Temperature and Heat

Watch It SpreadOverview

For this introductory activity you will observe food coloring after it is placed into water of various temperatures.

Hypothesis: ? Materials:

food coloring three 250 mL beakers water of various temperatures (hot, room temperature, cold) clock/timer data table

Procedures:1. Write a hypothesis on the back of your data table.2. Label the beakers and fill them with 100 mL of hot, room temperature, and

cold water.3. Place a drop of food coloring into each of the beakers.4. Each member of the group should rate how much the food coloring has

diffused in the beaker over a ten minute period of time: 1 = small amount (≈1-33%) 2 = medium amount (≈33-67%) 3 = large amount (≈67-100%).

5. Average your results and create a line graph of your average data with the rating on the y-axis and the timed intervals on the x-axis.

Do not touch/move the beakers once the water and food coloring are in them.

Data Table2 Minutes 4 Minutes 6 Minutes 8 Minutes 10

MinutesH R C H R C H R C H R C H R C

Member

1

2

3

4

5

Average

Discussion Questions

1. What patterns or trends did you notice?

2. What factors could have impacted the accuracy of your data?

3. Did your data support your hypothesis? Explain your reasoning.

Kinetic Theory of Matter states that all of the

particles that make up matter are constantly in motion all particles in matter have kinetic energy

energy is transferred when particles collide with one another

helps explain the different states of matter

PhET

What do you think happenswhen a slow moving particle

is struck by a fast moving one?

Temperature the quantity that tells how hot or cold

something is compared to a standard the average kinetic energy of all the particles

in an object not determined by how much of a substance you have

Higher average kinetic energy (particle movement) results in higher temperatures, while lower average kinetic energy (particle movement) results in lower temperatures

measured using a thermometer

Thermometer an instrument for measuring temperature typically a thin glass tube filled with a liquid

(alcohol or mercury) mercury is not typically used anymore

because of its impact on the environment works because of thermal expansion consist of three different scales:

Fahrenheit (0F) Celsius (0C) Kelvin (K)

Why is alcohol used in thermometers instead of water?

Temperature Scales

Which scale is beingrepresented by each

thermometer?

Waterfreezes

320 00 273

Roomtemperature

680 200 293

Waterboils

2120 1000 373

Fahrenheit Celsius Kelvin

The Kelvinscaledoes not

have negativ

enumber

s

Converting Between Scales Celsius to Fahrenheit

Fahrenheit to Celsius

Celsius to Kelvin

Kelvin to Celsius

0C = 5 x (0F - 32) 9

0F = 9 x 0C + 32 5

K = 0C + 273

0C = K - 273

Example

50C 0F

= 9 x + 32 5

0C0F 50C410F

Example

700F 0C

= 5 x ( - 32) 9

0F0C 700F210C

Example

100C K

= + 2730CK 100C283K

Example = - 273

100 K 0C

K0C 100 K-1730C

Combining Different TemperaturesOverview

For this activity you will mix different amounts of hot and cold water.

Materials: 3 - 250 mL beakers 2 - 100 mL graduated cylinder three Celsius thermometers hot and cold water

Procedures:1. Label the three beakers (H, C, M).2. Using the graduated cylinder, measure the amount of cold water

specified by the data table and pour it into the beaker labeled “C.” Measure and record the temperature.

3. Using the graduated cylinder, measure the amount of hot water specified by the table and pour it into the beaker labeled “H.” Measure and record the temperature.

4. Predict what the temperature will be after combining the beakers.5. Pour the hot and cold water into the beaker labeled “M.” Measure and

record the water temperature.6. Repeat steps 2-5 for the remaining mixtures specified by the data

table.

Data Table

Mixture Hot WaterTemperatur

e (0C)

Cold WaterTemperatur

e (0C)

Predicted Mixed

Temperature (0C)

Actual Mixed

Temperature (0C)

100 mL hot;100 mL cold

50 mL hot;150 mL cold

150 mL hot;50 mL cold

Questions1. How does the temperature of the different mixtures

compare to the original temperatures of the water?2. For which mixture did your prediction come closest?3. For which mixture was your prediction farthest off?4. Could the temperature of the mixture (hot and cold) ever

reach the temperature of the hot or cold water? Explain your reasoning.

5. Although the hot water was the same temperature in each beaker, the impact observed when it was combined with the cold water varied. Why did they all have a different effect?

6. What factors could have impacted the accuracy of your data?

7. What did you learn about mixing temperatures from this activity?

8. What would you predict the temperature to be if 200 mL of hot water (≈1000C) is mixed with 50 mL of cold water (≈00C) ? Explain your reasoning.

Heating and Cooling a Metal Strip1. Plug in the hot plate and allow it to heat up for 3-5

minutes.2. Have a conversation with the members of your group

regarding what you think will happen once you heat and cool the metal strip.

3. Using the hot plate, heat the metal strip with the printed side facing upward. It is not necessary to touch the metal strip on the hot plate.

4. Take note of what you observe as the metal strip is heated with the hot plate.

5. Allow the strip to cool for a few minutes.6. Gently rub the metal strip on an ice cube with the

printed side facing upward. 7. Take note of what you observe as the metal strip is

being cooled with the ice.

Discussion Questions

1. What observations did you make after putting the metal strip over the hot plate? Be specific!!!

2. Why/how did this happen?3. What observations did you make after

rubbing the metal strip on the ice cube? Be specific!!!

