Unit 3 - Heat and Temperature

Unit Outcomes

Students will:

1. Illustrate and explain how human needs have led to technologies for obtaining and controlling thermal energy and to increased use of energy resources

• investigate and interpret examples of heat-related technologies and energy use in the past (e.g., investigate uses of heat for domestic purposes, such as cooking or home heating, and for industrial processes, such as ceramics, metallurgy or use of engines)

• trace linkages between human purposes and the development of heat-related materials and technologies (e.g., development of hair dryers and clothes dryers; development of protective clothing, such as oven mitts, ski suits and survival clothing)

• identify and explain uses of devices and systems to generate, transfer, control or remove thermal energy (e.g., describe how a furnace and wall thermostat keep a house at a constant temperature)

• identify examples of personal and societal choices in using energy resources and technology (e.g., identify choices that affect the amount of hot water used in their daily routines; identify choices in how that water is heated)

2. Describe the nature of thermal energy and its effects on different forms of matter, using informal observations, experimental evidence and models

• compare heat transmission in different materials (e.g., compare conduction of heat in different solids; compare the absorption of radiant heat by different surfaces)

• explain how heat is transmitted by conduction, convection and radiation in solids, liquids and gases

• describe the effect of heat on the motion of particles; and explain changes of state, using the particle model of matter

• distinguish between heat and temperature; and explain temperature, using the concept of kinetic energy and the particle model of matter • investigate and describe the effects of heating and cooling on the volume of different materials, and identify applications of these effects (e.g.,use of expansion joints on bridges and railway tracks to accommodate thermal expansion)

3. Apply an understanding of heat and temperature in interpreting natural phenomena and technological devices • describe ways in which thermal energy is produced naturally (e.g., solar radiation, combustion of fuels, living things, geothermal sources and composting)

• describe examples of passive and active solar heating, and explain the principles that underlie them (e.g., design of homes to maximize use of winter sunshine)

• compare and evaluate materials and designs that maximize or minimize heat energy transfer (e.g., design and build a device that minimizes energy transfer, such as an insulated container for hot drinks; evaluate different window coatings for use in a model home)

• explain the operation of technological devices and systems that respond to temperature change (e.g., thermometers, bimetallic strips, thermostatically-controlled heating systems)

• describe and interpret the function of household devices and systems for generating, transferring, controlling or removing thermal energy (e.g., describe in general terms the operation of heaters, furnaces, refrigerators and air conditioning devices)

• investigate and describe practical problems in controlling and using thermal energy (e.g., heat losses, excess energy consumption, damage to materials caused by uneven heating, risk of fire)

4. Analyze issues related to the selection and use of thermal technologies, and explain decisions in terms of advantages and disadvantages for sustainability

• identify and evaluate different sources of heat and the environmental impacts of their use (e.g., identify advantages and disadvantages of fossil fuel use; compare the use of renewable and nonrenewable sources in different applications)

• compare the energy consumption of alternative technologies for heat production and use, and identify related questions and issues (e.g., compare the energy required in alternative cooking technologies, such as electric stoves, gas stoves, microwave ovens and solar cookers; identify issues regarding safety of fuels, hot surfaces and combustion products)

• identify positive and negative consequences of energy use, and describe examples of energy conservation in their home or community

Topic 1

Using Energy From Heat

Key Concept

Humans have always needed thermal energy to survive and thrive. Over time, technologies were developed to meet these needs more efficiently and effectively.

Thermal Energy, heat and infrared radiation are all the same.
We have always used heat in different forms and technology has changed the way we get our heat energy.

Heat-related technologies from the past

Cooking

Early humans used fire to cook food, which improved nutrition and safety.

Home heating

Early civilizations used wood fires and fireplaces for warmth during cold seasons.

Industrial processes

Ceramics: Clay pots fired in kilns hardened for durability.
Metallurgy: The use of heat to melt and shape metals (e.g., forging swords or tools).
Engines: The steam engine in the Industrial Revolution powered trains and factories.

Turn and talk

How did these technologies improve human life at the time?

Links Between Human Needs and Heat-Related Technologies

Key Concept

Human needs (comfort, safety, efficiency) drive innovation in thermal technologies.

Technologies evolve to solve specific problems.

