key words

accuracy - result that is close to true value

interval - quantity between readings

precision - all the results are very close to eachother

range - minimum and maximum values

resolution - smallest change in the quantity being measured

repeatable - get the same result with same method

reproducible - get the same results with a different method / someone else doing it

uncertainty - interval within which the true interval can lie

measurement error - measure something wrong

random error - reading is different every time

systematic error - a constant is off, getting the same reading each time but it’s wrong

zero error - reading doesnt start at 0

conductor - material that allows heat energy to move through

insulator - material in which heat energy doesnt move freely

chapter 2 - energy transfer by heating

2.1 energy transfer by conduction

• metals conduct energy better than non metals

• copper is a better conductor than steel

• glass conducts better than wood

• the energy transfer by conduction through a material depends on it’s thermal conductivity

• the greater the thermal conductivity, the more energy per second it transfers via conduction

• good insulators have low thermal conductivity, so that there is as little energy transfer through them

• the more the atoms vibrate, the hotter the substance is

• energy transfer per second depends on:

  • temp difference across the material

  • thickness of the material

  • thermal conductivity of the material

2.2 + 2.3 infrared radiation (IR)

• the higher the temperature, the more IR radiation it emits

• all objects absorb and emit IR radiation

• a perfect black body absorbs all radiation it is hit with

• an object which has a constant temperature emits radiation across a continuous range of wavelengths

• the temperature of an object increases when it absorbs more radiation than it emits, and vice versa

• the earths temperature depends on things like absorption of IR radiation from the sun, and the emission of radiation from the earths surface and atmosphere

• if an object absorbs and emits the same amount of energy, it remains the same temperature because it is gaining and losing the same amount of heat

• intensity - how much energy the radiation transfers to a given area in a set amount of time

• as the temperature increases:

  • the intensity of every emitted wavelength increases

  • the intensity of shorter wavelengths increases

• for objects at room temperature, the emitted radiation is all in the IR range, rather than visible light, like the Sun

• during the day, the earth absorbs more IR than it emits, so it’s local temperature increases

• during the night, the earth absorbs less IR than it emits, so it’s local temperature decreases

• overall, some part of the earth is always in the sun, so the overall temperature remains constant

2.4 specific heat capacity (shc)

• the temperature of an object rises depending on:

  • amount of energy supplied to it

  • mass

  • what the substance is

• specific heat capacity is how much heat energy in Joules is required to raise the temperature of 1kg of a substance by 1 degree Celsius

• the greater the mass, the slower it increases in temperature

• high SHC - more energy required

• heat - energy required for the temperature to rise in Joules

• temperature - measuring kinetic energy of the particles in degrees Celsius

• storage heaters use electricity at night to heat special bricks/concrete through energy transfer, as bricks have a high SHC so they store lots of energy, and heat up and cool down slowly

2.5 heating and insulating buildings

LOFT INSULATION

• eg. fibreglass

• reduces energy transfer rate in roof

• more insulation layers, thicker insulation, keeps it more warm

CAVITY WALL INSULATION

• reduces energy transfer rate

• traps air in small air pockets

• made of foam

• insulation material used to fill the cavity between the two brick layers of an external house wall

DOUBLE GLAZED WINDOWS

• 2 glass panes with dry air/a vacuum between the panes

• dry air is a good insulator

• thick glass slows the rate of transfer of energy

EXTERNAL WALL

• thicker bricks means less heat will escape from the home

• lowers electrical costs

SOLAR PANELS

• absorb infrared radiation from the sun

• generates electricity directly

also helpful - close fitting door and carpets on floor with rubber underlay

chapter 6 - molecules and matter

6.1 density

• density is the mass per unit volume

• volume of a sphere = 4 x pi x radius³ / 3

• objects with a lower density than water (<100kg/m³) will float in water

6.2 states of matter

solid to liquid - melting

liquid to solid - freezing

gas to liquid - condensation

liquid to gas - vaporisation / boiling

solid to gas - sublimation

6.3 changes of state

• temperature stays the same when changing state

• energy transferred to a substance when it changes state is called latent heat

• energy is needed to melt a solid or boil a liquid

• the flat section of a temp-time graph shows the melting/boiling point of a substance

6.4 internal energy

• energy stored by the particles of a substance is called the substances INTERNAL ENERGY

• internal energy is the sum of:

  • kinetic energy they have due to their individual motions, relative to eachother

  • potential energy they have due to their individual positions relative to each other

• therefore the internal energy of a substance is:

  • the total energy in the kinetic and potential energy stores of the particles in the substance that is caused by their individual motions and positions

• increase temp, increase internal energy

• the pressure of a gas on a surface is caused by the particles of the gas repeatedly hitting the surface

6.5 specific latent heat (slh)

SLH OF VAPORISATION OR FUSION IS THE ENERGY NEEDED TO MELT OR BOIL 1KG OF A SUBSTANCE WITHOUT CHANGING IT’S TEMPERATURE

fusion - solid to liquid

vaporisation - liquid to gas

6.6 gas pressure and temperature

• increasing the temperature of any sealed gas container increases the pressure of the gas inside it

• pressure is proportional to temperature

6.7 gas pressure and volume

when a gas is:

• COMPRESSED, it decreases in volume and increases in pressure

• EXPANDED, it increases in volume and decreases in pressure

for a fixed mass of gas, the no. of gas molecules is constant

if the temperature is constant, the average speed of the molecules is constant

pressure and volume are inversely proportional, so when the pressure increases, the volume decreases, and vice versa

BOYLES LAW

• for a fixed mass of a gas held at constant temperature,

  • pV = constant

  • P1V1 = P2V2

P = pressure, Pascals (Pa)

V = volume, metres cubed (m³)