3: Matter and Energy
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- 3.1: What is Matter?
- Matter is anything that has mass and volume (takes up space). For most common objects that we deal with every day, it is fairly simple to demonstrate that they have mass and take up space. You might be able to imagine, however, the difficulty for people several hundred years ago to demonstrate that air has mass and volume. The basic building blocks of matter are atoms, of which 118 unique ones have been identified. These atoms can then combine to form millions of different molecules.
- 3.2: Physical States of Matter
- Three states of matter exist - solid, liquid, and gas. Solids have a definite shape and volume. Liquids have a definite volume, but take the shape of the container. Gases have no definite shape or volume.
- 3.3: Composition of Matter
- One useful way of organizing our understanding of matter is to think of a hierarchy that extends down from the most general and complex to the simplest and most fundamental. Matter can be classified into two broad categories: pure substances and mixtures. A pure substance is a form of matter that has a constant composition and properties that are constant throughout the sample. A material composed of two or more substances is a mixture.
- 3.4: Physical and Chemical Properties
- A physical property is a characteristic of a substance that can be observed or measured without changing the identity of the substance. Physical properties include color, density, hardness, and melting and boiling points. A chemical property describes the ability of a substance to undergo a specific chemical change.
- 3.5: Physical and Chemical Changes
- Change is happening all around us all of the time. Chemists learn a lot about the nature of matter by studying the changes that matter can undergo. Just as chemists have classified elements and compounds, they have also classified types of changes. Changes are either classified as physical or chemical changes.
- 3.6: Conservation of Mass
- The law of conservation of mass states that matter can not be created or destroyed in a chemical reaction. So the mass of all of the products formed equals the mass of all of the reactants that were reacted together. Mass and matter may not be able to be created or destroyed, but it can change forms to other substances like liquids, gasses, solids, etc.
- 3.7: Energy
- When we speak of using energy, we are really referring to transferring energy from one place to another. Although energy is used in many kinds of different situations, all of these uses rely on energy being transferred in one of two ways. Energy can be transferred as heat or as work.
- 3.8: Energy and Chemical and Physical Change
- Phase changes involve changes in energy. All chemical reactions involve changes in energy. This may be a change in heat, electricity, light, or other forms of energy. Reactions that absorb energy are endothermic. Reactions that release energy are exothermic.
- 3.9: Temperature
- Three different scales are commonly used to measure temperature: Fahrenheit (expressed as °F), Celsius (°C), and Kelvin (K).
- 3.10: For Future Use
- 3.11: Exercises
Thumbnail Chapter 3: Rocket Launch (ChemLancer adaptation of NASA via Giphy)