Hair dryers

Developed to speed up hair drying using electrical heating coils and air flow.

Clothes dryers

Designed to dry clothes efficiently using heated air.

protective clothing

Oven Mitts: Use insulating materials (e.g., silicone or heat-resistant fabric) to protect hands from burns.

Ski Suits: Made with synthetic, insulated materials to retain body heat in cold environments.

Survival Gear: Heat-reflective blankets and thermal suits used in extreme cold conditions.

Key Question

How do these devices reflect our needs for comfort, safety, and convenience?

Devices and Systems to Generate, Transfer, Control, or Remove Thermal Energy

Key Concept

Modern devices and systems are designed to regulate thermal energy.

These devices either generate, transfer, control, or remove heat.

Furnace and thermostate

How it works: A thermostat senses the air temperature in a home and signals the furnace to turn on or off to maintain a set temperature.

Refrigeration (remove heating)

How it works: Refrigerators remove heat from inside the unit and release it outside to keep food cool.

Heat transfer in cooking

Stove Elements: Transfer heat directly to a pot or pan.

Microwaves: Use radiation to excite water molecules in food, producing heat.

Personal and Societal Choices in Using Energy Resources and Technology

Key Concept

The way we use thermal energy and energy resources reflects personal choices and societal habits.

These choices can impact energy efficiency and sustainability.

Personal choices

hot water use

Taking shorter showers reduces the amount of hot water used.

Turning off the hot water tap when brushing teeth saves energy.

how water is heated

- Options: Gas heaters, electric heaters, solar water heating systems.
- Example: Choosing a solar heater reduces environmental impact.

Societal Choices

Improving insulation in homes reduces the need for constant heating.
Public policies promoting energy-efficient devices (e.g., Energy Star-rated appliances).

Summary Questions

1) Why do humans develop heat-related technologies?

2) What are some examples of technologies that generate, transfer, or control heat in daily life?

3) How can personal choices impact energy use and sustainability?

Topic 2

Measuring Temperature - The Nature of thermal energy

Heat conduction

Conduction is the transfer of heat through direct contact. Some materials conduct heat better than others.

- Metal (good conductor): A metal spoon in a hot pot heats up quickly.
- Wood or plastic (poor conductor): A wooden spoon stays cool when placed in the same pot.

Radiant heat absorption

Radiation is heat transferred through electromagnetic waves, like sunlight or fire.

Different surfaces absorb radiant heat at different rates.

Examples:
- Dark surfaces: Absorb more heat (e.g., wearing a black shirt on a sunny day feels hotter).
- Light/reflective surfaces: Absorb less heat (e.g., wearing a white shirt keeps you cooler).

Heat vs. Temperature

Temperature is the average kinetic energy of a substance.

Heat is the total kinetic energy of a substance.

Heat Transmission in Different Materials

Key Concept

Heat is transferred through materials at different rates depending on their properties.

Measuring Temperature

Temperature can show how hot or cold something is.
Touch and sight can help us determine the temperature of something, but these methods are subjective.

Thermometers

Thermo = related to heat
Meter = method of measurement
Galileo invented the first thermometer around 1600.
The first precise thermometers were created by Ferdinand II of Tuscany.
The most commonly used temperature scale was created by Anders Celsius in 1742.

Temperature Scales

Celsius based his scale on the properties of water at sea level:

0°C – the temperature at which ice melts.
100°C – the temperature at which water boils.

The space between these points was divided into 100 equal units.

Pressure and Temperature

High Pressure

High pressure can allow ice to melt at lower temperatures than 0°C.
- Example: Skating on ice – the pressure of the skate blade lowers the melting point of ice, creating a thin layer of water that reduces friction.

Low pressure

Low pressure can allow water to boil at a lower temperature than 100°C.
- Example: Water boils faster at higher altitudes. Such as on K2 where air pressure is lower.

Impurities

Impurities affect freezing and boiling points as well:
- Example: Adding salt to water lowers its freezing point, which is why salt is spread on icy roads in winter.

Absolute Zero is the coldest possible temperature; -273.15˚C

Lord Kelvin developed the a scientific scale based on Absolute Zero

- 0˚ C= 273.15K

How Heat is Transmitted

Conduction

Definition: Heat transfer through solids, where particles collide and transfer energy.

