Energy - Absorbed or Released

When you bake a cake, energy is absorbed by the batter as it changes form a runny mix into a cake.






Another sign of a chemical change is the release or gain of energy by an object. Many substances absorb energy to undergo a chemical change. Energy is absorbed during chemical changes involved in cooking, like baking a cake




Energy can also be released during a chemical change. The fireworks that were mentioned above release energy in a form of light that you can see.



You can also see that energy is released when in this movie clip when sodium and chlorine are combined with water.

Signs of Chemical Changes

How can you tell whether a change is a chemical change?

If you think you are unfamiliar with chemical changes, think again.

A common physical change occurs when matter changes from one phase to another. When an ice cube melts for example, it becomes liquid water. The solid ice and liquid water have the same composition. The only difference is the form.

Color Changes

As in the case of autumn leaves, a change in color is a clue to indicate a chemical change.

Perhaps you have found a half eaten apple that turns brown. The reason is that a chemical change has occurs when food spoils.

You have just witnessed a spectacular chemical change if you have seen the leaves change color in the autumn.

Physical Changes

are relatively easy to identify. If only the form of a substance changes, you have observed a physical change.


A common physical change occurs when matter changes from one phase to another. When an ice cube melts for example, it becomes liquid water. The solid ice and liquid water have the same composition. The only difference is the form.

Chemical Changes

It's the Fourth of July in Providence, Rhode Island. Brilliant fireworks are exploding in the night sky. When you look at the fireworks, you see dazzling sparkles of red, white and blue trickle down in all directions.

The explosion of fireworks is an example of chemical change.

During a chemical change, substances are changed into different substances. Another words, the composition of the substance changes.

Positron

A positron is the same as an electron except it has a positive charge. It is the antimatter equivalent of the electron.

Positrons are released during the nuclear fusion in stars.

Electron

Electrons are tiny particles which behave like clouds. We think of them as clouds of probability. The thickness of the cloud decides how likely it is that you will find the electron at that point.

Electrons carry something called a negative electric charge.

Electrons are important because, together with protons and neutrons, they make the atoms from which you and I are made.

Electrons feel the electromagnetic, weak, and gravitational forces but not the strong nuclear force.

The electron has an antimatter particle called the positron. This has the same mass but carries a positive charge. If it meets an electron, both are annihilated in a burst of radiation.

To get an idea of the size of electrons, visit Soccearth.

Particles

Particles are made from fields. For each particle found in the Universe today there is a corresponding field: for example an electron field. Usually we do not see the fields, only the particles they produce. This association between particles and fields is called the Standard Model of physics. It is the ripples in the field which carry energy and momentum from place to place, generating the things we call particles. A particle can also be called a quantum, meaning "how much". This name came from the discovery that the amount of energy which an electron had when it forms part of an atom cannot vary freely. Its energy can only jump between discrete levels. We say the energy is quantized, or measured. Hence the name quantum. The study of particles and their fields is often called quantum physics. As well as the electron, other particles we meet in this story are the proton and neutron, which in turn are made of smaller particles called quarks. Then there are neutrinos and muons. The standard model has no way to directly explain the mass of particles, so physicists postulate a series of particles, the Higgs particles, which create scalar fields.