P1 Flashcards
Name the electromagnetic waves (in order of increasing frequency/decreasing wavelength).
Radio Waves Microwaves Infrared Visible Light Ultraviolet X-Rays Gamma Rays
Ronald McDonald Invaded Vegas Using X-Rays Goggles
What is similar about all electromagnetic waves?
They all travel at the same speed through a vacuum.
What do the properties of electromagnetic waves depend on?
Frequency and wavelength
State a property of electromagnetic waves with high frequencies/wavelengths?
They can be harmful to living cells because they have a lot of energy.
What happens when an object absorbs electromagnetic radiation?
The object can heat up and become ionised (If the frequency is high enough).
What is light used for and why? (Other than allowing us to see)
Radio and electrical signals because it can travel very fast.
What is heat a measure of?
Energy.
What happens when a substance is heated?
It gains kinetic energy.
What is temperature?
A measure of the average kinetic energy of the particles of a substance.
How does energy flow with hot and cold objects?
It flows from hot objects to cooler ones.
How does the difference in temperature affect the rate of energy flow.
The greater the difference in temperature… the faster the rate of energy flow/cooling will be.
What is specific heat capacity?
The amount of energy required to heat 1kg of a substance by 1°C
What is the formula for specific heat capacity?
energy = mass * SHC * temperature change q = mcΔt
How much energy is needed to heat 2kg of water from 10°C to 100°C?
q = mcΔt m = 2kg c = 4200 J/kg°C (SHC of water) Δt = 100-10 = 90°C q = 2*4200*90
q = 756,000 J
Why is there no temperature change when substance is changing state?
All the energy is being used to break the intermolecular bonds or all the energy is released to form bonds which stops the temperature going down.
In terms of bonds, what happens to a substance when it is condensing of freezing?
Bonds are forming.
What is specific latent heat?
The amount of energy needed to change the specific state of 1kg of a substance without changing it’s temperature.
What is the specific latent heat of melting?
The energy required to melt 1kg of a substance without changing it’s temperature.
What is the specific latent heat of boiling?
The energy required to boil 1kg of a substance without changing it’s temperature.
NOTE:
Specific latent heat is different for different materials AND boiling and melting.
What is the formula for specific latent heat?
energy = mass * specific latent heat q = mL
Where does conduction occur?
In solids, liquids and gases. Mainly solids though.
What is conduction?
The process where vibrating particles pass on extra kinetic energy to neighbouring particles.
Why do metals conduct heat well?
They have delocalised/free electrons that are able to pass on energy.
Why don’t liquid and gases conduct well?
The particles aren’t as close as in solids so they can’t bump into each other easily.
Where does convection occur?
Liquids and gases
Describe convection currents
- Substance heated up.
- Particles move faster and the substance expands, becoming less dense.
- Warm fluid rises as it is less dense.
- Cooler fluid takes it’s place and the process is continued, creating convection currents.
Why can’t convection occur in solids?
Because the particles can’t move.
State 3 ways in which heat can be transferred?
Radiation, conduction and convection.
How is radiation different from conduction and convection?
- It doesn’t need a medium to travel through.
- It can only occur through transparent substances.
- The amount of radiation absorbed by an object depends on it’s surface colour and texture.
What affects the amount of radiation emitted or absorbed by an object?
The surface colour or texture.
Hotter objects emit ____ heat radiation.
more
Hotter objects emit more heat radiation.
What type of objects are poor absorbers and emitters of radiation? (Reflectors)
white, shiny, smooth
How does an oven work?
- Heat food by infrared radiation.
- Heat is radiated by a grill.
- Absorbed by the surface of the food, increasing kinetic energy.
- Heat energy is then transferred to the centre of the food by conduction and convection.
How does a microwave work?
- Produces microwaves
- Microwaves penetrate about 1cm into the food, absorbed by water or fat, increasing their kinetic energy.
- The energy is then conducted or convected to other parts.
How do you work out the payback time?
payback time = (initial cost/annual saving)
How can you insulate your house?
- Loft insulation
- Hot water tank jacket
- Cavity walls & insulation
- Draught-proofing
- Double glazing
- Thick curtains
What can be used to show where a house is leaking heat?
Thermogram
What is the formula for efficiency?
efficiency = (useful energy output/total energy input)*100
What do sankey diagrams show?
Energy transformation. (Input energy, wasted energy and useful energy)
What are the 3 features/characteristics with waves?
- Amplitude
- Wavelength
- Frequency
What is the formula for wave speed?
speed = frequency * wavelength v = f * λ
How can waves be changed?
Reflection, refraction and diffraction
What is the law of reflection?
angle of incidence = angle of reflection
[INSERT $WAG DIAGRAM OF REFLECTION HERE PLS JOESEPH -dOM]
What is total internal reflection?
When light travels into a material beyond the critical angle of that material and gets reflected back into the material.
What is diffraction?
The spreading out of waves when they pass through a gap or pass an object. [INSERT DIAGRAM(s) OF DIFFRACTION HERE PLS JOESEPH, TRY TO GET AN IMAGE WITH ALL THE TYPES IN -dOM]
What is reflection?
A wave bouncing off a medium. [REFLECTION DIAGRAM]
What is refraction?
When a wave moves from one medium to another with a different density AT AN ANGLE. It causes the wave to change speed and therefore change direction. [REFRACTION DIAGRAM]
What does the amount of diffraction depend on?
The size of the gap relative to the wavelength of the wave. The narrower the gap, or the longer the wavelength, the more the wave spreads.
When light passes into a denser medium, it ______ causing the light to refract _______ the medium.
slows down, towards