Examples:
- A frying pan heats up when placed on a stove.
- Walking barefoot on hot sand transfers heat to your feet.

Convection

Definition: Heat transfer in liquids and gases where warmer, less dense particles rise, and cooler, denser particles sink.

Examples:
- Boiling water: Heat moves in circular currents (convection currents).
- A hot air balloon rises as the air inside is heated and becomes less dense.

Radiation

Definition: Heat transfer through electromagnetic waves (no particles required).
Examples:
- Feeling warmth from the Sun.
- Heat from a campfire warming your hands.

Effect of Heat on Particle Motion and Changes of State

Key Concept:

Adding or removing heat affects the motion of particles in matter and can cause changes in state.

Particles move faster when heated (more kinetic energy) and slower when cooled.

Examples:
- When water is heated, its particles move faster, and it boils (turns into gas).
- When water is cooled, its particles slow down, and it freezes (turns into solid).

Changes of State (The Particle mode of matter)

Solid to liquid (melting): Particles gain energy and move more freely.

Liquid to gas (evaporation/boiling): Particles gain even more energy and move far apart.

Gas to liquid (condensation): Particles lose energy and come closer together.

Liquid to solid (freezing): Particles lose more energy and vibrate in fixed positions.

Effects of Heating and Cooling on Volume

Key Concept

Heating and cooling materials can cause them to expand or contract due to particle motion.

Volume = The amount of space occupied by any three-dimensional solid.

Thermal Expansion

Definition: When materials are heated, particles move faster and spread apart, causing the material to expand.

Bridge Expansion joints

Gaps allow the bridge to expand on hot days without breaking.

Railway Tracks

Tracks are built with small gaps to prevent buckling from heat expansion.

Balloon in the Sun

A balloon expands as air inside heats up and particles spread apart.

Thermal Contraction

Definition: Cooling causes particles to slow down and come closer together, shrinking the material.

Examples:

A metal lid on a jar shrinks slightly when cooled, making it harder to open.
Power lines sag in summer (expansion) and tighten in winter (contraction).

Summary questions

1) What are the three ways heat can be transmitted? Provide examples for each.

2) How does heat affect the motion of particles in a solid, liquid, or gas?

3) What is the difference between heat and temperature?

4) How does heating or cooling cause materials to expand or contract? Give examples of this in real-life applications.

Topic 3

Applying Heat and Temperature: Natural Phenomena and Technological Devices

Reminder

Heat: Transfer of thermal energy between objects of different temperatures.

Temperature: A measure of the average kinetic energy of particles in a substance.

Natural production of thermal energy

geothermal sources

Heat from Earth’s interior (e.g., hot springs, geysers, and volcanic activity).

composting

Decomposition of organic materials generates heat due to microbial activity.

Solar Radiation

The Sun’s energy reaches Earth as electromagnetic waves.

Drives weather, supports life, and powers the water cycle.

combustion of fuels

Burning fuels (e.g., wood, coal, natural gas) releases thermal energy.

living things

Animals produce heat through metabolism (e.g., body warmth in mammals).

passive/active solar heating

passive

Utilizes building design to collect and distribute heat from sunlight.

Example: Large south-facing windows, thermal mass (e.g., concrete, stone).

active

Uses mechanical devices to capture and circulate solar energy.

Example: Solar panels with water or air circulation systems.

Influences

Absorption (albedo) - Dark surfaces absorb thermal energy better.
Insulation - Prevents heat loss to the environment

maximizing and minimizing heat transfer

maximized

Use of conductive materials (e.g., metal pots for cooking).

minimized

Insulators like foam, fiberglass, and vacuum-sealed containers.

technological devices responding to temperature changes

thermometers

Liquid-in-glass thermometers - Expansion of liquid due to heat

Digital thermometers - Use sensors to measure temperature changes

bimettalic strips

Bimetallic Strips

Made of two metals that expand at different rates when heated.

Used in thermostats.

thermostatically controlled systems

Automatically regulate temperature (e.g., home heating systems).

household devices for thermal energy

Key Question: How do household devices generate, transfer, control, or remove thermal energy?

Focus Areas:

Operation of common thermal energy devices.

