Libby Science Revision 2012

Moving things have kinetic energy. The havier a thing is and the faster it moves the more kinetic enegy it has. All moving things have kinetic enrgy, even very large things, like planets, and very small ones, like atoms.

A vibrating drum and a plucked guitar string transfer energy to the air as sound. Kinetic energy from the moving air molecules transfers the sound energy to your eardrum.

Thermal energy is waht we call energy that comes from heat. A cup of hot tea has thermal energy in the form of kinetic energy from its particles. Some of this enrgy is transferred to the particles in cold milk, which you pour in to make the tea cooler.

Some chemical reactions release enrgy. For example, when an explosive goes off, chemical energy stored in it is transferred to the surrondings thermal energy, sound energy and kinetic energy. 

A rock on a mountain has stored energy because of its position above the ground and the pull of gravity. This energy is called gravitational potential energy. This is the energy it would release if it fell. As the rock falls to the ground, the gravitational potential energy is transferred as kinetic energy.                  

A river carries, or transports, pieces of broken rock as it flows along. When the river reaches a lake or the sea, its load of transported rocks settles to the bottom. We say that the rocks are deposited. The deposited rocks build up in layers, called sediments. This process is called sedimentation. The weight of the sediments on top squashes the sediments at the bottom. This is called compaction. The water is squeezed out from between the pieces of rock and crystals of different salts form.

Formation

The inside of the Earth is very hot - hot enough to melt rocks. Molten (liquid) rock forms when rocks melt. The molten rock is called magma. When the magma cools and solidifies, a type of rock called igneous rock forms.                  

What are they like?

Igneous rocks contain randomly arranged interlocking crystals. The size of the crystals depends on how quickly the molten magma solidified. The more slowly the magma cools, the bigger the crystals.

Formation

Earth movements can cause rocks to be deeply buried or squeezed. As a result, the rocks are heated and put under great pressure. They do not melt, but the minerals they contain are changed chemically, forming metamorphic rocks.

Sometimes, metamorphic rocks are formed when rocks are close to some molten magma, and so get heated up. Remember that metamorphic rocks are not made from melting rock. (Rocks that do melt form igneous rocks instead.)                  

Rocks gradually wear away. This is called weathering. There are three types of weathering:

• physical weathering

• chemical weathering

• biological weathering

Remember, when you answer questions about weathering, mention what is causing the weathering and what it does to the rock.

Physical weathering is caused by physical changes such as changes in temperature, freezing and thawing, and the effects of wind, rain and waves.

Temperature changes

When a rock gets hot it expands a little, and when a rock gets cold it contracts a little. If a rock is heated and cooled many times, cracks form and pieces of rock fall away. This type of physical weathering happens a lot in deserts, because it is very hot during the day but very cold at night.