http://www.ck12.org Chapter 2. Matter and Change
2.3 Changes in Matter
Lesson Objectives
- Describe methods for separating mixtures, such as chromatography, distillation, fractional distillation, evapo-
ration, and filtration. - Given a specific mixture, propose methods by which the mixture’s components could be isolated.
- Identify the chemical properties of a substance.
- Describe chemical changes and differentiate them from physical changes.
- Use various visual clues to identify whether a chemical reaction is taking place.
Lesson Vocabulary
- chemical change: A change during which the chemical identity of a substance is altered. Chemical changes
are often accompanied by a change in color, temperature, or odor, or the production of a gas or precipitate. - physical change: A change in which the physical form and properties of a substance change.
- chromatography: The separation of a mixture by passing it through a medium in which the components move
at different rates. - distillation: A purification process in which the components of a liquid mixture are vaporized and then
condensed and isolated. - evaporation: A technique used to separate out homogeneous mixtures in which one or more solids are
dissolved in a liquid. - filtration: A method used to separate mixtures in which some of the particles are large enough in size to be
captured with a porous material while others are not. - chemical property: The ability of a substance to undergo a specific chemical change.
Check Your Understanding
- Compare and contrast chemical properties and physical properties.
- Give examples of physical properties and chemical properties.
- Compare and contrast the following pairs of terms: element and compound; pure substance and mixture.
Introduction
In the previous lesson, we discussed pure substances and mixtures. We indicated that the components of a mixture
could be separated by physical means, but the components of a pure substance could not. Pure substances can only
be broken down further through chemical means. In this lesson, we list several methods for separating mixtures. We
will also be looking atchemical changeswhich alter the chemical identity of a substance, and how to recognize
when a chemical change is taking place.