Physical and Chemical Properties.docx

Introduction to Physical and Chemical Properties Matter is defined as anything that has mass and takes up space. All types of matter have certain properties that are unique to that matter. These properties can be divided into two separate categories: physical properties and chemical properties. What...

Introduction to Physical and Chemical Properties Matter is defined as anything that has mass and takes up space. All types of matter have certain properties that are unique to that matter. These properties can be divided into two separate categories: physical properties and chemical properties. What is a physical property? The physical property definition is: the properties of matter are generally things that describe the property with visual inspection or taking some kind of measurement, such as length or mass. There is no change to the chemical composition of a substance when examining its physical properties. What is a chemical property? The chemical properties of a type of matter refer to how it interacts with other substances during a chemical process or reaction. It is the combination of physical and chemical properties of a matter that give the matter its identity. Matter can exist as a pure substance like an element, such as hydrogen gas, a compound, such as water made of hydrogen and oxygen, or in a mixture where two or more substances are combined, but not interacting in a chemical process, such as ocean water. Ocean water is a mixture (solution) of sodium chloride and water existing together, but not chemically reacting. What are Physical Properties? Physical properties are properties that can be determined without changing the identity of the matter. Physical properties can be observed or measured without any changes to the chemical composition. Visual observation, a balance, a ruler, or another method of measurement, can be used to determine physical properties. None of the methods used will have any affect on the chemical composition of a substance. Some physical properties examples are: Color Texture Mass Length Shape Density Matter will sometimes undergo physical changes. This happens when a particular type of matter changes state from solid to liquid, liquid to gas, gas to liquid, liquid to solid, or even solid to gas. These phase changes, known as melting, freezing, vaporization, condensation, and sublimation, have no affect on the chemical composition of the substance, therefore, they are not chemical changes. Phase changes, or changes of state, occur when energy is added to or taken from the substance. For example, an ice cube left on a counter will absorb heat energy from its surroundings and eventually melt to become liquid water. In both the solid state and liquid state, it is still water. No chemical reaction occurred to change the identity of the substance. However, sometimes the physical properties change during a phase change. An ice cube may have a square shape, but when it melts to become a puddle of liquid water, it most definitely takes a different shape. Both shapes are still water. What are Chemical Properties? Physical and chemical properties are different in that a chemical property refers to how a type of matter interacts with another type of matter. Chemical properties go hand in hand with chemical changes. It isn't possible to discuss a chemical property without taking into account how the matter goes through a chemical change. Some chemical property examples are: Reactivity pH Corrosion Conductivity When matter undergoes a chemical change, the chemical properties of the original substance determine how the change will proceed. The atoms of the matter are rearranged with other matter, changing the chemical composition of the original substance. The atoms are still there, just in a new combination. This then changes all the properties to fit the newly created matter. For instance, copper is highly reactive with oxygen in the presence of water or water vapor. Copper goes though a chemical process, called oxidation, that changes the copper metal to copper oxide. It is this change that makes the Statue of Liberty have it's characteristic green color. The Statue of Liberty is made of copper. Over time the metal reacted with the oxygen in the air and oxidized, changing its color to green. Difference Between Physical and Chemical Properties What is the difference between physical properties and chemical properties? The difference between physical and chemical properties is that physical properties can be observed or measured without any sort of reaction process that changes the identity of the matter. The chemical properties of a type of matter can only be determined by putting the matter through some sort of reaction or process that ultimately changes the composition of the substance. Physical properties: can be observed can be measured with a tool can change when a substance changes state have nothing to do with one type of matter interacts with another type Chemical properties: happen at the atomic level occur when one substance reacts with another can't always be observed are not easily measured with a tool Examples of Physical and Chemical Properties The physical and chemical properties of matter depend solely on the type of matter in question. Matter is defined as anything that has mass and takes takes up space. Matter can be living or non-living. It can be organic (containing carbon) or inorganic (no carbon present). Basically everything is matter; from the tiniest insect to the largest tree. Humans, animals, cars, houses, grass, and food are all types of matter in every day life. Trees, grass, fruit, soil, and air all represent different types of matter. Is Color a Physical or Chemical Property? Is color a physical or chemical property? Color is an observable characteristic of matter, therefore, color is a physical property, not a chemical property. Color is observed as the portion of the visible