PHYSICAL AND CHEMICAL CHANGES

PHYSICAL CHANGE PHYSICAL CHANGE When the appearance or form of a substance is changed but no new substance is produced.

PHYSICAL CHANGES As you know, matter occurs in three states – solid, liquid, and gas. A puddle of liquid water left in the sun will not be there in two hours. The water won’t disappear but a physical change will happen. The liquid water changes into water vapor, a gas. When the appearance or form of a substance has changed but no new substance is produced, the matter has undergone a physical change. All changes in the state of matter of a substance are physical changes. Other examples of physical changes are bending, crushing, breaking, and dissolving. The methods of separating mixtures, such as filtration and distillation, also involve physical changes.

PHYSICAL CHANGES Changes in the state of matter of a substance are physical changes.

OTHER PHYSICAL CHANGES BENDING

OTHER PHYSICAL CHANGES Crushing

OTHER PHYSICAL CHANGES Breaking

OTHER PHYSICAL CHANGES Dissolving

CHEMICAL CHANGE A change in matter that produces one or more new substances is called a chemical change or chemical reaction.

CHEMICAL CHANGE A change in matter that produces one or more new substances is a chemical change, or chemical reaction. In some chemical changes, a substance breaks down into two or more other substances. For example, hydrogen peroxide breaks down into water and oxygen gas when it’s poured on a cut on your skin. In other chemical changes, two or more substances combine to form different substances.

CHEMICAL CHANGE PHOTOSYNTHESIS Everything you encounter is made up of some combination of a finite set of elements. Atoms from two or more of these elements can combine in many ways. Photosynthesis is a chemical change that happens naturally in plants. Several compounds combine using energy from the sun to produce new compounds. All living and nonliving things are made up of substances that formed through a wide variety of chemical changes of the elements.

EXAMPLES OF CHEMICAL CHANGES COMBUSTION – the rapid combination of a fuel with oxygen. Combustion produces heat, light, and new substances Example: gas, oil, or coal burning in a furnace.

EXAMPLES OF CHEMICAL CHANGES Electrolysis – the use of electricity to break a compound into elements or simpler compounds Example – the use of electricity to break water down into hydrogen and oxygen.

EXAMPLES OF CHEMICAL CHANGES Oxidation – the combination of a substance with oxygen. Example – the rusting of iron

How do I know if a change is chemical or physical? There are clues we can use to let us know if a chemical change has taken place……

#1 Change of color Chemical changes often involve a change of color

#2 Change in Temperature Chemical reactions often give off or absorb heat.

#3 Changing Form Chemical reactions often involve a change in the form of the material.

#4 Release of light, heat, or sound

#5 Formation of gases Chemical reactions often involve the release of gases (bubbles)

#6 Form of precipitate Chemical reactions often involve the formation of a precipitate.

#7 Decomposition of Organic Matter The decomposition of organic matter is a chemical reaction