Properties of Matter 17 2 Objectives Identify substances

Properties of Matter 17 -2

Objectives Identify substances using physical properties l Differentiate between physical and chemical properties and changes. l Determine how the law of conservation of mass applies to chemical changes. l l l CLE 3202. 1. 1 Explore matter in terms of its physical and chemical properties. CLE 3202. 1. 4 Investigate chemical and physical changes.

A. Physical Properties Characteristics that can be observed without changing the substance 1. Examples include: color, shape, size, and density

Physical Properties 2. 3. Appearance – physical description of a substance Behavior - how a substance acts; for example: magnetism, viscosity, ductile (drawn into a thin wire) vs brittle

Physical Properties 4. Some of these properties can be measured such as the height, width, melting point, and boiling point and freezing point

2 Properties of Matter Appearance • How would you describe a tennis ball? You could begin by describing its shape, color, and state of matter. • You can measure some physical properties, too. For instance, you could measure the diameter of the ball.

Physical Properties 5. Physical properties such as size and magnetism can be used to separate mixtures. Attraction to a magnet is a physical property of the substance iron. The magnet attracts only the iron filings and pulls them from the sand.

6. Every substance has physical properties that make it unique.

B. Physical Changes in a substance’s size shape or state of matter. 1. Substance does not change identity when it undergoes a physical change.

Properties of Matter 2 The Identity Remains the Same • Iron is a substance that can change states if it absorbs or releases enough energy—at high temperatures, it melts. • Color changes can accompany a physical change, too. • For example, when iron is heated it first glows red. Then, if it is heated to a higher temperature, it turns white.

Physical Changes 2. 3. Energy changes occur during these changes in state, but the kind of substance does NOT change. Examples: boiling, freezing evaporating - the state of matter changes but NOT the chemical makeup.

Distillation is a process for separating a mixture by evaporating a liquid and condensing its vapor. l Many such areas that lie close to the sea obtain drinking water by the use of distillation to separate water from the salt. l

Distillation Apparatus

Phase Changes are Physical Changes l Condensation gas to liquid l Evaporation liquid to gas l Freezing liquid to solid l Melting solid to liquid l Sublimation solid to gas

C. Chemical Properties characteristics of a substance indicating that it can change chemically for example: flammable, combustible, or light sensitivity of a substance.

D. Chemical Change When one substance changes to another substance, a chemical change has occurred. 1. Some chemical changes are indicated by temperature change, smell, or bubble formation, foaming, burning and color change.

2. Other chemical changes occur very slowly such as the formation of rust or tarnish on silver. 3. Chemical changes can be used to separate substances such as metals from their ores.

SILVER NITRATE & COPPER

AFTER THE REACTION

COPPER SULFATE & Fe

AFTER THE REACTION

Alka-seltzer in water

E. Weathering of Earth’s surface involves both physical and chemical changes.

Weathering 1. 2. Physical - big rocks split into smaller ones; streams carry rock particles from one location to another Chemical - chemical changes can occur in rocks and monuments when calcium carbonate in limestone changes to calcium hydrogen carbonate due to acid rain.

Statue of George Washington in NYC Acid rain damage over 50 yrs U. S. Grant memorial in D. C. (bronze)

Above Ground Cemetery in New Orleans Note that the urn and tops of ledges are heavily weathered, but the inscriptions are somewhat sheltered and remain legible.

Damage to Statue by Acid Rain

Acid Rain Compounds from burning coal, oil and gas react chemically with water forming acids. n Acid rain causes very rapid chemical weathering n

F. Law of Conservation of Mass of all substances present before a chemical change equals the mass of all substances after the change.

Cont. During Chemical Changes, matter and energy cannot be created nor destroyed. The substance just changes form.

Properties of Matter 2 The Conservation of Mass • Suppose you burn a large log until nothing is left but a small pile of ashes. • At first, you might think that matter was lost during this change because the pile of ashes looks much smaller than the log did.

Properties of Matter 2 The Conservation of Mass • In fact, the mass of the ashes is less than that of the log.

Properties of Matter 2 The Conservation of Mass • However, suppose that you could collect all the oxygen in the air that was combined with the log during the burning and all the smoke and gases that escaped from the burning log and measure their masses, too. • Then you would find that no mass was lost after all.

Properties of Matter 2 The Conservation of Mass • Not only is no mass lost during burning, mass is not gained or lost during any chemical change. • According to the law of conservation of mass, the mass of all substances that are present before a chemical change equals the mass of all the substances that remain after the change.

Question: Is distillation a physical or chemical change? Explain.

Answer Physical change because identities of substances do not change.

Section Check 2 Question 2 Which of the following is a chemical property? A. boiling point B. density C. flammability D. melting point

Section Check 2 Answer The answer is C. Flammability indicates whether a substance will undergo the chemical change of burning.

Section Check 2 Question 3 A characteristic of a material that can be observed without changing the identity of the substances that make up the material is a _______.

Section Check 2 Answer The answer is physical property. Examples of physical properties include color, shape, and density.

Section Check 2 Question 4 What is the law of conservation of mass?

Section Check 2 Answer According to the law of conservation of mass, the mass of all substances that are present before a chemical change equals the mass of all substances that remain after the change.

Objectives Identify substances using physical properties l Differentiate between physical and chemical properties and changes. l Determine how the law of conservation of mass applies to chemical changes. l l l CLE 3202. 1. 1 Explore matter in terms of its physical and chemical properties. CLE 3202. 1. 4 Investigate chemical and physical changes.