Heat

Heat transfer through conduction, convection and Radiation.

Grade 7 Science

Concept PresentationInitha Subramaniam OISE/UT

Instructors: Dr. Marty Zatzman and Janine Extavour

Overview• Curriculum Expectations.• Prior knowledge on the topic.• Misconceptions.• Demonstrations / Experiments.• Societal issues that can be discussed in class.• Safety considerations.• 5 day lesson plan.• Placement of the concept within the unit.• Place in the Curriculum.• Advance preparations/ materials.• Assessment (A) Evaluation (E).• Learning styles (LS) / Multiple intelligence (MI).• Differentiated Instruction.• References

Grade 7 Heat UnitCurriculum Expectations

Fundamental concept: Energy transfer

Big idea: Heat is a form of energy that can be transformed and transferred. These processes can be explained using the particle theory of matter.

Overall Expectations:2. Investigate ways in which heat changes substances, and

describe how heat is transferred.3. Demonstrate an understanding of heat as a form of energy

that is associated with the movement of particles and essential to many processes within the earth’s systems.

Specific Expectations

3.1 Use the particle theory to compare how heat affects the motion of particles in solids, liquids and gases.

3.3 Use particle theory to explain the effects of heat on volume of solids, liquids and gases.

3.4Explain how heat is transmitted through conduction.3.5 Explain how heat is transmitted through convection.3.6 Explain how heat is transmitted through radiant energy.2.4 Use scientific inquiry and experimentation skills to investigate heat transfer

through conduction, convection and radiant energy.2.5 Use appropriate science and technology vocabulary, including heat,

temperature, conduction, convection and radiation in oral and written communication.

3.7 Describe the role of radiation in heating and cooling the earth, and explain how greenhouse gases affect the transmission of radiated heat through the atmosphere.

Grade 9 Earth and Space: Climate ChangeOverall expectations: D1. Analyze some of the effects of climate change around the

world, and assess the effectiveness of initiatives that attempt to address the issue of climate change.

Specific Expectations:D3.2 Describe and explain heat transfer in the hydrosphere and

atmosphere and its effects on air and water currents.D3.3 Describe the natural green house effect.

Day 1. solid particles

• Held tightly and packed fairly close together - they are strongly attracted to each other.

• Have fixed positions but they do vibrate.• Expands when heated.

Liquid Particles

• Fairly close together with some attraction between them.

• Able to move around in all directions but movement is limited by attractions between particles

Gas Particles

• Have little attraction between them.• Free to move in all directions and collide with each

other and with the walls of a container and are widely spaced out.

Prior Knowledge

kinetic Energy: All moving objects have this type of energy.

Particles moving faster = greater kinetic energy.Particles moving slower = slower kinetic energy.When particles move and collide they speed up

or slow down. Temperature: measures the average kinetic

energy of particles

What happens when particles are heated

• When particles are heated they go through a change of state.

• Heat : Transfer of energy from a particle of a warmer object to a particle of a cooler object.

• When heating an object energy is transferred to the particles of the object.

Change state of matterand how is thermal energy transferred

Experiment : Expansion and Contraction of particles.

Expansion: balloon fasten on a volumetric flask set inside a beaker of hot water.

Contraction: Balloon fasten on a volumetric flask set inside a beaker of ice water.

Note to self

Give the class candies to earn their votes.

Mmmmm ……. Candies make everything better.

You tube http://www.youtube.com/watch?v=VzE_IPedujc&feature=related

Day 2: Making soup to demonstrate conduction

Conduction happen when two substances are touching. The particles of one substance collides with particles of another substance or with each other. Thermal energy is transferred. Metals good conductors.

Day 3: Convection current when boiling water

Convection is the movement of gases or liquids from a cooler area to a warmer area.

Example: cooking soup on the stove.The warmer soup moves up from the heated area at the bottom

of the pan to the top where it is cooler. The cooler soup then moves down to take the warmer soup's

place. The movement is in a circular pattern within the pan.

Day 4: Radiant energy• Radiation is the transfer of heat energy through empty space. • Energy travels from the sun to the earth by means of

electromagnetic waves. • Shorter wavelength = higher energy• Darker-colored objects absorb more visible radiation thus

becoming good insulators of thermal energy.• whereas lighter-colored objects reflect more visible radiation. • Every surface on earth absorbs and reflects energy at varying

degrees, based on its color and texture.

Common misconceptions

1. Particles get bigger when they are heated.2. Convection current forms only when a substance is

boiled.3. At night time land and water cool down at the same

rate.4. All dark coloured objects are good insulators of

thermal energy.

Misconception 1Particles get bigger when heated.

