P1 1 Energy Transfer by Heating Flashcards
What is infrared radiation?
It is energy transfer by electromagnetic waves. It can travel through a vacuum therefore doesn’t need particles to move and is heat energy.
What does every object emit?
Infrared radiation
Complete the sentence: The hotter the object, the ___ IR radiation is emitted in a given time.
More
What are electromagnetic waves?
They are electric and magnetic waves that travel through space.
Where is IR radiation found in the electromagnetic spectrum?
The red part.
What does the sun emit?
All types of radiation.
What does the atmosphere not do with IR radiation?
It doesn’t block it.
Explain the greenhouse effect.
• The atmosphere only let’s short wavelength IR radiation through to hear the surroundings. • The surroundings only emit long wavelength IR radiation which don’t get through the atmosphere. • Greenhouse gases such as water vapour, methane, carbon dioxide trap IR radiation causing the earth to become warmer hence Global Warming develops.
What are the best emitters of radiation?
Dark, matt surfaces
What are the best absorbers of radiation? Why?
Dark, matt surfaces as they have more cavities. The radiation reflected hits the surface again.
What are the best reflectors of radiation?
Light, shiny surfaces
What are the three states of matter?
Solid, liquid and gas
Complete this: Solid Flow: Shape: Volume: Density: Compressible: Pressure: Liquid Flow: Shape: Volume: Density: Conpressible: Pressure: Gas Flow: Shape: Volume: Density: Compressible: Pressure:
Solid Flow:✖️ Shape: fixed Volume: fixed Density: much higher than a gas Compressible: ✖️ Pressure:✖️ Liquid Flow:✔️ Shape: fits container shape Volume: fixed Density: much higher than a gas Compressible:✖️ Pressure:✔️ Gas Flow:✔️ Shape: fills container Volume: can be changed Density: low compared to solid or liquid Compressible:✔️ Pressure:✔️
What is the process when a gas changes into a liquid and a liquid changes into a gas?
Gas to liquid: condensation Liquid to gas: vaporisation or boiling
What do we call the process when a liquid turns into a solid and a solid turns into a liquid?
Solid to liquid: melting Liquid to solid: solidifying or freezing
What do we call the process when a solid turns into a gas and a gas turn into a solid?
Solid to gas: sublimation Gas to solid: condensation
Give an example for sublimation.
Dry ice to carbon dioxide
What do all matters have different amounts of?
Energy
Explain the kinetic theory of matter?
• Particles in a solid are held next to each other in fixed positions and vibrate when gaining energy. • Some particles break free into liquid and move about at random whilst in contact. • Soon more break free and turn into a gas. They move faster and are further apart with the most amount of energy hence are less dense.
What are the best conductors?
Metals
Why are metals better conductors than non-metals?
They contain free electron which move about at random and contain positive ions. They collide with each other passing energy.
What process takes place in metals; what is the energy transfer?
Conduction
What happens in conduction?
When the metal is heated at one end, the free electrons at the hot end gain kinetic energy and move faster. They diffuse and collide with other free electrons and ions in cooler parts and therefore the energy is transferred.
What are the best insulators?
Non-metals
What happens to the electrons in non-metals?
All electrons are held in atoms and when energy transfer takes place, atoms only vibrate and shake each other, therefore they are less effective than metals.
What are the best insulators in non-metals?
Fibreglass and wool
Why are fibreglass and wool good insulators?
They contain trapped air between the fibres and trapped air is good at insulating.
What are fibreglass and wool used for?
Lagging water pipes and lost insulation.
What is the best shape for an insulator? Why?
Sphere as it is of lowest surface area: volume ratio and therefore is of a large surface area and prevents heat loss.
What is convection?
It is heat transfer through a liquid or a gas.
Where do convection currents occur?
In fluids (liquid or gas)
What is the process of a convection current?
• A fluid is heated and this makes it less dense hence it rises up. • As it get cooler it starts to sink. • It gets heated again and a circulation is created.
