Matter

Defining Matter

Matter is anything that has mass or volume

  • Mass is the measure of particles in a substance. The gram is the SI unit of mass.
  • Volume is the space that a substance occupies. The unit of measure of volume is derived from Lengh X Width X Height. (1 cubic centimeter= 1 milliliter). The basic SI unit of liquid volume is the liter. the basic SI unit of length is the meter. Therefore, the cubic meter is the basic unit of solid volume.
  • Density is the mass per volume of a substance or mass divided by volume.

The mass of both blocks is 100 grams.

The volume of the block on the left is 1000 ml.

The volume of the block on the right is 100 g.

Density is the mass divided by the volume.

The density of the block on the left is 0.1 g/mL.

The density of the block on the right is 1.0 g/mL.

The material in the right block is more dense than the material in the left block.

Properties of Matter

Physical Properties of Matter

Physical properties can be used to identify a pure substance. Physical properties can be observed without any change in the substances chemical composition. Physical properties can be used to separate substances in a mixture.

  • melting point
  • boiling point
  • color
  • density
  • magnetism
  • crystalline shape
  • malleability
  • ductility
  • luster
  • refractive index

Categories of Matter

Substances can be divided into two categories of matter: pure substances or mixtures.

Pure Substances

Mixtures

  • Pure substances are all one type of matter
  • Elements are the smallest complete units of a pure substance that cannot be physically or chemically broken down into other substances.
  • Compounds are a combination of two or more elements that have interacted chemically to make a new substance.
  • Mixtures are two or more types of substances that are in the same place but not chemically combined.
  • Solutions are special mixtures that are so well mixed that have the appearance of being a single substance.

Changes in Matter

Physical Change

Chemical Change

  • Physical change alters the form of a substance but not the chemical characteristics.
  • Phase changes are an example of a physical change.
  • No new substance forms.
  • Chemical changes occur when one or more substances combine or breakdown to become something new.
  • Chemical activity is the ability of a substance to undergo a specific change.
  • No new substance forms.

Kinetic Theory of Matter

Phases of Matter

The phase of matter of a substance depends on the average kinetic energy or energy of movement of molecules or atoms of a substance. Temperature is a measure of average kinetic energy. Therefore, the phase of matter of a substance depends on the temperature of the substance. A transfer of heat to a substance will increase the kinetic energy of the substance. A transfer of heat from a substance will decrease the kinetic energy of the substance.

Temperature scales include Fahrenheit, Celsius, and Kelvin. The Fahrenheit scale is based on a freezing point of water at 32 degrees and a boiling point at 212 degrees. The advantage of celsius is that it is based on 100 units. The freezing point of water at 100 degrees and the boiling point at 100 degrees. This is also why the Celsius scale is ofter called the centigrade scale (100 units). The Kelvin scale is based on absolute zero, the coldest possible temperature. The advantage of the Kelvin scale is that in the Kelvin scale there are no negative temperatures. Celsius and Kelvin are used in scientific measurements.

Energy and the States of Matter

Solids have a definite volume and a definite shape. Kinetic energy is low. Molecules of solids vibrate.

Liquids have a definite volume but no definite shape, they take the shape of their container. Kinetic energy is higher than in solids. Molecules slide over each other or have weak attractions (bonds).

Gases have no definite volume and no definite shape, they take the shape of their container. Kinetic energy is high compared to liquids. Molecules become more energetic as temperature increases. The volume of gas depends on pressure and temperature.

Plasmas are the most energized form of matter. Atoms ionize becoming streams of highly energetic subatomic particles. Lightening and fluorescent lights are examples of plasma.

Phase Changes

Phases of Water

Melting point is the temperature at which a solid becomes a liquid.

Boiling point is the temperature at which a liquid boils. Liquids will vaporize with boiling.

Phase changes that release energy are exothermic. Phase changes that absorb energy are endothermic.

Exothermic Phase Changes Release Heat Energy

Endothermic Phase Changes Absorb Heat Energy

Freezing

Condensation

Deionization

Melting

Boiling

Ionization

Notice that the freezing point ant melting point are at the same temperature. Condensation and boiling occur at the same temperature. Changes in heat energy drive phase changes.

Phase change temperatures can be used to identify substances and to separate mixtures of substances.

NBote: Vaporization can occur below the boiling point. Vaporization if the loss of surface molecules of a liquid.

Hint

Melting point=Freezing point

Boiling point = Condensation point

Note that the temperature plateaus become stationary during a phase change