electromagnetic spectrum that is reflected by the substance. If an apple is red, it is because the matter that makes up the apple absorbs all visible colors except red. That makes it appear red to the person observing it. The grass is green because the green wavelengths are reflected and not absorbed. Is Density a Chemical Property? The density of a substance is how much mass of that substance is packed into a given volume. Density is calculated by dividing the mass of that substance by its volume. Is density a chemical property? Density is not a chemical property; it is a physical property that can be measured and observed. The density of a substance at a given phase will not change no matter how much or how little there is in a sample. The only time density will/can change is when a change of state occurs. Density generally decreases as substance melts then vaporizes. The solid phase of a substance tends to be more dense than the liquid phase. Likewise, the liquid phase tends to be more dense than the gas phase. This is because the particles in a solid are more orderly and fixed in position than a liquid or a gas. Liquids have some freedom to flow past each other and gases have the freedom to move wherever they want. Therefore, the solid, with its fixed structure packs more mass into a given volume than a liquid or a solid. One exception to this rule is water. When liquid water freezes, it's v-shaped molecules trap air between them as they settle into their fixed position. The trapped air actually decreases the density of the ice, compared to the liquid form of water. Water reaches it's maximum density at 4 degrees C, but actually freezes solid at 0 degrees C. Is pH a Chemical Property? Is pH a chemical property? pH is a chemical property that is determined by how many H+ ions are released from a type of matter when it is dissolved in water. Substances that release many free H+ ions are considered to be acidic. Substances that break down in water and produce OH- ions are considered to be bases. pH is the measure of how many H+ ions are present in terms of concentration. The higher the concentration of H+, the more acidic the solution is. The lower the concentration of H+ and higher the concentration of OH-, the more basic it is. This makes pH a chemical property because it depends on how a solid or liquid substance interacts with water when mixed together. The pH scale runs from 0-14. Matter with a pH of 7, like pure water is considered to be neutral. Anything that has a pH of 0 up to 7 is acidic and anything above 7 and up to 14 is basic. Stomach acid is a strong acid at a pH of about 2. Soaps and detergents are more basic with pH's around 8, depending on the product. Is Reactivity a Physical or Chemical Property? Is reactivity a physical or chemical property? Reactivity is the ability of a type of matter to interact with another type of matter to create something entirely new. All the same atoms and amounts of the atoms remain, but they have just rearranged themselves during a chemical process. This means that reactivity is a chemical property, not a physical property. Sodium metal is highly reactive with water. When they come into contact with each other, the chemical response is swift and violent, causing a reaction to occur. Hydrogen gas and oxygen gas will combine under the right conditions to form water. There are five types of chemical reactions that can occur, depending on what types of matter come into contact: Combustion: a hydrocarbon is destroyed in the presence of oxygen, producing heat, carbon dioxide, and water vapor Synthesis: two types of matter join in a chemical process to make one new type Decomposition: a chemical change where one type of matter is broken down in to two or more different types Single replacement and double replacement: chemical processes where two types of matter swap out different atoms and become new types of matter Is Corrosion a Physical or Chemical Property? Is corrosion a physical or chemical property? Corrosion occurs when oxygen reacts with the surface atoms of a metal, destroying the integrity of the metal matter. This means corrosion is not a physical property, but is a chemical property because there is an interaction between two substances in which change occurs on a molecular level. Rusting steel is a common example of corrosion. Salt water destroying bridge supports is another common example. Corrosion can cause large amounts of damage to materials used in infrastructure, such as power line supports and transportation. Is Mass a Physical or Chemical Property? Is mass a physical or chemical property? Mass is a measure of how much matter is present in a sample of a substance. Mass is measurable using a balance and can be observed and recorded. This means that mass is a physical property, not a chemical property. The mass of a substance is influenced not only by how much of it you have, but also how dense the matter is. Equal masses of two types of matter do not have to be equal in amount or sample size. For example, a kilogram of feathers and a kilogram of sugar have the same mass, but it takes far more feathers to make the same mass as it does sugar. Lesson Summary Matter is anything that has mass and takes up space. All matter has specific physical properties and chemical properties. Physical properties have nothing to do with a change in the composition of a substance, while chemical properties deal directly with changes in composition. Matter can be divided into two types; pure substances, such as elements, and compounds, which are combinations of elements to make new matter. Salt, limestone and water are examples of compounds. Matter can also exist in mixtures, where several compounds co-exist, such as in ocean water. Physical properties of matter include color, mass, and density. Chemical properties include pH and reactivity. Corrosion, such as the rusting of iron, is a particularly destructive chemical property.