For example, water a compound can be decomposed into hydrogen and oxygen both elements by a process called electrolysis. A similar technique is used on a vast scale to obtain pure aluminum, an element, from its ores, which are mixtures of compounds. Because a great deal of energy is required for electrolysis, the cost of electricity is by far the greatest expense incurred in manufacturing pure aluminum.
Thus recycling aluminum is both cost-effective and ecologically sound. Identify each substance as a compound, an element, a heterogeneous mixture, or a homogeneous mixture solution. Matter can be classified according to physical and chemical properties. Matter is anything that occupies space and has mass.
The three states of matter are solid, liquid, and gas. A physical change involves the conversion of a substance from one state of matter to another, without changing its chemical composition. Most matter consists of mixtures of pure substances, which can be homogeneous uniform in composition or heterogeneous different regions possess different compositions and properties.
Pure substances can be either chemical compounds or elements. Compounds can be broken down into elements by chemical reactions, but elements cannot be separated into simpler substances by chemical means.
The properties of substances can be classified as either physical or chemical. Scientists can observe physical properties without changing the composition of the substance, whereas chemical properties describe the tendency of a substance to undergo chemical changes chemical reactions that change its chemical composition. Physical properties can be intensive or extensive.
Intensive properties are the same for all samples; do not depend on sample size; and include, for example, color, physical state, and melting and boiling points. Extensive properties depend on the amount of material and include mass and volume. The ratio of two extensive properties, mass and volume, is an important intensive property called density. Modified by Joshua Halpern Howard University.
Learning Objectives To classify matter. Pure Substances and Mixtures A pure chemical substance is any matter that has a fixed chemical composition and characteristic properties. Under a microscope, whole milk is actually a heterogeneous mixture composed of globules of fat and protein dispersed in water.
Figure used with permission from Wikipedia Homogeneous mixtures solutions can be separated into their component substances by physical processes that rely on differences in some physical property, such as differences in their boiling points.
The solution of salt in water is heated in the distilling flask until it boils. The resulting vapor is enriched in the more volatile component water , which condenses to a liquid in the cold condenser and is then collected in the receiving flask.
Video can be found here: www. In this state, the weak attractive forces within the liquid are unable to hold the particles into a mass with a definite shape. Thus a liquid's shape takes on the shape of any particular container that holds it. A liquid has a definite volume but not a definite shape.
Compared to to the gaseous state there is less freedom of particle movement in the liquid state since the moving particles frequently are colliding with one another, and slip and slide over one another as a result of the attractive forces that still exist between the particles, and hold the particles of the liquid loosely together.
At a given temperature the volume of the liquid is constant and its volume typically only varies slightly with changes in temperature. In the gas phase, matter does not have a fixed volume or shape. This occurs because the molecules are widely separated with the spaces between the particles typically around ten times further apart in all three spatial directions, making the gas around times less dense than the corresponding liquid phase at the same temperature.
A phase is a uniform portion of mater. As the temperature of a gas is increased, the particles to separate further from each other and move at faster speeds. The particles in a gas move in a rather random and independent fashion, bouncing off each other and the walls of the container.
Being so far apart from one another, the particles of a real gas only weakly attract each other such that the gas has no ability to have a shape of its own. The extremely weak forces acting between the particles in a gas and the greater amount of space for the particles to move in results in almost independent motion of the moving, colliding particles. The particles freely range within any container in which they are put, filling its entire volume with the net result that the sides of the container determine the shape and volume of gas.
If the container has an opening, the particles heading in the direction of the opening will escape with the result that the gas as a whole slowly flows out of the container. Besides of the three classical states of matter, there are many other states of matter that share characteristics of one more of the classical states of matter.
Most of these states of matter can be put into three categories according to the degrees in varying temperature. At room temperature, the states of matters include liquid crystal, amorphous solid, and magnetically ordered states. At low temperatures the states of matter include superconductors, superfluids, and Bose-Einstein condensate state of matter. At high temperatures the states of matter include, plasma and Quark-gluon plasma.
These other states of matter are not typically studied in general chemistry. Introduction A substance is a sample of matter whose physical and chemical properties are the same throughout the sample because the matter has a constant composition. Classifying Matter Evidence suggests that substances are made up of smaller particles that are ordinarily moving around.
An illustration of the helium atom, depicting the nucleus pink and the electron cloud distribution black. The nucleus upper right in helium-4 is in reality spherically symmetric and closely resembles the electron cloud, although for more complicated nuclei this is not always the case.
Image used with permissin from Wikipedia. Heterogeneous Mixtures: separation of sand and water separation of salad dressing various mixtures within a rock Mixtures that fall between a solution and a heterogeneous mixture are called colloidal suspensions or just colloids. Separation of Mixtures Most substances are naturally found as mixtures, therefore it is up to the chemist to separate them into their natural components.
