Questions ofQuestions ofHeat Energy, Matter and Heat Energy, Matter and

DensityDensity

The ThermometerThe Thermometer

The ThermometerThe Thermometer

Mr. Martinez placed a thermometer in a jar Mr. Martinez placed a thermometer in a jar of very hot water. His students watched of very hot water. His students watched what happened to the thermometer. what happened to the thermometer. Immediately the level of the red liquid in Immediately the level of the red liquid in the thermometer went up. His students the thermometer went up. His students disagreed about why the red liquid in the disagreed about why the red liquid in the thermometer rose when the thermometer thermometer rose when the thermometer was placed in the hot water. This is what was placed in the hot water. This is what they said:they said:

Jean-Paul: “The hot water pushed it up”Jean-Paul: “The hot water pushed it up”

Pita: “The mass of the red liquid increased”Pita: “The mass of the red liquid increased”

Jonathan: “The heat inside the thermometer Jonathan: “The heat inside the thermometer pulls it up”pulls it up”

Jimena: “The air inside the thermometer pulls it Jimena: “The air inside the thermometer pulls it up”up”

Molly: “The molecules of the red liquid are Molly: “The molecules of the red liquid are further apart”further apart”

Greta: “The number of molecules of the red Greta: “The number of molecules of the red liquid increased”liquid increased”

Keanu: “The molecules of the red liquid are Keanu: “The molecules of the red liquid are getting bigger”getting bigger”

Who is correct?Who is correct?

Molly. The thermometer is a closed system. Molly. The thermometer is a closed system. It operates on the principle that the fluid It operates on the principle that the fluid inside (usually alcohol) expands when inside (usually alcohol) expands when heated and contracts when cooled. When heated and contracts when cooled. When the fluid is in contact with the warm water, the fluid is in contact with the warm water, energy from the hot water is transferred to energy from the hot water is transferred to the liquid inside the thermometer. The the liquid inside the thermometer. The molecules of liquid inside the thermometer molecules of liquid inside the thermometer gain energy, start moving faster, bumping gain energy, start moving faster, bumping into each other, and move further apart using into each other, and move further apart using more space.more space.

Comparing CubesComparing CubesComparing CubesComparing Cubes

Sophia has two solid cubes made of the Sophia has two solid cubes made of the same material. One cube is very large, same material. One cube is very large, and the other cube is very small. and the other cube is very small. Density equals mass divided by volume: d=m/vDensity equals mass divided by volume: d=m/v

a)a) The density of the larger cube is greater The density of the larger cube is greater than that of the smaller cubethan that of the smaller cube

b)b) The density of the smaller cube is greater The density of the smaller cube is greater than that of the larger cubethan that of the larger cube

c)c) The density of both cubes are the sameThe density of both cubes are the same

Cubes ExplainedCubes Explained

The reason why the large and small cubes The reason why the large and small cubes have the same density is because they are have the same density is because they are made from the same material, and the made from the same material, and the molecules are arranged in the same exact molecules are arranged in the same exact way for both cubes.way for both cubes.

This is similar to the reason why water’s This is similar to the reason why water’s density is always 1 g/ml, regardless of how density is always 1 g/ml, regardless of how much or how little water you have!much or how little water you have!

Floating LogsFloating Logs

A log was cut from a tree and put in the A log was cut from a tree and put in the water. The log floated on its side so that water. The log floated on its side so that half the log was above the water surface. half the log was above the water surface. Another log was cut from the same tree. Another log was cut from the same tree. This log was twice as long and twice as This log was twice as long and twice as wide. How does the larger log float wide. How does the larger log float compared with the smaller log?compared with the smaller log?

a)a) More than half of the larger log floats above More than half of the larger log floats above the water surface.the water surface.

b)b) Half of the larger log floats above the water Half of the larger log floats above the water surface.surface.

c)c) Less than half of the larger log floats above Less than half of the larger log floats above the water surface.the water surface.

