Хімічні та фізичні властивості

Though there are 118 known elements, most of these elements are incredibly rare, and almost everything you see or interact with on a daily basis is made out of only a few elements. Oxygen is the most abundant element in both the Earth and your body. So why are you and the earth different? The answer is chemical and physical properties.

Simply put, properties are just testable descriptions of substances. Unlike the earth, you aren't large enough for your gravity to cause objects to orbit around you- that's a physical property. Also unlike the earth, the majority of your body is liquid- again, a physical property. When you're outside in the sunlight for a long time, you can get sunburnt, while the Earth has spent millennia outdoors without sunscreen. This is a chemical property. What's the difference between physical and chemical properties?

Physical properties are usually the general properties you notice most quickly about something. Size, state of matter, color, mass, density, and strength are all examples of physical properties. These values can be determined by tests that don't destroy the substance tested- noticing the color or size of an object doesn't change it in any way. The same element has different physical properties in different phases or in different compounds.

What Are Chemical Properties?

These are properties which are specific to the chemical make-up of a substance. Usually, these properties cannot be determined by looking at or touching the substance. Chemical properties are often observed during or after a chemical reaction has taken place.

Types of Chemical Properties

There are many properties a chemical can have that are dependent on its chemistry. Here are a few examples:

• Solubility: the ability for a substance to dissolve in different liquids (solvents) such as water.

• Flammability: how easily the material will catch fire and burn without a fuel source, like gasoline.

• Bond formation: the type of bonds formed and how easily the bonds are created/broken.

• Acidity/Basicity: the amount of protons (H$^+$) in solution when a chemical is solvated determines acidity/basicity. The more hydrogen ions, the more acidic. Hydroxide (OH$^-$) in solution indicates basicity. The more hydroxide, the more basic.

• Coordination Number: the number of atoms surrounding another atom is the coordination number. These can be electrostatic interactions (ionic bonds) or covalent bonds. Some atoms create as few as one or two bonds. Transition metals, like iron (Fe), can have many bonds.

• Toxicity: the harmfulness of a chemical to living things. Some chemicals can cause sickness and even death. The amount of the chemical also affects how harmful it is.

Example: Chemical Properties of Sodium Chloride (NaCl)

Sodium chloride ($NaCl$), also known as table salt, is a chemical compound. It has high solubility in water and low solubility in organic solvents.

$NaCl$ is not flammable itself. But, when it is passed through a flame it colors the flame yellow.

The bond of this compound is an ionic bond which in solutions forms sodium and chloride ions ($Na^+$ and $Cl^-$).

It is neither acidic nor basic. However, the compound forms in a reaction between an acid and a base. When hydrochloric acid ($HCl$) reacts with sodium hydroxide ($NaOH$), they produce sodium chloride ($NaCl$) and water ($H_2O$).

The ionic compound, $NaCl$, forms a crystal lattice. Each ion ($Na^+$ and $Cl^-$) has 6 opposite charge ions next to it. So each atom has a coordination number of 6.

Sodium Chloride is not considered a toxic substance and is safe enough to eat. As with any chemical, too much can become toxic, even water.

(Video) Physical vs. Chemical Properties - Explained

by Chem Academy

This video will teach you about physical properties and chemical properties of substances. These properties relate to how matter behaves, and how it can undergo chemical changes to form a new substance. Finally, you'll have a chance to practice what you know by deciding what type of property something is.