Why does heating fluids make them less sense?
The particles are more further apart and therefore the same mass of the fluid occupies a bigger volume.
Where is convection used and how?
In hot water tanks at home, hot water from the boiler rises to the tank where it rises to the top into the tap.
What happens on a sunny day to lead a sea breeze to occur?
• The ground heats up faster than the sea. • Air above ground warms up and rises. • Cooler air replaces the escaped air as a “sea breeze”
What is evaporation?
When a liquid turns into a gas.
What factors affect the rate of evaporation?
• Increasing the surface area of a liquid. • Increasing temperature of a liquid. • Creating a draught of air across the liquid’s surface.
How does cooling by evaporation take place?
• There are weak attractive forces between molecules in liquids. • When water molecules need to evaporate, they nee extra kinetic energy. • Therefore they take heat energy from the nearest energy source. • The faster molecules with more kinetic energy escape. • They will break free leaving the surface cooler; the average kinetic energy remaining of molecules would have dropped.
What happens in condensation?
Water vapour cools down and turns into water.
What are the factors affecting the rate of condensation?
• Reducing surface temperature • Increasing surface area
What are the factors affecting the rate of energy transfer?
• Object’s mass • Object’s shape • The material object is in contact with • The bigger the temperature difference between an object and it’s surrounding (faster the rate) • Object’s material • Object’s surface area
What makes a vacuum flask a good insulator?
• Silver glass surfaces reduce heat transfer through radiation on outer wall. • Vacuum between two walls of container cuts out conduction and convection. • Plastic cup reduces cooling by evaporation ad conduction. • Glass is a poor conductor therefore reduces conduction. • The spring is plastic therefore is a good insulator.
What is specific heat capacity?
It is the energy needed or energy transferred to 1kg of a substance to raise it’s temperature by 1*C.
If the mass is greater in an object, what happens to the rate at which the temperature increases when heated?
Slower
What does temperature rise depend on?
• The amount of energy supplied to it • The mass of the substance • What the substance is
What is the unit of specific heat capacity?
J/kg/*C
What is the equation used for specific heat capacity?
E = m x c x O (cursive) E stands for energy supplied (J) M stands for mass (kg) C stands for specific heat capacity O stands for temperature change (*C)
What is the triangle like for the equation of specific heat capacity?
E at the top m c and o in order along the bottom
What are storage heaters?
• They use off-peak electricity to store energy in special bricks. • They have a high specific heat capacity hence keeps the heat longer.
What is payback time?
The time taken to recover the up-front costs from savings on fuel bills.
What is the formula for payback time?
Cost / annual savings
What do U-values tell us?
It gives a measure of how well a building keeps heat inside.
What is the unit of U-Values?
W/m2/*C
What is the definition of a U-value?
Energy passing out per square meter for each 1*C temperature difference.
What does it mean when something is of a lower U-value?
It is more effective as an insulator.
What are the ways of keeping a house warm, and how?
Loft insulation: fibreglass reduces the the of energy through roof. Trapped air reduces conduction. Cavity wall insulation: space between the two layers of brick making up the wall is known as the cavity. Insulation is pumped into the cavity and traps air therefore reduces energy transfer through conduction. Aluminium foil: placed between radiator panel and wall and reflects radiation away from wall. Double-glazed windows: two panels of glass are present and dry air or a vacuum is in between and reduces conduction and convection.
How do solar heating panels work?
• It uses solar energy to heat water. • It is connected to the heat exchanger. • It has matt black copper pipes to absorb more heat and contains a solution with antifreeze which lowers the freezing point.
What are the advantages and disadvantages of solar heating panels?
Disadvantage: expensive and only works on sing days Advantage: renewable and no fuel is needed
When you put hand sanitiser, how does it link with the cooling of evaporation?
In order to escape the particles need extra energy hence take it from the nearest source (hand) and break free.
What do the particles from water escape into?
Vapour