The homogeneous mixture starts out in the left flask and is boiled. The vapor then travels down chilled tube on the right and condenses back into a liquid and drips into the flask. An atom is so light that its mass is also difficult to imagine. It is rare to find collections of individual atoms. Only a few elements, such as the gases helium, neon, and argon, consist of a collection of individual atoms that move about independently of one another.
Other elements, such as the gases hydrogen, nitrogen, oxygen, and chlorine, are composed of units that consist of pairs of atoms Figure 1. One form of the element phosphorus consists of units composed of four phosphorus atoms. The element sulfur exists in various forms, one of which consists of units composed of eight sulfur atoms. These units are called molecules. A molecule consists of two or more atoms joined by strong forces called chemical bonds.
The atoms in a molecule move around as a unit, much like the cans of soda in a six-pack or a bunch of keys joined together on a single key ring. A molecule may consist of two or more identical atoms, as in the molecules found in the elements hydrogen, oxygen, and sulfur, or it may consist of two or more different atoms, as in the molecules found in water. Each water molecule is a unit that contains two hydrogen atoms and one oxygen atom.
Each glucose molecule is a unit that contains 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms. Like atoms, molecules are incredibly small and light. If an ordinary glass of water were enlarged to the size of the earth, the water molecules inside it would be about the size of golf balls. Water consists of the elements hydrogen and oxygen combined in a 2 to 1 ratio. Water can be broken down into hydrogen and oxygen gases by the addition of energy.
One way to do this is with a battery or power supply, as shown in Figure 1. The breakdown of water involves a rearrangement of the atoms in water molecules into different molecules, each composed of two hydrogen atoms and two oxygen atoms, respectively. Two water molecules form one oxygen molecule and two hydrogen molecules.
The two gases produced have distinctly different properties. Oxygen is not flammable but is required for combustion of a fuel, and hydrogen is highly flammable and a potent energy source. How might this knowledge be applied in our world? One application involves research into more fuel-efficient transportation. Fuel-cell vehicles FCV run on hydrogen instead of gasoline Figure 1. They are more efficient than vehicles with internal combustion engines, are nonpolluting, and reduce greenhouse gas emissions, making us less dependent on fossil fuels.
FCVs are not yet economically viable, however, and current hydrogen production depends on natural gas. If we can develop a process to economically decompose water, or produce hydrogen in another environmentally sound way, FCVs may be the way of the future. Imagine how different your life would be without cell phones Figure 1. Cell phones are made from numerous chemical substances, which are extracted, refined, purified, and assembled using an extensive and in-depth understanding of chemical principles.
The display screen is made from a specially toughened glass silica glass strengthened by the addition of aluminum, sodium, and potassium and coated with a material to make it conductive such as indium tin oxide. The circuit board uses a semiconductor material usually silicon ; commonly used metals like copper, tin, silver, and gold; and more unfamiliar elements such as yttrium, praseodymium, and gadolinium.
The battery relies upon lithium ions and a variety of other materials, including iron, cobalt, copper, polyethylene oxide, and polyacrylonitrile. As an Amazon Associate we earn from qualifying purchases. Want to cite, share, or modify this book? Air, a mixture of mainly nitrogen and oxygen, is a gaseous solution. Show Answer. Another way to classify matter is to describe it as a solid, a liquid, or a gas, which was done in the examples of solutions.
These three descriptions, each implying that the matter has certain physical properties, represent the three phases of matter. A solid has a definite shape and a definite volume. Liquids ordinarily have a definite volume but not a definite shape; they take the shape of their containers.
Gases have neither a definite shape nor a definite volume, and they expand to fill their containers. We encounter matter in each phase every day; in fact, we regularly encounter water in all three phases: ice solid , water liquid , and steam gas.
We know from our experience with water that substances can change from one phase to another if the conditions are right. Typically, varying the temperature of a substance and, less commonly, the pressure exerted on it can cause a phase change , a physical process in which a substance goes from one phase to another Figure 1.
Phase changes have particular names depending on what phases are involved, as summarized in Table 1. Figure 1. Explain the differences between the physical properties of matter and the chemical properties of matter. What is the difference between a heterogeneous mixture and a homogeneous mixture?
Give an example of each. Give at least two examples of a phase change and state the phases involved in each. Does each statement refer to a chemical property or a physical property?
Define element. How does it differ from a compound? Define compound. How does it differ from an element? Identify each substance as an element, a compound, a heterogeneous mixture, or a solution. Identify each material as an element, a compound, a heterogeneous mixture, or a solution.
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