. Flashcards
What are the possible dangers of microwaves? (3)
- Can cause MUTATIONS (cancer)/damage cells
- Affect the BRAIN
- Cause INTERNAL HEATING of body tissues
What is the hazard associated with infrared radiation?
Is felt as heat (like in heaters, toasters, grills) so can cause skin BURNS
What are the reasons for some people thinking that microwaves in mobile phones are not hazardous? (3)
- WEAKER radiation than microwave oven
- LOW intensity
- Not ionising
What is the danger of visible light?
Can damage our eyes (e.g. we shouldn’t look directly into the sun)
What are the dangers believed to be associated with the use of mobile phones? (4)
- Affects brain
- Headaches
- Fatigue
- Higher cancer risk
What do the position of lines in the absorption spectrum show? (2)
If there is a shift and whether it’s red-shift or blue-shift
Describe a solid in terms of Flow, Shape, Volume and Density (NB: density relative to a gas)
F= no S= fixed V= fixed D= much higher than a gas
Describe a liquid in terms of Flow, Shape, Volume and Density (NB: density relative to a gas)
F= yes S= fits container shape V= fixed D= much higher than a gas
Describe a gas in terms of Flow, Shape, Volume and Density
F= yes S= fills container shape V= can be changed D= low compared to a solid/liquid
Why do fluids rise when heated? (3)
- Fluids EXPAND when heated because particles move more
- So they take MORE SPACE
- DENSITY DECREASES, rises
Why does the density of a fluid decrease when particles spread out?
The SAME MASS of fluid now occupies a BIGGER VOLUME
Explain evaporation and the cooling effect this causes. Use the kinetic theory. (2)
- WEAK attractive FORCES between the liquid molecules
- FASTER molecules (w/ more Ek) break away and ESCAPE from liquid
Why is the remaining liquid is cooler after evaporation has taken place?
Because the AVG. Ek of the remaining molecules has DECREASED
What features does a car have to keep cool by design? (2)
- Radiator has a large SA,
- A cooling fan that switches on when engine= hot
A motorcycle has cooling fins. What do these do to keep the engine cool?
-Inc. SA of the engine IN CONTACT WITH AIR so faster energy transfer
How does a cooling fan cool the engine?
How does the large SA of the radiator in a car keep cool?
- Inc. AIR FLOW over radiator surface
- Inc. CONVECTION in the air and RADIATION
What is a heat sink and what does it do? (3)
- A METAL PLATE
- Fixed to ELECTRONIC COMPONENT that turns off when too hot
- Inc. SA of the component
How are household radiators engineered to transfer heat quickly? (3)
- Thin
- Flat
- May have fins
Which is typically the most effective: A cavity wall, a solid brick wall, or a double glazed window? How would someone know this?
- A cavity wall
- Has the lowest U-value
What does the rate of temperature change of a substance depend on? (4)
- The energy supplied to it
- Its mass
- Its SHC
- The material it’s made from
How does a storage heater work? (3)
- Uses NIGHT electricity to heat special bricks inside
- ENERGY TRANSFER from bricks keeps room warm
- Bricks= high SHC so they store lots
Why are non-metals insulators and not conductors?
ALL ELECTRONS HELD IN ATOMS
No delocalised electrons
How does energy transfer take place in non-metals and what is this much less effective than?
- Atoms VIBRATE and shake each other
- Than energy transfer by free electrons
