Pure substances elements

By condensed is meant solid or liquid by chemically homogeneous is meant a pure substance, element or com-... 

F is the number of degrees of freedom, i.e. the number of variables of state such as temperature and pressure that can be varied independently, P is the number of phases and C is the number of components. Components are to be understood as independent, pure substances (elements or compounds), from which the other compounds that eventually occur in the system can be formed. For example ... 

In a titrimetric standardization the solution to be standardized is compared directly or indirectly against a standard substance. Some substances can be weighed accurately, but do not give a solution of known concentration. Others cannot be weighed accurately, but give stable solutions. A primary standard is a pure substance (element or compound) that is stable enough to be stored indefinitely without decomposition, can be weighed accurately without special precautions when exposed to... 

Each of the substances shown in Figure 14 is a pure substance. Every pure substance has characteristic properties that can be used to identify it. Characteristic properties can be physical or chemical properties. For example, copper always melts at 1083°C, which is a physical property that is characteristic of copper. There are two types of pure substances elements and compounds. 

The entropy of any pure substance (element or compound) in its equilibrium state approaches zero at the absolute zero of temperature. 

Pure substance A sample of matter that has constant composition. There are two types of pure substances, elements and compounds. 

Another useful way to classify matter, whether a solid, liquid, or gas, is to indicate whether it is a pure substance or a mixture. A pure substance (often simply referred to as a substance) is one that has a definite composition, such as water or copper. There are two kinds of pure substances elements and compounds. An element is a substance than cannot be broken down into simpler substances by chemical means (like heating to a high temperature). The simplest particle of an element is the atom, and that will be discussed in greater detail in Chapter 3. 

There are different types of pure substances. Elements and compounds are both pure substances. An element is a pure substance that cannot be changed into a simpler form of matter by any chemical reaction. Hydrogen and oxygen, for example, are elements. Alternatively, a compound is a substance resulting from the combination of two or more elements in a definite, reproducible way. The elements hydrogen and oxygen, as noted earlier, may combine to form the compound water, H2O. 

For a pure substance (element or compound), the standard state is usually the most stable form of the substance at 1 atm and the temperature of interest. In this text, that temperature is usually 25°C (298 K). ... 

Mixtures can be separated into pure substances elements and/or compounds. 

There are two kinds of pure substances elements and compounds. An element is a substance that cannot be separated into simpler substances by ordinary chemical methods. Nor can it be created by combining simpler substances. All the matter in the universe is composed of one or more of these fundamental substances. When elements are combined, they form compounds—substances having definite, fixed proportions of the combined elements with none of the properties of the individual elements, but with their own unique set of new physical and chemical properties. 

SECTION 1.2 Matter exists in three physical states, gas, iquid, and sold, which are known as the states of matter. There are two kinds of pure substances elements and compounds. Each element has a single kind of atom and is represented by a chemical symbol consisting of... 

CLASSIFICATIONS OF MATTER (SECTION 1.2) Matter exists in three physical states, gas, liquid, and solid, which are known as the states of matter. There are two kinds of pure substances elements and compounds. Each element has a single kind of atom and is represented by a chemical symbol consisting of one or two letters, with the first letter capitalized. Compounds are composed of two or more elements joined chemically. The law of constant composition, also called the law of definite proportions, states that the elemental composition of a pure compound is always the same. Most matter consists of a mixture of substances. Mixtures have variable compositions and can be either homogeneous or heterogeneous homogeneous mixtures are called solutions. 

Next we examine some fundamental ways to classify materials, distinguishing between pure substances and mixtures and noting that there are two fundamentally different kinds of pure substances elements and compounds. 

It is nsefnl to note a fact here that is discnssed in more detail later in Section 4.11. The smallest particles of some elements and componnds are individual atoms rather than molecules. However, in elements of this type, the individual atoms are all of the same kind, whereas in componnds, two or more kinds of atoms are involved. Thus, the classification of a pure substance as an element or a componnd is based on the fact that only one kind of atom is fonnd in elements and two or more kinds are found in compounds. In both cases, the atoms may be present individnally or in the form of homoatomic molecules (elements) or heteroatomic molecules (compounds). Some common household materials are pure substances (elements or componnds), snch as alnminnm foil, baking soda, and table salt. 

Some elements do not behave as if their smallest particle is a single atom. For example, at common temperatures seven elements form diatomic molecules. A molecule is the tiniest independent particle of a pure substance—element or compound— in a sample of that substance. Di- is a prefix that means two. Thus, a diatomic molecule consists of two atoms that are chemically bonded to each other. This molecule is a formula unit of the element. Its chemical formula is the elemental symbol followed by a subscript 2. For example, the chemical formula of hydrogen (symbol H) is H2. 

A pure substance is matter that has a fixed or constant composition. There are two kinds of pure substances elements and compounds. An element, the simplest type of a pure substance, is composed of only one type of material, such as silver, iron, or aluminum. Every element is composed of atoms, which are extremely tiny particles that make up each type of matter. Silver is composed of silver atoms, iron of iron atoms, and aluminum of aluminum atoms. A full list of the elements is found on the inside front cover of this text. 

Classify each of the following as a pure substance (element or compound) or a mixture (homogeneous or heterogeneous) ... 

Define the following terms solid, liquid, gas, pure substance, element, compound, homogeneous mixture, heterogeneous mixture, solution, chemical change, physical change. 

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