Problems in controlling and using thermal energy effectively.

Heaters and furnaces

Function: Generate and transfer heat to maintain a comfortable indoor temperature.

How They Work:

Heaters: Use electricity or combustion to produce heat.

Furnaces: Burn fuel (natural gas, oil, propane) or use electricity to heat air, distributed through ducts.

Thermal Energy Transfer: Conduction (metal components), convection (warm air circulation).

refrigerator

Function: Remove heat to keep food cool and prevent spoilage.

How They Work:

Refrigerant absorbs heat inside the fridge and releases it outside.
Uses a compressor, evaporator, and condenser for heat transfer.

air conditioner

Function: Cool indoor spaces by removing heat from the air.

How They Work:

Similar to a refrigerator but designed for larger spaces.
Heat is absorbed indoors and released outside.

Practical Problems with Thermal Energy

heat loss

Problem: Heat escapes through walls, windows, or poorly insulated areas.

Impact: Increases energy consumption and costs.

Solutions:

Add insulation.
Use weatherstripping on doors and windows.

excess energy consumption

Problem: Overuse of heating or cooling systems leads to high energy costs.

Impact: Strain on energy resources, higher carbon footprint.

Solutions:

Set thermostats to energy-efficient temperatures.
Use programmable thermostats.

uneven heating

Problem: Certain areas or materials heat unevenly, causing damage or discomfort.

Examples:

Uneven cooking in ovens.
Materials warping or cracking due to thermal stress.

risk of fire

Problem: Poor maintenance or improper use of thermal devices increases fire risks.

Examples:

Overloaded electrical circuits.
Flammable materials near heaters.

Solutions:

Regular maintenance.
Follow safety guidelines for devices.

thermal energy control and efficiency

Heaters and Furnaces:

Clean filters regularly.
Use energy-efficient models.

Refrigerators:

Keep seals tight to prevent heat exchange.
Avoid overloading to ensure proper airflow.

Air Conditioners:

Clean condenser coils and replace filters.
Close windows and doors when in use.

General:

Use insulation to retain heat in winter and block heat in summer.
Seal gaps in walls, doors, and windows to minimize energy loss.

Discussion Questions

How does a refrigerator differ from a furnace in how it handles thermal energy?
What are some examples of heat loss in your home?
How can we reduce the risk of fire while using thermal devices?

Thermal Technologies and Sustainability

Topic 4

Thermal Technologies and Sustainability

Key Question: How do our choices in heat sources and technologies impact the environment and sustainability?
Focus Areas:
1. Different sources of heat and their environmental impacts.
2. Comparing energy consumption of heat technologies.
3. Positive and negative consequences of energy use.

Sources of Heat

Fossil Fuels

Examples: Coal, oil, natural gas.
Advantages:
- Reliable and widely available.
- High energy output.
Disadvantages:
- Produces greenhouse gases.
- Nonrenewable—limited supply.
- Contributes to climate change.

Renewable sources

Examples: Solar, wind, geothermal, biomass.
Advantages:
- Sustainable and abundant.
- Produces little or no greenhouse gases.
Disadvantages:
- Initial costs can be high.
- Dependent on weather and location.

Comparing Heat Technologies

Energy Consumption

Electric Stove:

- Uses electricity (can come from renewable or nonrenewable sources).
- Higher long-term costs if using nonrenewable electricity.

Gas Stove:

- Uses natural gas (nonrenewable).
- More efficient for cooking but emits greenhouse gases.

Microwave Oven:

- Fast and energy-efficient for small meals.
- Limited to specific types of cooking.

Solar Cooker:

- Renewable and environmentally friendly.
- Limited by weather and time of day.

Environmental Impacts

Fossil fuels: Air pollution, habitat destruction, carbon emissions.
Renewable sources: Minimal pollution but potential for habitat disruption (e.g., hydroelectric dams).

Safety Concerns

Gas leaks and combustion risks.
Hot surfaces and burns.
Toxic combustion products.

Consequences of Energy Use

Positive Consequences:

Provides comfort, cooking, and warmth.
Enables industrial and technological advancements.

Negative Consequences:

Air pollution and greenhouse gas emissions.
Depletion of nonrenewable resources.
Health risks from poor air quality.

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