Chemistry

Suspension

A heterogeneous mixture that separates into layers over time. Scatters light, can be filtered

Conductivity

A material's ability for allowing heat to flow through it. Materials with high conductivity like metals, are called conductors. -- usually good for electricity also

Filtration

A method to separate mixtures that is based on the size of their particles.

Solution

A solution forms when substances dissolve and form a homogeneous mixture. -- small particles, homogeneous, not scatter light, cant be filtered

Element

A substance that cannot be broken down into simpler substances. An atom is the smallest particle of an element. An element has a fixed composition because it contains only one type of atom. At room temperature, most elements are solid and are represented by symbols.

Compound

A substance that is made from two or more simpler substances and can be broken down into those simpler substances. A compound always contains two or more elements joined in a fixed proportion.

Flammability

An example of a chemical property and it is the material's ability to burn in the presence of oxygen.

Chemical Properties

Any ability to produce a change in the composition of matter. Chemical Properties can be observed only when the substances in a sample of matter are changing into different substances.

Physical Properties

Any characteristic of a material that can be observed or measured without changing the composition of the substances in the material. Like: Boiling point, conductivity, malleability, hardness, melting point, density or viscosity. Useful to know because 1. Helps identify a material 2. Helps to choose a material for a specific purpose and 3. Helps to know how to separate the substances in a mixture

Reactivity

Example of a chemical property that describes how readily a substance combines chemically with other substances. Like oxygen is highly reactive.

Distillation

Is a process that separates substances in a solution based on their boiling points.

Density

Is the ratio of the mass of a substance to it's volume. Density can be used to test the purity of a substance.

Colloid

It contains some particles that are intermediate in size between the small particles in a solution and the larger particles in the solution. -- heterogeneous, scatters light, cannot be filtered

Properties of mixture

Less uniform than the properties of a substance and can vary because the composition of a mixture is not fixed. There are two types of mixtures: Heterogeneous and Homogeneous. A mixture can be classified as a solution, a suspension or a colloid. This classification is based on the size of the mixtures largest particles.

Pure Substance

Matter that always has exactly the same composition. Every sample has fixed and uniform composition and can be classified into two categories: Elements and Compounds.

Chemical Change

Occurs when a substance reacts and forms one or more new substances. Three common types of evidence for a chemical change are: 1. Change in color, 2. The production of a gas and 3. The formation of a precipitate or a solid that separates from a liquid mixture. Not always easy to tell a chemical change from a physical change when a chemical change happens, the composition of the matter changes. (Different than a physical change where the composition of the matter remains the same).

Physical Change

Occurs when some of the properties of a material change, but the substances in the material remain the same. Important: Some physical changes can be reversed and some cannot.

Malleability

The ability of a solid to be hammered without shattering. Most metals are malleable.

Heterogeneous Mixture

The parts of the mixture are noticeably different from one another.

Homogeneous Mixture

The substances are SO evenly distributed that it is difficult to tell one substance in the mixture from another. A homogeneous mixture appears to contain only one substance

Boiling Point

The temperature at which a substance boils. (liquid to gas)

Melting Point

The temperature at which a substance changes from solid to liquid. -- melting candle

Viscosity

The tendency of a liquid to keep from flowing. The greater the viscosity, the slower the liquid moves.

Hardness

property that reflects hardness of substance. Test is scratching, hardest substance is diamonds