Flashcards in everything Deck (68)
What is infrared radiation?
Infrared radiation is energy transfer by magnetic waves.
Do all objects give off infrared radiation?
All objects emit infrared radiation.
How does infrared radiation depend on the temperature of an object?
The hotter an object is, the more infrared radiation it emits over a given time.
Which surfaces are the best emitters of infrared radiation?
Dark Matt surfaces emit more infrared radiation than light, shiny surfaces.
Which surfaces are the best absorbers of infared radiation?
Dark, Matt surfaces absorb more infrared radiation that light shiny surfaces.
What surfaces are the best reflectors of infrared radiation?
Light, shiny surfaces reflect more infrared radiation than dark Matt surfaces.
How are solids, liquids and gases different?
Flow, shape and density are the properties used to describe each state of matter.
How are particles in a solid arranged and describe it's shape?
The particles in a solid are held in fixed positions and they vibrate their fixed positions so that the solid keeps it's shape. the particles in a gas move about randomly and are much further apart than in a solid or a liquid.
What materials make the best conductors?
Metals are the best conductors of energy because they contain free electrons.
What materials make the best insulators?
Materials such as wood and plastic ( in general non metals )
What are the three states of matter?
Solid, liquids and gases.
What happens to the particles when the temperate of a substance increases?
The particles move faster.
How are the particles arranged in a liquid and describe it's shape?
the particles in a liquid move about at random and are in contact with each other, because they move about at random they don't have their own shape and it can flow.
How are the particles in a gas arranged and describe it's shape?
The particles in a gas move about at random much faster and on average much further apart from eachother than in a liquid. The density of a gas is thus much less than that of a solid or a liquid.
In general what is the energy levels in: solids, liquids gases.
Gas < liquid
Liquid < solid
Why do metals make such good conductors?
Metals contain lots of free electrons which move about at random inside the metal and collide with eachother and with the positive ions ( ions are charged particles) When a metal did is heated at one end the free electrons at the hot end gain kinetic energy and move faster.
These electrons diffuse ( spread out ) and collide with other free electrons and ions in the cooler parts of the metal, as a result they transfer kinetic energy to these electrons and ions. So energy is transferred from the hotter end to the cooler end.
Why are non metals bad conductors compared with metals?
In non metals all the electrons are held in the atoms and energy transfer only games place because the atoms vibrate and shake eachother. This is much less effective than energy transfer by free electrons thus making them worse conductors.
What is convection and why does it happen?
Convection is the circulation of a fluid ( liquid of gas ) cauSed by heating it.
Heating a liquid or a gas makes it less sense so it then rises and then when t cools down it falls (because when it cools it becomes more dense ). Causing a convection current from the hotter parts to the cooler parts.
What is evaporation?
Evaporation is when a liquid turns into a gas.
What is condensation?
Condensation is when a gas turns into a liquid.
How can the rate at which evaporation occurs be increased?
- increasing the surface area of the liquid
- increasing the liquids temperature
- creating a draught of air across the liquids surface
What factors increase the rate at which condensation occurs?
- increasing the area of the surface
- reducing the temperature of the surface.
What affects the rate at which an object transfers energy?
The surface area and volume
What the objects made from
The nature of the surface which the object is in contact with
How can the rate at which energy is transferred be increased?
The bigger the temperature difference between an object and it's surroundings the faster the rate at which energy is transferred by heating.
What does U-values measure?
How affective of an insulator a material is because it tells us how much energy per second passes through different materials.
What does a low U-value tell us?
That it is a better insulator than a higher U-value.
What is the specific heat capacity of a substance?
The amount of energy required to change the temperature of one migrants of the substance by 1 degrees Celsius.
What does the term ' pay back time ' mean?
The amount of time it takes to get back your investment.
why is knowing the efficiency of an appliance important?
So that we can choose between then and get the most cost affective.