Physical and Chemical Changes

Physical change is a change that alters the form or appearance of a material without changing the chemical composition. One example of a physical change is dissolving. Salt is made of ions that are ionically bonded together in a crystal. Sugar is made of molecules that are bonded together based on the positively and negatively charged areas.

Physical change is a change that alters the form or appearance of a material without changing the chemical composition. One example of a physical change is dissolving. Salt is made of ions that are ionically bonded together in a crystal. Sugar is made of molecules that are bonded together based on the positively and negatively charged areas.

Solids, liquids, and gases can all dissolve. Dissolving depends on the molecules of the substance doing the dissolving, called the solvent, and the molecules of the substance being dissolved, called the solute. Dissolving is the process in which these molecules interact and attract each other to form a solution.

Matter exists in three states or phases: solid, liquid, and gas. A combination of the motion of molecules and their attraction for one another determines whether a substance is a solid, liquid, or gas. Adding heat energy increases the motion of molecules. Removing heat energy, or cooling, decreases the motion of molecules.

A chemical reaction happens when one or more substances change into entirely new substances with different properties. The clues of a chemical reaction are production of a gas, change in temperature, color change, production of a precipitate. In a chemical reaction, it takes energy to break the bonds in the reactants and energy is released when bonds are formed in the products.

Helpful chemistry videos related to physical/chemical changes, states of matter, balancing chemical equations, and the Law of Conservation of Matter

Matter is everything around you. Atoms and molecules are all composed of matter. Matter is anything that has mass and takes up space.

Click on the links to the right for more information on mixtures, physical changes, chemical changes, phase changes, and more.

Teacher background about Chapter 1 from Middle School Chemistry, a collection of free inquiry based lesson plans from the American Chemical Society. http://www.middleschoolchemistry.com/lessonplans/chapter1

Explore the five states of matter: solid, liquid, gas, plasma, and Bose-Einstein condensates

In cooperation with the National Science Foundation, NBC Learn explores presence and function of chemistry in everyday life and in world around us. There are a lot of videos here to explain the chemistry in everything from cheeseburgers and plastic to kevlar and why leaves change color.

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Learn how to balance chemical equations by changing the number of coefficients.

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Heat, cool and compress atoms and molecules and watch as they change between solid, liquid and gas phases.