Matter and changes in matter

MATTER AND CHANGES IN MATTER

Matter and Changes in Matter

Matter is anything that has mass and volume, including all solids, liquids, and gases. To understand changes in matter, you need to know that the sample of matter was like before the change and what it is like after the change. You also need to be able to describe and classify atter. There are many ways in which matter could be classified, but s.:ientists have found it useful to classify matter according to its properties, or characteristics. Properties are ways of describing things so that we can identify them. Any kind of matter can be classified as a mixture or a pure substance.

Physical and Chemical changes

When matter changes, what happens to it? After some changes, mat­ter may still have the same properties. When you tear paper into small pieces, for example, each piece still has the properties of the original paper. When a balloon bursts, the rubber is still the same color and is still just as soft and stretchy as it was in the balloon. When ice melts, the water is still the same substance-it can easily be arranged back into ice if it is cooled. These are physical changes, changes in which no new substance is produced.

During some changes, a new substance may appear. For example, if you leavve your bicycle out in the rain, a reddish-brown crumbly substance may form on it. This substance-rust-is quite different from the shiny, hard etal that was used to make the new bicycle. Changes such as this, in which new substances are produced, are called chemical changes. If one or more new substances are produced-substance(s) with prop­erties that are different from the properties of the starting material(s) then a chemical change has occurred. Chemical changes may involve energy; heat or light may be given off during the change. Most chemical changes, cannot be easily reversed.

Differentiating between physical and chemical change

It is not always easy to tell the difference between a physical change and a chemical change. Some chemical changes may pro­duce flames, sparks, and noise, but many do not. The chemical changes that take place when you bake a cake, polish brass, or clean the oven are much less spectacular. However, cer­tain clues may tell you that a chemical change has occurred:

• A new color may appear. 
• Heat or light may be given off. 
• Bubbles of gas may be formed. 
• Solid material may form in a liquid. 
• The change may be difficult to reverse. 

Any of these clues could also be part of a physical change. You need to consider several clues in order to determine which type of change has taken place.

Posted in Chemistry , Physics