Unit 3 15 Flashcards
Conduction
When heat is transferred between neighbouring particles
Examples of insulators
Wood,fibreglass,wool
How is heat loss reduced in the home?
Using double glazing,fibreglass insulation in lofts
Convection
Occurs in liquids and gases (fluids) when particles move,carrying heat with them
How do convection currents spread heat in fluids?
When they are heated from the base or cooled from the top
How are unwanted transfers of heat energy in the home reduced?
Using draughty excluders,
keeping doors and windows closed,
blocking unused fireplaces
When is radiation emitted?
When infrared waves transfer heat energy from the surface of objects.
Which objects radiate energy more quickly?
Hot/cooler
Hot
When do objects cool down?
If they radiate heat
When do objects warm up?
If they absorb radiation
Which radiates more energy in a given time?
Black matt objects // shiny objects
Black Matt
How are heat losses in the home reduced?
By putting foil on walls behind radiators
What does a black surface do?
Helps a cool object heat up quickly,
Allows a hot object to cool down quickly
Payback time =
Cost of installation / annual savings
What is payback time?
The time for the cost of installing energy saving measures to match the savings they generate
How can householders save cost by reducing energy losses?
Reducing heat losses
Using efficient equipment
Using equipment more efficiently
Why is double glazing’s payback time very long?
Expensive to install,does not reduce heat losses much
What do U-Values do?
Measure the rate of heat loss through a material
Why do good heat conductors like metals have a high U-value?
They transfer heat quickly
What does a low U-value mean?
Heat is transferred more slowly through the material
Why do architects aim to specify materials with low U-values?
To reduce heat losses in winter and so keep a home warm
Why is it more important to use materials with a low U-value for walls than for Windows?
Walls-larger surface area so more heat is lost through them
What can closed air systems in homes lead to?
A build up of indoor pollutants
Name examples of indoor air pollutants:
Dust,mound and spores,pollen,smoke,fumes from household products,carbon monoxide
What are symptoms of exposure to high levels of indoor pollution?
Asthma Headaches Tiredness Nausea Itchy nose Sore throat
What are the effects of mould,spores,dust?
Allergic reactions,itchy nose
Effects of soot and smoke?
Lung damage,sore throat,watery eyes
Effects of fuels and cleaning products?
Nausea,tiredness,headaches
Effects of carbon monoxide?
Tiredness,death
What can exposure to hazardous chemicals cause?
Dizziness,rashes,headaches
Harmful
Damage health
Irritant
Rashes. Same as harmful
Don’t touch with bare skin,don’t inhale/eat or drink
Corrosive
Chemical burns.
Use gloves/eye protection
Environmental hazard
Dispose carefully.
Can harm animals/plants
Flammable
Keep sealed/away from heat sources
Toxic
Poisonous.
Use cloves,don’t drink
When does incomplete combustion occur?
When a fuel is burned without enough oxygen
What does incomplete combustion produce?
Carbon monoxide and soot
Why is carbon monoxide dangerous?
It binds to haemoglobin in red blood cells—
replaces the oxygen in your red blood cells
What is the chemical reaction for incomplete combustion?
Hydrocarbon fuel + oxygen —> carbon dioxide + water + carbon monoxide + carbon
How is incomplete combustion different to complete combustion?
It releases less energy
Very dangerous-carbon monoxide gas is poisonous
How can you prevent carbon monoxide poisoning?
Regularly servicing gas/oil boilers helps ensure they are properly ventilated and performing complete combustion
What is radon gas?
A radioactive gas that seeps naturally out of rocks like granite.
Can cause cancer
What do the rocks that radon seeps under contain?
Uranium,plutonium
What can radioactivity in radon gas do to your body?
Damage cells in lungs-become cancerous
Why are smokers affected more than non smokers by lung cancer caused by radon gas?
Cells in lungs are already damaged from smoking
How can radon levels be reduced?
By ventilating the building
Why isn’t radon gas a pollutant in all parts of the country?
Radon gas only seems out of certain types of rocks which are only found in some parts of country
Flammable
Keep sealed/away from heat sources
Toxic
Poisonous.
Use cloves,don’t drink
When does incomplete combustion occur?
When a fuel is burned without enough oxygen
What does incomplete combustion produce?
Carbon monoxide and soot
Why is carbon monoxide dangerous?
It binds to haemoglobin in red blood cells—
replaces the oxygen in your red blood cells
What is the chemical reaction for incomplete combustion?
Hydrocarbon fuel + oxygen —> carbon dioxide + water + carbon monoxide + carbon
How is incomplete combustion different to complete combustion?
It releases less energy
Very dangerous-carbon monoxide gas is poisonous
How can you prevent carbon monoxide poisoning?
Regularly servicing gas/oil boilers helps ensure they are properly ventilated and performing complete combustion
What is radon gas?
A radioactive gas that seeps naturally out of rocks like granite.
Can cause cancer
What do the rocks that radon seeps under contain?
Uranium,plutonium
What can radioactivity in radon gas do to your body?
Damage cells in lungs-become cancerous
Why are smokers affected more than non smokers by lung cancer caused by radon gas?
Cells in lungs are already damaged from smoking
How can radon levels be reduced?
By ventilating the building
Why isn’t radon gas a pollutant in all parts of the country?
Radon gas only seems out of certain types of rocks which are only found in some parts of country