Floating LogsFloating Logs

b) Half of the larger log floats above the b) Half of the larger log floats above the surface. Density is a property of matter surface. Density is a property of matter that does not depend on the amount of that does not depend on the amount of material. If one sample is very large and material. If one sample is very large and the other is very small, the mass to volume the other is very small, the mass to volume ratio is still the same, and the molecules ratio is still the same, and the molecules are still arranged in the same way, so the are still arranged in the same way, so the density remains the same.density remains the same.

Floating High & LowFloating High & LowSam floated in a pool of water. He floated Sam floated in a pool of water. He floated half way above and half way below the half way above and half way below the water level. What can Sam do to make water level. What can Sam do to make himself float like Daffy Duck, who is floating himself float like Daffy Duck, who is floating just beneath the water surface?just beneath the water surface?

Floating High & LowFloating High & Lowa)a) Sam needs to have less density than DaffySam needs to have less density than Daffyb)b) Sam needs to have more density than DaffySam needs to have more density than Daffyc)c) Sam could add weights (more mass) on his Sam could add weights (more mass) on his

stomachstomachd)d) Sam could add weights on Daffy’s stomachSam could add weights on Daffy’s stomache)e) Add more water to the pool so it is deeperAdd more water to the pool so it is deeperf)f) Add salt to the waterAdd salt to the water

– Answers: b and cAnswers: b and c

To make Sam float so that more of him is under the To make Sam float so that more of him is under the water, you must increase his density, which can be water, you must increase his density, which can be done by adding heavy weights to his body. Adding done by adding heavy weights to his body. Adding more water affects both Sam & Daffy, as does more water affects both Sam & Daffy, as does adding salt (increasing water’s density)adding salt (increasing water’s density)

Ice Cubes in a BagIce Cubes in a Bag

You have ice cubes in a sealed bag and You have ice cubes in a sealed bag and record the mass. Ten minutes later, after record the mass. Ten minutes later, after the cubes have melted, you check the the cubes have melted, you check the mass again.mass again.

a)a) The mass of the water in the bag will be The mass of the water in the bag will be lessless than the mass of the ice in the bagthan the mass of the ice in the bag

b)b) The mass of the water in the bag will be The mass of the water in the bag will be moremore than the mass of the ice in the bagthan the mass of the ice in the bag

c)c) The mass of the water in the bag will be the The mass of the water in the bag will be the samesame as the mass of the ice cubes in the bag as the mass of the ice cubes in the bag

Ice Cubes In A BagIce Cubes In A Bag

C). The mass of the C). The mass of the water in the bag will water in the bag will be the same as the be the same as the mass of the ice mass of the ice cubes in the bag, cubes in the bag, as long as none of as long as none of the Hthe H22O molecules O molecules were allowed to were allowed to escape the bagescape the bag

LemonadeLemonadeA glass of lemonade had a mass of 255 g. A A glass of lemonade had a mass of 255 g. A spoonful of sugar with a mass of 25 g is stirred spoonful of sugar with a mass of 25 g is stirred into the lemonade. Predict the mass of the into the lemonade. Predict the mass of the lemonade with the sugar added.lemonade with the sugar added.

a)a) It will have a mass of slightly less than 255 It will have a mass of slightly less than 255 grams but more than 230 gramsgrams but more than 230 grams

b)b) Its mass will be slightly more than 255 grams Its mass will be slightly more than 255 grams but less than 280 gramsbut less than 280 grams

c)c) Its mass will be 230 gramsIts mass will be 230 gramsd)d) Its mass will be 280 gramsIts mass will be 280 gramse)e) Its mass will be 255 gramsIts mass will be 255 grams

LemonadeLemonade

D) Its mass will be D) Its mass will be 280g, but its 280g, but its volumevolume will remain will remain unchanged. unchanged. Therefore, the Therefore, the lemonade lemonade becomes more becomes more dense with more dense with more sugar!sugar!

