Let's start by understanding what gases are. Gases are one of the states of matter, along with solids and liquids. Unlike solids, which have a fixed shape and volume, and liquids, which have a fixed volume but not a fixed shape, gases have neither a fixed shape nor a fixed volume. This means that gases can expand to fill the entire container they are in.
Properties of Gases
Gases have several unique properties that distinguish them from solids and liquids:
Expansion: Gases expand to fill the entire volume of their container.
Fluidity: Gases can flow and move past one another.
Compressibility: Gases can be compressed into a smaller volume under pressure.
Diffusion: Gases mix and spread out evenly when not confined to a specific volume.
The behavior of gases is governed by the gas laws, which describe the relationship between the pressure, volume, and temperature of a gas. The three main gas laws are:
Gases can also mix together to form gas mixtures. The composition of a gas mixture can be homogeneous (uniform throughout) or heterogeneous (non-uniform). Some common gas mixtures include air (a mixture of nitrogen, oxygen, carbon dioxide, and other gases) and natural gas (a mixture of methane, ethane, propane, and other hydrocarbons).
Applications of Gases
Gases have numerous applications in our daily lives and various industries. Some common uses of gases include:
As a fuel for heating and cooking (e.g., natural gas, propane)
In refrigeration and air conditioning systems (e.g., refrigerant gases)
In medical applications (e.g., oxygen for respiratory support)
The Living Environment: Students understand that cells are the basic unit of life, that all life as we know it has evolved through genetic transfer and natural selection to create a great diversity of organisms, and that these organisms create interdependent webs through which matter and energy flow. Students understand similarities and differences between humans and other organisms and the interconnections of these interdependent webs.
Cells: Students describe how living things are made up of one or more cells and the ways cells help organisms meet their basic needs.
Give examples of organisms that consist of a single cell and organisms that are made of a collection of cells.