P2- Year 9 Flashcards
What does a materials thermal conductivity tell you?
How well it allows heat to pass through it
Which materials have a low thermal conductivity?
Wool, water, foam, wood, fibreglass (non-metals)
What 3 factors affect the rate of energy transfer through a marterial per second?
Thickness, thermal conductivity, temperature difference
What 2 factors affect the rate of heat loss from a building?
Temperature difference
Amount of insulation
Define specific heat capacity
The amount of energy needed to change the temperature of 1kg of substance by 1 degree Celsius
What does temperature change depend on?
The amount of kinetic energy particles have
What is infrared radiation a part of?
The electromagnetic spectrum
What does emit mean?
Give out
What does absorb mean?
Take in
What does it mean for an object that is at a constant temperature?
When an object emits and absorbs radiation at the same rate, it is at an equilibrium
How does an objects temperature increase?
When an object absorbs more thermal energy than it emits
What is a black body?
A theoretical object that absorbs all the
radiation that hits it
Name 3 greenhouse gases
Carbon dioxide
Methane
Nitrous oxide
How does radiation from the sun affect the temperature of the Earth?
The Earth absorbs infrared radiation from the Sun, increasingly the temperature on Earth
What human activities increase the Earth’s temperature?
Burning fossil fuels
Cutting down trees
Farming
What does an increase in the Earth’s temperature lead to?
Increased global warming and climate change
Why do homes need insulation?
To reduce the amount of heat lost, therefore reducing the cost required to heat the home and the environmental impact
Describe how loft insulation reduces heat loss in houses
Loft insulation is usually fibreglass, which has a low thermal conductivity. It contains gaps of air which reduces the amount of heat loss by conduction as gasses are poor conductors
Describe how double glazing reduces heat loss in houses
Have 2 thick window panes with an air gap in between. Glass has low thermal conductivity and the air prevents heat being lost through conduction
What is meant by ‘payback’ in terms of installing insulation
The amount of time it takes Ames for the amount of money saved to equate to the amount it cost
