Density is also an important physical property of matter. The concept of density combines what we know about an objects mass and volume. Density reflects how closely packed the particles of matter are. When particles are packed together more tightly, matter is more dense. Differences in density of matter explain many phenomena. It explains why helium balloons rise. It explains why currents such as the Gulf Stream flow through the oceans. It explains why some things float in or sink. You can see this in action by pouring vegetable oil into water. You can see a colorful demonstration in this video.

Based on the explanation in the article, why do you expect to happen with the water and oil?

Above were just a few things that caused habitat loss or change. There are many ways in which living organisms can affect their ecosystem. In some areas, it is because of fire management. Fire is a natural event, so managing fire correctly is very important. In other areas, fisherman have taken too many fish from one area. This places the species at risk of extinction. It also affects other living things that may rely on these fish for food. The image below shows a picture of a mine. Mining changes the Earths surface. This area may once have been a forest or a prairie. Think about how many plants and animals may once have lived here. Now it is a giant hole in the ground. Pollution is also a major factor in habitat loss and change.

What can occur if fishermen over-fish an area?

The center of an atom is held together by powerful forces. This gives them a huge amount of stored energy. This type of energy is called nuclear energy. This energy can be released and used to do work. This happens in nuclear power plants where they split apart the nucleus of an atom. This splitting apart is called nuclear fission. Another type of nuclear energy happens in the Sun. Here the atoms nuclei are not split apart. Instead, the nuclei of the atoms are fused, or joined together. This process is called nuclear fusion. Some of the suns energy travels to Earth. This energy from nuclear fusion warms the planet and provides the energy for photosynthesis.
Some of the Sun's energy travels to Earth and becomes energy for what process?