703562
Description
Flashcards by x_clairey_x, updated more than 1 year ago
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Created by x_clairey_x
over 11 years ago
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| Question | Answer |
| Which objects absorb and emit infrared radiation? | All objects emit and absorb infrared radiation |
| what makes an object radiate more infrared radiation? | How hot it is, the hotter the object the more infrared radiation it radiates |
| What type of surface is perfect for emitting and absorbing infrared radiation? | Dark, matt surfaces are good at absorbing and emitting infrared radiation. |
| what makes a bad surface for emitting and absorbing infrared radiation? | Light, shiny surfaces are bad at emitting and absorbing infrared radiation. |
| What sort of surface would be good at reflecting infrared radiation? | Light, shiny surfaces |
| What does a fluid do when heated? | Expands, becomes less dense, rises and causes circulation (convection) |
| Infrared radiation is transfer of energy by what type of wave? | Electromagnetic waves |
| What are all materials made out of? | particles |
| What are the best conductors of energy? | Metals |
| What materials are the best insulators? | Wool and fibreglass |
| How does conduction take place? | free electrons transfer energy inside metals |
| Why are non metals not good at conducting? | They don't have free electrons |
| What is convection? | The circulation of a fluid (liquid or gas) caused by heating it |
| What is evaporation? | When a liquid turns into a gas |
| What is condensation? | When a gas tuns into a liquid |
| How does evaporation cause cooling? | The faster moving-molecules escape from the liquid |
| How can evaporation be increased? | -Increase the surface area of the liquid -Increase the temperature of the liquid -Create a draught of air across the liquid's surface |
| How can condensation on a surface be increased? | -Increase the area of the surface -Reduce the temperature of the surface |
| What does the rate of energy transfer to or from an object depend on? | -The size, shape and type of material of the object -The materials the object is in contact with -The temperature difference between the object and its surroundings |
| How will the mass of an object change how quickly the temperature changes when heated? | The greater the mass, the slower the temperature increases. |
| What does the rate of a substance's temperature change depend on when it is heated? | -The energy supplied to it -Its mass -Its specific heat capacity |
| What is specific heat capacity? | The energy required to raise 1kg of a substance by 1 degree Celsius |
| How do you work out specific heat capacity? | c= E ------- m x (theta) E=Energy transferred (J) m=Mass (kg) c= Specific head capacity (j/kg oC) theta=temperature change (oC) |
| How can energy transfer be reduced in our homes? | -Loft insulation -Cavity wall insulation -Double Glazing -Draught excluders -Aluminium foil behind radiators |
| What does a U-Value tell us? | How much energy per second travels through a material. |
| What does a low U-Value mean? | The material is a good insulator |
| What does a high U-Value mean? | The material is bad at insulating |
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