Physical & Chemical Properties Physical & Chemical Changes Chapter 3 Physical & Chemical Properties Physical & Chemical Changes

Physical Properties Characteristics of a substance that can be observed without changing the identity of the substance. Examples include: mass, weight, volume, density, color, shape, hardness, & texture

Physical Changes when only the form of a substance changes example = change in phase like solid ice to liquid water

Properties that describe how a substance changes into new substances Chemical Properties Properties that describe how a substance changes into new substances Examples include: flammability, support for burning, and the ease with which it combines with other substances

Chemical Changes During a chemical change, substances are changed into different substances. In other words, the composition of the substance changes.

Chemical changes create new substances that can not be undone. Physical changes do not change the chemical composition of the substance Chemical changes create new substances that can not be undone.

Evidence of a Chemical Change Color change Odor change Energy change Formation of a gas or solid Not easily reversed

Color Changes As in the case of autumn leaves, a change in color is a clue to indicate a chemical change.

Color Changes Perhaps you have found a half eaten apple that turns brown. The reason is that a chemical change has occurred when food spoils.

Odor Changes It only takes one experience with a rotten egg to learn that they smell different that fresh eggs. When eggs & food spoil, they undergo a chemical change.

Energy Absorbed or Released the release or gain of energy by an object indicates a chemical change

Energy is absorbed during chemical changes involved in cooking, like baking a cake

Energy Released Energy can also be released during a chemical change. Fireworks release energy in a form of light that you can see.

Reaction of Sodium With Chlorine Na & Cl Reaction of Sodium With Chlorine You can also see that energy is released when in this movie clip sodium & chlorine are combined with water.

Production of a Solid A solid that separates out of solution during a chemical change is called a precipitate.

Production of a Gas The formation of a gas is a clue to chemical changes. The bubbles of gas that you observed form when an antacid is dropped into water is an example.

Physical = Easily reversed After ice melts into liquid water, you can refreeze it into solid ice if the temperature drops. Freezing & melting are physical changes

Chemical- Not easily reversed The substances produced during chemical changes however cannot easily change back into the original substances like when you burn wood.

Chemical Reactions Chemical Changes are also called Chemical Reactions. Chemical reactions involve combining different substances. The chemical reaction produces a new substance with new & different physical and chemical properties.

Law of Conservation of Mass Matter is never destroyed or created in chemical reactions. The particles of one substance are rearranged to form a new substance. The same # of particles that exist before the reaction exist after the reaction.