4. Why/how did this happen?5. What do you think would have happened if it

was heated or cooled to a greater degree?The metal strip is actually know as a bimetal strip.

Thermal Expansion the increase in volume of a substance due to an

increase in temperature – the particles themselves DO NOT expand

as a substance gets hotter the particles move faster and spread out

most matter expands when it’s heated and contracts when it’s cooled Exception - water actually expands as it cools from 40C to

00C different substances expand at different rates gases generally expand or contract more than liquids,

and liquids expand or contract more than solids Example:

Bimetal strips in thermostats

As the particles spread out, the volume of a substance increases. What happens

to the substance’s density?

Thermal Expansion & Contraction(A closer look)

Piece of Metal

Expansion Contraction

Applications of Thermal Expansion and Contraction

Try to apply and/or explain the concepts of thermal expansion and contraction as they pertain to the following examples.

expansion joints in bridges or sidewalks thermometers hard to open jar lid railroad tracks and train derailments telephone/power lines potholes objects filled with gas (tire, balloon, athletic ball,

etc.)What are some personal examples or

experiences with thermal expansion and contraction?

Heat flow or transfer of energy from an object at a higher

temperature to an object at a lower temperature, until thermal equilibrium is reached

matter does not have heat, it has thermal energy typically expressed in units of joules (J) and calories

(cal) Calorie is really a kilocalorie and represents food

energy 4.187 joules = 1 calorie

scientists believed that heat was an invisible, weightless fluid capable of flowing caloric Count Rumford (Benjamin Thompson) challenged the

idea of caloric when he discovered that heat was being produced when holes were drilled into cannon barrels

3 types of heat transfer: conduction, convection, radiation

Why does an ice cube feel cold while a paper cup filled with coffee feels

hot?

Boiling Water in a Paper Cup

Using the Conductometer

1. Place an equal amount of wax in the divots of each rod (A,B,S,N,C).

2. Light the candle.3. With the wax filled divots facing

upward, place the central heating disk directly over the candle.

4. Observe the order in which the wax melts.

Discussion Questions

1. What is the order in which the wax melts.

2. What impacted how quickly the wax melted in each rod?

3. What factors could have impacted the accuracy of your results?

1. Copper (C)2. Aluminum (A)3. Brass (B)4. Steel (S)5. Nickel (N)

Specific Heat Capacity the amount of energy needed to change the

temperature of 1 kg of a substance by 10C how easily substances change temperatures increases as the size of the particles that make up the

substance increase the higher the value the more energy and the longer it

takes to heat up or cool down e.g. – with a specific heat of 0.11 cal/g0C (444 J/kg0C), nickel

will take longer to heat up and cool down compared to copper which has a specific heat value of 0.09 cal/g0C (387 J/kg0C)

can be used to help calculate heat lost or gained by a substance formula: mc∆T

Explain how/why bodies of water in our area are warmer

towards the end of the summer compared to the beginning.

Table of Specific Heat Values

Substance Specific Heat(cal/g0C)

Specific Heat(J/kg0C)

Air 0.25 1,046

Aluminum 0.22 899

Copper 0.09 387

Glass 0.20 837

Ice (-200C to 00C) 0.50 2,090

Iron 0.11 448

Mercury 0.03 138

Ocean Water 0.93 3,894

Water 1.00 4,187

Wood 0.42 1760

Thermal Energy vs. Temperature vs. Heat

Thermal Energy

Temperature Heat

the total energy of the particles in a

substance

a measure the average kinetic energy of all the

particles in an object

the transfer of energy between

objects that are at different

temperatures

expressed in joules expressed in degrees Fahrenheit,

Celsius, or Kelvin

expressed in joules or calories

varies with the mass and temperature of

a substance

does not vary with the mass of a

substance

varies with the mass, specific heat

capacity, and temperature change

of a substance

Conduction

transfer of thermal energy through a substance, or from one substance to another by direct contact of particles

takes place in solids, liquids, and gases, but takes place best in solids because the particles of a solid are in direct contact with each other Unfortunately for someone, after

being touched, the heat will transfer from the iron to the hand. What are some other real-life examples where heat is transferred by conduction?

Conductors and Insulators Conductors

substances that conduct thermal energy well

particles are close together

different metals are common conductors

Insulators substances that do

not conduct thermal energy well they delay heat transfer

particles are far apart

different plastics are common insulators

What are some common conductors and insulators?

Melting Blocks

Convection transfer of thermal energy through fluids

(liquids or gases) by means of up and down movements called convection currents the circular motion of liquids or gases due to

density differences that result from temperature differences Sea and land breezes result from uneven heating of the

Earth’s surface and the resulting convection currents.

Explain how this happens.

As the air gets heated by the flame, the particles move faster and spread out. This increases the volume of the

air inside the balloon, which lowers the density. This decrease in density

causes the balloon to rise.

Radiation transfer of thermal (radiant) energy as

electromagnetic waves, such as visible light or infrared waves

energy can be transferred through matter or empty space

darker objects absorb more radiant energy than lighter objects

Notice how the visible light from the sun travels through space and heats the Earth.

Calculating Heat – Sample Problem How many joules are needed to raise the

temperature of 100 kilograms of copper from 10 C to 100 C? The specific heat of copper is 387 J/kg·C.

Q = mc∆T

Heat =(100 kg)

Heat = 3,483,000 J

(90 C)

Take thedifference

between 100Cand 1000C

heat massspecificheat

change intemperature

387 J kg·C