the water sinks. What happens to the water level in the lake?level in the lake?

Initially the chunk of steel “floats” by sitting in the boat. The buoyant force is equal to the weightweight of the steel, and this will require a lot of displaced waterrequire a lot of displaced water to equal the weight of the steel. When thrown overboard, the steel sinks and only displaces its only displaces its volumevolume in water in water. This is not so much water -- certainly less than before -- and so the water level in the lake will drop.

On Golden PondOn Golden Pond1) rises

2) drops

3) remains the same

4) depends on the size of the steel

A boat carrying a large chunk of A boat carrying a large chunk of steel is floating on a lake. The steel is floating on a lake. The chunk is then thrown overboard and chunk is then thrown overboard and sinks. What happens to the water sinks. What happens to the water level in the lakelevel in the lake

13.1 Degrees

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