Rusty NailsRusty NailsYou have four dry iron nails and record the You have four dry iron nails and record the mass. You then put the nails in a moist, open mass. You then put the nails in a moist, open dish and exposed to the air over several dish and exposed to the air over several weeks. Will the mass of the rusted nails be weeks. Will the mass of the rusted nails be different than the dry, unrusted nails?different than the dry, unrusted nails?

a)a) The mass of the dry rusted nails will be The mass of the dry rusted nails will be moremore than the mass of the dry nails before they are than the mass of the dry nails before they are rustedrusted

b)b) The mass of the dry rusted nails will be The mass of the dry rusted nails will be lessless than than the mass of the dry nails before they rustedthe mass of the dry nails before they rusted

c)c) The mass of the dry rusted nails will be the The mass of the dry rusted nails will be the samesame as the mass of the dry nails before they rustedas the mass of the dry nails before they rusted

Rusty NailsRusty NailsA) The mass of the dry A) The mass of the dry rusted nails will be more rusted nails will be more than the mass of the dry than the mass of the dry nails before they are nails before they are rusted. This is due to rusted. This is due to the fact that rust is the the fact that rust is the product of iron product of iron chemically reacting and chemically reacting and combining with oxygen combining with oxygen in the air. More in the air. More molecules = more mass.molecules = more mass.

Cookie CrumblesCookie CrumblesYou have a whole cookie that you You have a whole cookie that you aggressively crush into tiny pieces and aggressively crush into tiny pieces and crumbs. You measure the mass of all the crumbs. You measure the mass of all the pieces and crumbs.pieces and crumbs.

a)a) The The whole cookie’s mass is greater whole cookie’s mass is greater than all than all of the cookie crumbsof the cookie crumbs

b)b) All of the All of the cookie crumbs have more masscookie crumbs have more mass than the whole cookiethan the whole cookie

c)c) The whole cookie and all of the cookie The whole cookie and all of the cookie crumbs crumbs have equal masshave equal mass

Cookie CrumblesCookie Crumbles

c) The whole c) The whole cookie and all of cookie and all of the cookie crumbs the cookie crumbs have the same have the same mass, because no mass, because no molecules are molecules are gained or lost in gained or lost in the crushing.the crushing.

What’s in the Bubbles?What’s in the Bubbles?

Hannah is boiling water in a glass tea kettle. She Hannah is boiling water in a glass tea kettle. She notices bubbles forming on the bottom of the notices bubbles forming on the bottom of the kettle that rise to the top and wonders what is in kettle that rise to the top and wonders what is in the bubbles. She asks her family and this is what the bubbles. She asks her family and this is what they say:they say:

a)a) Dad: “They are bubbles of heat”Dad: “They are bubbles of heat”b)b) Calvin: “The bubbles are filled with air”Calvin: “The bubbles are filled with air”c)c) Grandma: “The bubbles are an invisible form Grandma: “The bubbles are an invisible form

of water”of water”d)d) Mom: “The bubbles are empty, nothing inside Mom: “The bubbles are empty, nothing inside

them”them”e)e) Lucy: “The bubbles contain oxygen and Lucy: “The bubbles contain oxygen and

hydrogen that separated from the water”hydrogen that separated from the water”

What’s in the Bubbles?What’s in the Bubbles?– Dad: “They are bubbles of heat”Dad: “They are bubbles of heat”– Calvin: “The bubbles are filled with air”Calvin: “The bubbles are filled with air”– Grandma: “The bubbles are an invisible form Grandma: “The bubbles are an invisible form

of water”of water”– Mom: “The bubbles are empty, nothing inside Mom: “The bubbles are empty, nothing inside

them”them”– Lucy: “The bubbles contain oxygen and Lucy: “The bubbles contain oxygen and

hydrogen that separated from the water”hydrogen that separated from the water”

Grandma is correct! This invisible water is called water Grandma is correct! This invisible water is called water vapor. When heat energy is applied, it results in vapor. When heat energy is applied, it results in increased molecular movement. The heated molecules increased molecular movement. The heated molecules can no longer remain in the liquid state and they can no longer remain in the liquid state and they become gaseous water vapor. (Water vapor is unlike become gaseous water vapor. (Water vapor is unlike steam which contains some condensed liquid water.)steam which contains some condensed liquid water.)

