P2.1 - Conduction. Flashcards
(13 cards)
Describe the method for a practical investigating different conductivities of different materials
gather equipment
[] 5 identical glass beakers (300ml)
[] kettle
[] lids for each beaker with a hole for the thermometer
[] thermometer
[] timer
[] 4 different materials (newspaper, bubble wrap, foam, cloth) - ALL SHOULD BE OF THE SAME MASS
-wrap each material around one beaker, leaving one uncovered
[] make sure to cover the bottoms of the beakers as well to reduce conduction to the work surface
in one beaker,
-pour 250cm^3 of just-boiled water and quickly put the lid with thermometer on
[] the bulb of the thermometer must be in the water
-wait for the water to reach a maximum temperature, then begin the timer
-record the start temperature of the first beaker
check and record the temperature every three minutes over 15 minutes total
-repeat with the other 4 beakers
-plot cooling curves for each beaker and label which had which material
Describe the method to investigate the relationship between the thickness of the thermal insulator used and loss of heat
A
gather equipment
[] 5 identical beakers (300ml)
[] bubblewrap or newspaper
[] timer
[] lid for each beaker with a hole for thermometer
[] thermometer
[] kettle + water
prepare each beaker
[] one w/no bubblewrap
[] one w/two layers
[] one w/four layers
[] one w/six layers
[] one w/eight layers
[] MAKE SURE TO COVER BOTTOMS AS WELL
-pour 250cm^3 of just-boiled water in one flask and cover with lid and thermometer, making sure the bulb is inside the water
-wait for it to reach a maximum temperature before starting the timer
-start the timer and record the start temperature of the water
-measure and record the temperature every three minutes over 15 minutes total
-repeat with the other four beakers
-plot cooling curves for each beaker on a graph with temperature on the y-axis and time on the x-axis
What is thermal conductivity ?
How well a material conducts (transfers) thermal energy
What does the quality of insulation of a material depend on ?
thermal conductivity
thickness/no. of layers of the material used
temp. difference across the material
What absorbs/emits infrared radiation ?
everything
How does temperature affect emission of infrared radiation ?
higher temp = more emission, whilst lower temp = less emission
What colour/surface is the best at both emitting and absorbing infrared radiation ?
matte black
What is black body radiation ?
infrared radiation emitted from a perfect black body (perfect black bodies are the best possible emitters and absorbers of infrared)
What does the Earth’s temperature depend on ?
rate of absorption and emission of infrared radiation from the sun into Earth/the atmosphere/space
What is a perfect black body ?
an object that is the best possible absorber and emitter of radiation
- ABSORBS ALL INCIDENT RADIATION
How does the temperature of an object increase/decrease ?
absorbing/emitting more infrared radiation than it emits/absorbs
What is the relationship between an object’s temperature and the range of wavelengths of radiation it emits ?
An object with a constant temperature emits radiation across a continuous range of wavelengths
how to reduce energy transfer in any given situation:
- thermal conductivity of the insulating material should be as low as possible
- thickess of the insulatinglayer should be as tjick as practically possible
