Changes in Matter Chapter 2 Section 3

Physical Properties Any such characteristic of a material that you can observe without changing the substance that make up the property is called a Physical Property. Physical properties are used to observe and describe matter.

Physical Properties continued Physical properties include: appearance, texture, color, odor, melting point, boiling point, density, solubility, polarity, and many others. Every substance has physical properties that distinguish it from other substances.

Physical and Chemical Changes. A change in size, shape, or state of matter is called a physical change. Physical changes do not change the identities of the substance in a material. A change of one substance in a material to a different substance is a chemical change.

Chemical Properties A Chemical Property is a characteristic of a substance that indicates whether it can undergo a certain chemical change. Examples of chemical properties are: flammability, combustion, reactivity with water, and pH.

The Conservation of Mass During the 18th century, chemical reactions were still a mystery. A French scientist, Antoine Laurent Lavoisier ( ), established an important principal based on his experiments with chemical reactions. The most significant observation he made was that, even though one substance is transformed into another during a the course of a reaction, the total mass of the products is the same as the total mass of the reactants.

Conservation of Mass continued. Sometimes the products of a chemical reaction look different from the reactants. If a gas is produced, you may not see it. Yet its mass must be taken into account in finding the total mass of the products. The Law of Conservation of Mass is an important law of chemistry. This law holds true for all chemical reactions. French Chemistry students are still taught the conservation of mass as “Lavoisier’s Law” is indicative of his success in making this principle a foundation of modern chemistry.

Conservation of Mass continued. In order to prove the Conservation of Mass in a chemical reaction, a closed system must be used. When chemicals are reacted in a closed container, you can show that the mass before and after the reaction is the same. In one experiment Lavoisier placed 10.0g of mercury oxide into a sealed container. He heated the container so that the mercury oxide reacted to produce oxygen and mercury. As he observed the reaction, the white, powdery mercury oxide bubbled, and turned into a smaller amount of a silvery liquid.

Conservation of Mass continued In the reaction, 10.0 grams of mercury oxide reacted in the presence of heat to produce.7 grams of oxygen and 9.3 grams of mercury. How does this data prove the law of conservation of mass?