Ice Cold LemonadeIce Cold Lemonade

It was a hot summer day. Mattie poured herself It was a hot summer day. Mattie poured herself a glass of lemonade. The lemonade was warm, a glass of lemonade. The lemonade was warm, so Mattie put some ice in the glass. After 10 so Mattie put some ice in the glass. After 10 minutes, Mattie noticed that the ice was melting minutes, Mattie noticed that the ice was melting and the lemonade was cold. Mattie wondered and the lemonade was cold. Mattie wondered what made the lemonade get cold. She had what made the lemonade get cold. She had three different ideas. Which idea do you think three different ideas. Which idea do you think best explains why the lemonade got cold?best explains why the lemonade got cold?

Ice Cold LemonadeIce Cold Lemonade

a)a) The coldness from the ice moved into the The coldness from the ice moved into the lemonadelemonade

b)b) The heat from the lemonade moved into the The heat from the lemonade moved into the iceice

c)c) The coldness and the heat moved back and The coldness and the heat moved back and forth until the lemonade cooled offforth until the lemonade cooled off

Remember how heat flows….Remember how heat flows….

The heat from the lemonade moved into The heat from the lemonade moved into the ice. the ice. Heat energy will only move from a Heat energy will only move from a warmer object to a cooler object, never the warmer object to a cooler object, never the other way aroundother way around. The warm molecules of . The warm molecules of the lemonade came into contact with the the lemonade came into contact with the cooler molecules of the ice. Heat energy cooler molecules of the ice. Heat energy flowed INTO the ice FROM the lemonade. flowed INTO the ice FROM the lemonade. This resulted in a the melting of the ice, This resulted in a the melting of the ice, which cooled the lemonade.which cooled the lemonade.

Mixing WaterMixing WaterMelinda filled two glasses of equal size half-full Melinda filled two glasses of equal size half-full with water. The water in one glass was 50 with water. The water in one glass was 50 degrees Celsius. The water in the other glass degrees Celsius. The water in the other glass was 10 degrees Celsius. She poured one glass was 10 degrees Celsius. She poured one glass into the other, stirred the liquid, and measured into the other, stirred the liquid, and measured the temperature of the full glass of water.the temperature of the full glass of water.What do you think the temperature of the full What do you think the temperature of the full glass of water will be after the water is mixed?glass of water will be after the water is mixed?

a)a) 20 degrees Celsius20 degrees Celsiusb)b) 30 degrees Celsius30 degrees Celsiusc)c) 40 degrees Celsius40 degrees Celsiusd)d) 50 degrees Celsius50 degrees Celsiuse)e) 60 degrees Celsius60 degrees Celsius

Mixing WaterMixing Watera)a) 20 degrees Celsius20 degrees Celsius

b)b) 30 degrees Celsius30 degrees Celsius

c)c) 40 degrees Celsius40 degrees Celsius

d)d) 50 degrees Celsius50 degrees Celsius

e)e) 60 degrees Celsius60 degrees Celsius

Temperature is a measure of the average Temperature is a measure of the average motion of the particles that make up the motion of the particles that make up the water. When the cooler water and the water. When the cooler water and the warmer water are mixed together, a warmer water are mixed together, a transfer of energy occurs.transfer of energy occurs.

Mixing WaterMixing WaterThe flow of heat moves from the molecules of The flow of heat moves from the molecules of

the warmer water to the molecules in the the warmer water to the molecules in the cooler water until they have the same cooler water until they have the same average energy (temperature). average energy (temperature).

Since the two samples of water were identical Since the two samples of water were identical in volume, the thermal equilibrium that is in volume, the thermal equilibrium that is reached is an average of the two reached is an average of the two temperatures, 30 degrees Celcius.temperatures, 30 degrees Celcius.