Simple Physics Revision on Heat and Temperature <3

Physics Revision <3

Heat and Temperature

Heat and temperature DO NOT mean the same thing. Heat is a form of energy and so it is measured in joules (J). Temperature is measured of how hot or cold something is. It is measured in Degrees Celsius. A thermometer is used to measure temperature. When heat energy is supplied to a substance, its temperature increases. Heat temperature also flows from places of high temp to places of low temp.

There are three ways heat can travel conduction, convection and radiation.

Conduction

This is when heat flows through some solids. Heated particles vibrate faster and bump into there neighbours. This passes the heat energy along from  to particle.

Conductors and Insulators

Substances which are good at passing heat this way are called conductors. These are mainly metals. Substances which are not good at passing heat this way are called Insulators. These are mainly non-metals. You can touch to oblects which are at the same temp but one feels colder to the touch. This because one object is a better conductor andd it is conducting the heat away from your body. This makes your obdy feel cooler and you think that the object is colder.

Convection

Water and air are poor conductors of heat. This is because it is difficult for the heat energy to be passed on by vibrating particles. The particles in a liquid are not evenly spaced and the particles in  a gas are too far apart for the vibrations to be past on. The main way heat travels in liquids and gases is by convection. Heated liquids and gases become less dense and so rise upwards. As a result, a flow pattern is a set up in the fluid. This is called a convection current.

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Radiation

Another name for radiation heat is infrared radiation. It is invisible, but our skin can feel it, for example on a hot sunny day. Radiated heat does not need a substance to carry it. It can travel through empty spaces (a vacuum). A substance which is hotter than it surroundings gives out more radiated heat then it absorbs. Black and dull surfaces are better at losing heat by radiation the surfaces which are light and shiny.

Energy efficient homes

(only main points)

Roofs: Loft Insulation
Trap air in fibers
helps stop heat loss

Windows: Double or triple glazing
layers of glass act as insulators
Another way of cutting heat loss is to fit thick and heavy curtains and close them at night

Draughts: Simple draught excluders

Sealant to fill in some bigger gaps