Chapter 3 Properties of Matter

What is chemstry? The study of matter and the changes that it undergoes.

What is matter? Anything that has mass and takes of space.

Substances Matter with a uniform and unchanging composition is a pure substance. Examples: Water (pure) – H2O Table Salt – NaCl Tap water and sea water are not pure substances, why not?

Mixtures A mixture is a combination of two or more pure substances in which each pure substance retains its individual chemical properties. Example Fillings are actually a mixture of mercury and silver. Oil and vinegar salad dressing

Two types of mixtures A heterogeneous mixture does not blend smoothly throughout and the individual substances remain distinct. Examples Orange juice with pulp Oil and vinegar salad dressing

A homogeneous mixture has a constant composition. Examples Amalgam fillings Tap water Air Sugar water

Homogeneous mixtures are also called solutions Solutions can be solids, liquids or gases or they can be a combination of any of the three. A solid-solid solution is called an alloy. Examples Steel = iron and carbon Bronze = copper and tin

Gas-gas solution: air in a scuba tank (N, O, Ar) Gas-liquid solution: O2 and CO2 in sea water Liquid-gas solution: H2O in the air we breathe Liquid-Liquid solution: fresh water mixes with sea water Solid-Liquid solution: salts in sea water

States of Matter Solid Liquid Gas Plasma

A solid has its own definite shape and volume. The particles of a solid are tightly packed It will not conform to the container in which it is placed. It cannot be compressed into a smaller volume.

A liquid is a form of matter that flows, has constant volume, and takes the shape of its container.

A gas is a form of matter that flows, conforms to the shape of its container and fills the entire volume of its container. Gases are easily compressed.

Physical Properties of Matter A characteristic that can be observed or measured without changing the samples composition is a physical property. Physical properties also describe pure substances because substances have a uniform and unchanging chemical composition. Substances also have consistent and unchanging physical properties. EXAMPLES OF PHYSICAL PROPERTIES: Density, hardness, color, melting point, odor, boiling point, chemical formula

Two types of physical properties Extensive properties – are dependent on the amount of a substance present Examples: Mass, length, volume Intensive properties – independent of the amount of a substance present. Substances can often be identified by their intensive properties. Scent, density

Chemical Properties of Matter The ability of a substance to combine with or change into one or more other substances is a chemical property. Examples: Iron forming rust No change or reaction

Observing Properties of Matter Properties (Chemical and physical) of a substance might change depending on the conditions under which they were observed. It’s important to identify the specific conditions (such as temperature and pressure) under which observations are made. Physical and chemical properties depend on these conditions.

Examples of varying chemical and physical properties at different conditions: At standard temperature and pressure H20 is a liquid (physical property) and not chemically reactive (chemical property) and has a density of 1.00 g/cm3 (physical intensive property) At temperatures greater than 100 degrees C, H20 is a gas (physical property) with a density of 0.0006 g/cm3 (physical intensive property) and reacts readily with many different substances (chemical property)

Changes in Matter Physical Changes A change that alters a substance without changing its composition is a physical change. Examples of physical change: Cutting a sheet of paper breaking crystal

A transition of matter from one state to another state is a phase change. Examples of phase change Gas to a liquid Terms such as boil, freeze, condense, vaporize or melt in chemistry typically refer to a phase change in matter. The temperature at which a substance undergoes a phase change is an important physical property; these properties are called the melting point and boiling point.

Chemical Changes A chemical change is a process that involves one or more substances changing a new substance (commonly referred to as a chemical reaction) The new substances formed in the reaction have different chemical compositions and properties from the original substance.

In chemical reactions the starting substances are called reactants and the new substances formed are called products. Terms such as decompose, explode, rust, oxidize, corrode, tarnish, ferment, burn, or rot generally refer to chemical reactions.

C12H22O11 + H2SO4  12C + 11H20 reactants products

Separating Mixtures To really be able to understand a mixture, its components have to be separated out. Because mixtures are physically combined, it requires a physical process to separate them out.

Ways to Separate Mixtures Filtration – A technique that uses a porous barrier to separate a solid from a liquid.

Distillation – a separation technique that is based on differences in the boiling points of the substances involved.

Crystallization – a separation technique that results in the formation of pure solid particles of a substance from a solution containing the dissolved substance. Example – Rock candy being made

Sublimation The process during which a solid changes to vapor without melting/ without going through the liquid phase.

Chromatography A technique that separates the components of a mixture based on the ability of each component to travel or be drawn across the surface of another material.

Elements and Compounds Element - An element is a pure substance that cannot be separated into simpler substances by physical or chemical means.

Compound - Made of two or more different elements that are combined chemically. NaCl - table H2O - water H2O2 – hydrogen peroxide Compounds are different from the elements they are made of and have different properties

Familiarize yourself with the chart on p. 87 in Chapter 3

Law of definite proportions States that a compound is always composed of the same elements in the same proportion by mass, no matter how large or small the sample.

Percent by Mass The ratio of the mass of each element to the total mass of the compound expressed as a percentage Percent by mass= mass of the element/mass of the compound X 100

Practice Problem p.88 #19-22 Complete the problems listed above 2/22/2019 Practice Problem p.88 #19-22 Complete the problems listed above #19 – 15.9% #20 – 5.0% #21 – 25% X and 75% Y #22 – No, Compound I = 11.1% H, Compound II = 5.9% H

You only need to know this one in definition form!!! 2/22/2019 LAW OF MULTIPLE PROPORTIONS = when different compounds are formed by a combination of the same elements, different masses of one element combine with the same relative mass of the other element in a ratio of small whole numbers Ex. Water H2O and hydrogen peroxide H2O2, same relative hydrogen to each other but hydrogen peroxide has twice as much oxygen, ratio of 2:1 Mass ratio of compound I / mass ratio of compound II You only need to know this one in definition form!!!