• Scientifically incorrect.• Heat energy flows through a region of high temperature to a

region of low temperature when the particles collide. • This is the process of conduction.• When particles carry thermal energy they do not get bigger

but take up more space (expand slightly).

Ball and ring experiment to explain conduction. The sequence used to heat up the objects1. RT ball and RT ring = 2. Hot ball and RT ring =3. Hot ball and hot ring =4. RT ball and hot ring =

Explain the observations in terms of the motion of the metal particles in the ball and ring.

Make statements describing the sizes in relation to the ball and ring at different temperatures.

(RT= Room Temperature)

Experiment : Testing for particle expansion

Misconception 2Convection current forms only when a

substance is boiling.• When fluid or gas particles are warm they expand and become

less dense in mass. • They rise from the bottom moving upwards towards the surface . • As warm particles reach the top layer they push down the colder

particles (greater in mass) down. • The process continues in a cycle .• However cooling particles from above will also produce

convection current.• Both warm gas and fluid particles transfer thermal energy

through convection current.

Experiment: Convection in warm water.• Plastic container with RT water supported by four

Styrofoam cup.• Place a drop of red food coloring at the bottom of

the water.• Place blue coloured ice cubes at the top• Place a cup of hot water at the bottom of the food

coloring.• Observe and discuss results.

Misconception 3Gases, liquids and solids heat up at the same rate and

release thermal energy at the same rate

Demo = www.youtube.com/watch?v=gM0d3fGew-0

Land and Sea Breeze• Convection currents are noticeable near the ocean, large lake,

or other appreciable area of water. During the day:• land heats faster than water, so the air over the land becomes

warmer and less dense. • It rises and is replaced by cooler, denser air flowing in from

over the water. This causes an onshore wind, called a sea breeze.

During Night time:• land cools faster than water.• warmer air over the water rises and is replaced by the cooler,

denser air from the land, creating an offshore wind called a land breeze.

• Demo = http://www.youtube.com/watch?v=xlqc3YJAmiQ&feature=related

Misconception 4All black objects are good insulators.

Radiant energy travels through empty space.

For a black coloured object to become an insulator of thermal energy it as to be left out side in direct view of sunlight or near a roaring flame but not touching the flame.

A black coloured object left under room temperature conditions will not turn into an insulator of thermal energy.

Ex: A plastic bottle filled with warm water and wrapped in black cloth will not be a good insulator of thermal energy.

Experiment : Not all black objects are insulators Part A: students make data tables to record the time and temperature.• Fill 3 pie pans to the same level, one with dark soil, one with light sand, and

one with water.• Place the pie pans under a table lamp • Place a thermometer into each pie pan. • measures the temperature just under the surface of the substance .• Record the starting temperatures on the data table.• Turn on the lamp and record the temperature of each substance every

minute for ten minutes.• At the end of ten minutes, turn the lamp off.

Part B Repeat the entire procedure but remove the lamp. Discuss the variations in the results.

Day 5: Managing the transfer of thermal energy

Divide the class into groups of 5 and ask the students to implement drama in science and create a Talbot on the concepts learned.

The students can also create a story by each person saying a sentence based on the prior knowledge of the concepts.

Students can work in pairs and play “Show it in action”. Student A will start with a short sentence based on the concept. Student B will show the action for it and say another sentence. Student A will do that action and so on.

Talk about methods used to control the transfer of thermal energy.

Design challenge is introduced: Building a thermos using a 2L pop bottle which will keep water above 75 degrees for two hours.

Societal issues that can be discussed in class

• Relate concepts to the function of steam engines.• Dangers of rising sea levels due to global warming.• Uses of some plastics as thermal energy conductors in the

electronics industry.• Discuss how convection can be used to explain the process of

releasing smoke through a chimney. • Formation of igneous rock .• Theory behind using certain coloured clothing in countries

that receive high amounts of sunlight. • The purpose of using certain materials by fire fighters when

fighting extreme fires.• Annotated References.

Refer to the handout

• Placement of the concept within the unit.• Place in the Curriculum.• Advance preparations/ materials.• Assessment (A) Evaluation (E).• Learning styles (LS) / Multiple intelligence (MI).• Differentiated Instruction.

Safety considerations:

• Show knowledge necessary to use the materials, and tools involved in experiments.

• The skills needed to perform tasks efficiently and safely.• Maintain a well organized and uncluttered work space.• Follow established safety procedures.• Identify possible safety concerns.• Carefully follow the instructions and example of the teacher,• Consistently show care and concern for their safety and that of

others.• Use fire safety procedures when using candles.• Wear safety goggles at all time.

Thank You

Special thank you to my mentor Roberta. Thank you for giving me constructive feedback and helping me set up the demonstrations.