Phases of Matter

· Phases of Matter

Matter is the “stuff” we have been talking about for some time now. Everything that takes up space or has mass is made of matter. There are four states or phases of matter that you should be familiar with. They are…

· Solids - definite shape and volume

· Liquids- take the shape of the container, so they have no definite shape. They do have definite volume.

· Gas- No definite shape or volume.

· Plasma-super high energy. Rare on earth. Common in the Sun.

Matter is always in one of these states of matter. Which one depends on how much energy the matter has. A gain or loss in energy can cause the matter to change phases.

Lets see how this happens.

Melting- Phase change from a solid to a liquid. This occurs when enough energy is added to a solid. Even something as solid as rock can melt if enough heat is provided.

Freezing- Phase change from a liquid to a solid. This occurs when energy is taken away from a solid. When molten lava cools down, it turns into solid rock.

Evaporation- Phase change from a liquid to gas. This occurs when energy is added to a liquid. On hot summer days, puddles of water quickly turn into a gas (water vapor) and disappears from sight.

Condensation- Phase change from a gas to a liquid. This occurs when energy is taken away from a gas. The water vapor from the puddle rises high into the air where it gets colder. The vapor starts to condense into little water droplets, which eventually forms a cloud. The water droplets on the outside of your glass is another example of condensation.

Sublimation- Phase change from a solid directly to a gas. When energy is added to some solids, like dry ice, the matter skips the melting phase and goes directly to a gas. This is called sublimation.

Chemical change vs. Physical change

In chemistry, a physical change occurs when a substance changes its size or shape. An example of this would be chopping a log into tiny toothpicks. You start out with a large piece of wood and wind up with many small pieces of wood. You begin and end with wood. Changing phase is also a physical change. When you freeze water, you get ice. Ice is just water, only in a solid state. You have the same thing. It has the same properties.

In chemistry, a chemical change occurs when a substance changes into something entirely new. An example of this would be taking a log and burning it. You start with wood and wind up with ashes. Ashes and wood are different. Another example would be the rusting of a nail. You begin with iron and you get rust. The two are not the same. Iron and rust have different properties. One is hard and smooth, the other is flakey and rough. Getting the idea???

A physical change is a change where

· Types of Matter

Matter can be two things, a pure substance or a mixture.

· Pure substances: these have a fixed composition and set of physical properties.

· Mixtures: two or more pure substances mixed together.

Pure substances can be either elements or compounds. Elements are also known as atoms. Compounds are made up of more than one atom that have been chemically combined. Water is an example.

Pure substances:

· Elements: any matter that cannot be broken down into further pure substances. The elements are listed on the periodic table: we currently know of about 115. Iron and uranium are elements

· Compounds: pure substances made up of one or more elements. Water is a compound: it is made up of two hydrogen atoms and 1 oxygen atom. (H₂O)

Mixtures can be either homogeneous or heterogeneous. They are not chemically combined!

Mixtures:

· Homogeneous: a homogeneous mixture is one that appears the same throughout. It is very well mixed. Sea water is a homogeneous mixture of water, table salt and a variety of other compounds, stainless steel is a homogeneous mixture of iron, carbon, nickel and other elements.

· Heterogeneous: mixtures that are poorly mixed. The substances that are mixed together are easily seen.

Example: A banana split is a heterogeneous mixture of ice cream, bananas, whipped cream, nuts, chocolate syrup and other things. The chocolate syrup is a homogeneous mixture of water, cocoa powder, sugar and other compounds. If you look at the syrup it all looks the same.

The thing to remember about mixtures is that you start with some pieces, combine them, and then you can do something to pull those pieces apart again. You wind up with the same molecules (in the same amounts) that you started with. Compounds, on the other hand, can not be turned back into the original parts. There has been a chemical change.

A mixture is when two or more things are put together. There are two types of mixtures; those containing all the "same stuff" or homogeneous, and the other containing "different stuff" or heterogeneous. Kool-aid is a mixture where all the "parts" are the same and is an example of the homogeneous mixture. Fruit salad as an example of the heterogeneous mixture. So a mixture is when two things are put together but are not chemically combined

A solution is a homogenous mixture where one thing is dissolved into another. A solution is made up of two parts.

Solute- the substance that gets dissolved

Solvent-the substance that does the dissolving.

Some substances, like sand, cannot be dissolved. Such substances are said to be insoluble.

Lemonade is a solution. It looks the same throughout (yellow liquid). It has dissolved sugar (solute) in water and lemon juice (solvent).