Chemical properties and physical properties are characteristics of matter that can be used to help identify and describe it. Chemical properties are those that you can observe only if matter experiences a chemical change or chemical reaction. In other words, you need to change the chemical identity of a sample in order to observe and measure its chemical properties.
Why Is It Important to Know the Chemical Properties of a Sample?
It's important to know the chemical properties of a sample because this information can be used to:
- Classify it
- Identify an unknown sample
- Purify it
- Separate it from other substance
- Predict its behavior
- Predict its uses
Let's take a closer look at some examples of chemical properties.
Toxicity as a Chemical Property
Toxicity is an example of a chemical property. Toxicity is how dangerous a chemical is to your health, a particular organ, another organism, or to the environment. You can't tell by looking at a chemical whether or not it is toxic. How poisonous a substance is depends on the situation, so this is a property that can only be observed and measured by exposing an organic system to a sample. The exposure causes a chemical reaction or set of reactions. The net result of the chemical changes is the toxicity.
Flammability as a Chemical Property
Flammability is a measure of how readily a sample ignites or how well it can sustain a combustion reaction. You don't know how easily something will burn until you try to ignite it, so flammability is an example of a chemical property.
Chemical Stability
Chemical stability is also known as thermodynamic stability. It occurs when a substance is at chemical equilibrium in its environment, which is its lowest energy state. This is a property of matter that is determined by its specific conditions, so it can't be observed without exposing a sample to that situation. Thus, chemical stability fits the definition of a chemical property of matter.
Chemical stability is related to chemical reactivity. While chemical stability pertains to a given set of circumstances, reactivity is a measure of how likely a sample is to participate in a chemical reaction under a variety of conditions and how quickly a reaction might proceed.
Oxidation States or Oxidation Number
Each element has a preferred set of oxidation states or oxidation numbers. It is a measure of the loss of electrons or oxidation of an atom in a compound. Although integers (e.g., -1, 0, 2) are used to describe oxidation states, the true level of oxidation is more complicated. Because oxidation can't be known until an element participates in a chemical reaction to form chemical bonds, this is a chemical property.
More Examples of Chemical Properties
There are many chemical properties of matter. In addition to toxicity, flammability, chemical stability, and oxidation states, other chemical properties include:
- Enthalpy of formation
- The heat of combustion
- Electronegativity
- Coordination number
- Solubility
- Acidity/basicity
- The degree of ionization
Basically, a chemical property is a characteristic that may only be observed as a result of a chemical reaction.