7-5 Chemical Nature of Matter PART 2 by Cyndee Crawford October 2014 7-5 The student will demonstrate an understanding of the classifications and properties of matter and the changes that matter undergoes. (Physical Science)
7-5.7 Identify the reactants and products in chemical equations.
Page : Reactants & Products When a substance is broken apart or when substances are combined and at least one new substance is formed, a chemical reaction has occurred.
Page : Reactants & Products Chemical Equation It is used to represent a chemical reaction that has occurred. It contains the chemical names or the chemical formulas of the substances that are involved in the reaction.
Page : Reactants & Products Chemical Equation An arrow is used to distinguish between the substances that are broken apart or combined from the substances that are formed in the reaction. The arrow can be translated as yields or makes.
Page : Reactants & Products Reactant Substances broken apart or combined in a chemical reaction are reactants. Reactants are located on the left side of the arrow in a chemical equation.
Page : Reactants & Products Product New substances formed in a chemical reaction. Products are located on the right side of the arrow.
Page : Reactants & Products Example: When Hydrogen gas and Oxygen combine, Water is the formed. o The reactants are Hydrogen gas and Oxygen. o The product is Water. o 2H 2 + O 2 2H 2 O
7-5.8 Explain how a balanced chemical equation supports the law of conservation of matter.
Page : Law of Conservation of Matter Law of Conservation of Matter: The amount of matter does not change during a chemical reaction. The atoms are rearranged to form new substances in a chemical reaction.
Page : Law of Conservation of Matter Law of Conservation of Matter: The law of conservation of matter states that matter can neither be created nor destroyed, but can be changed in form.
Page : Law of Conservation of Matter Law of Conservation of Matter: Because matter can neither be created nor destroyed, the total mass before and after the reaction must be the same. A balanced chemical equation has the same number of each kind of atom on the reactant side as on the product side.
Page : Law of Conservation of Matter Law of Conservation of Matter: To determine whether a chemical equation is balanced, you must look at the subscript and the coefficient. o A coefficient is the number that comes before the chemical formula. o It indicates the number of particles that participate in the reaction.
Page : Law of Conservation of Matter Law of Conservation of Matter: In order to determine whether an equation is balanced, multiply the coefficient by the subscript in the formula. If no coefficient is written, it is understood to be one.
Page : 2 Law 2 of Conservation of Matter 4 Hydrogen atoms here Example: 2H 2 + O 2 C o e f f i c i e n t S u b s c r i p t Oxygen atoms S u b s c r i p t C o e f f i c i e n t 2H 2 O S u b s c r i p t Oxygen atoms 4 Hydrogen atoms here 2 Hydrogens atoms and 2 Oxygen atoms on both sides means that the equation is balanced. This supports the law of conservation of matter.
7-5.9 Compare physical properties of matter (including melting or boiling point, density, and color) to the chemical property of reactivity with a certain substance (including the ability to burn or rust).
Page : Physical or Chemical Properties Physical Physical and chemical properties can be used to identify substances. Physical properties can be observed and measured without changing the kind of matter being studied.
Page : Physical or Chemical Properties Physical The following physical properties can be used to help identify a substance: o melting point o boiling point o density o color
Page : Physical or Chemical Properties Physical Melting Point o The temperature at which a solid can change to a liquid is its melting point. o The temperature at which a pure substance melts is unchanging under constant conditions.
Page : Physical or Chemical Properties Physical Melting Point o The melting point of a pure substance can be used to identify a substance. o Ice melts to form liquid water at 0 degrees C and 32 degrees F.
Page : Physical or Chemical Properties Physical Boiling Point o The temperature at which a liquid boils is the boiling point. o This is when a liquid changes into a gas. o First, bubbles form. The bubbles then grow larger. Finally, the bubbles rise to the surface and burst.
Page : Physical or Chemical Properties Physical Boiling Point o As long as the substance is boiling, the temperature of that substance remains constant (at its boiling point). o Boiling point is unchanging, so it can be used as a physical property to identify a substance. o The boiling point for pure water at sea level is 100 degrees C or 212 degrees F.
Page : Physical or Chemical Properties Physical Density o Density is a property that describes the relationship between the mass of a material and its volume. o Substances that are denser contain more matter in a given volume.
Page : Physical or Chemical Properties Physical Density o The density of a substance will stay the same no matter how large or small the sample. o Density can be used as a physical property to identify a substance. o EX: Lead is a very heavy, dense metal. The density of lead is much greater than the density of the very light metal, aluminum.
Page : Physical or Chemical Properties Physical Color o Color can be used to help identify a substance. o It must be used with other properties. Color alone can t identify a substance. o Absence of color is also a physical property.
Page : Physical or Chemical Properties Chemical Chemical properties can also be used to help identify a substance. Chemical properties can be recognized only when substances react or do not react chemically with one another. (a change in composition) A chemical property of one substance usually involves its ability to react (combine) or not react with another specific substance.
Page : Physical or Chemical Properties Chemical Two examples of chemical properties: o The ability to burn o The ability to rust
Page : Physical or Chemical Properties Chemical Two examples of chemical properties: o The ability to burn The ability of a substance to burn is a chemical property that involves a substance reacting quickly with oxygen to produce light and heat. The process is called burning.
Page : Physical or Chemical Properties Chemical Two examples of chemical properties: o The ability to rust The ability of a substance to rust is a chemical property that involves a substance reacting slowly with oxygen. The process is called rusting.
7-5.9 Compare physical properties of matter (including melting or boiling point, density, and color) to the chemical property of reactivity with a certain substance (including the ability to burn or rust).
Page : Physical or Chemical Changes Physical and chemical changes affect substances in different ways. o Physical changes do not change the composition of a substance, only the physical properties. o Chemical changes result in the formation of one or more new substances with new chemical and physical properties.
Page : Physical or Chemical Changes Physical Changes include: o Change in state of matter o Change in size or shape
Page : Physical or Chemical Changes Physical Changes include: o Change in state of matter When a substance changes from one state of matter to another, the composition of the substance remains the same. EX: solid to liquid (melting ice cream) liquid to solid (hardening of melted wax) liquid to gas (evaporating of water from wet clothes)
Page : Physical or Chemical Changes Physical Changes include: o Change in state of matter EX: gas to solid (forming of frost from water vapor) solid to gas (dry ice or solid air freshners) solid to gas is called sublimation
Page : Physical or Chemical Changes Physical Changes include: o Change in size or shape When a substance changes changes in size or shape, its composition remains the same. EX: cutting, tearing dissolving, stretching, or wrinkling shredding paper, dissolving sugar in water, stretching a rubber band, wadding up a piece of paper, or denting a piece of metal
Page : Physical or Chemical Changes Chemical Changes include: o Color Change o Temperature Change o Formation of a Precipitate o Formation of a Gas
Page : Physical or Chemical Changes Chemical Changes include: o Color Change When a substance changes color, the chemical composition of the substance may have changed. For example: iron turns to a reddish-brown when it rusts clothes change color when bleach is added apples turn brown when they react with oxygen in the air marshmallows turn black when burned
Page : Physical or Chemical Changes Chemical Changes include: o Color Change It is possible to have a color change without a chemical change. For example, you can add food coloring to water. It is still water, so that is just a physical change.
Page : Physical or Chemical Changes Chemical Changes include: o Temperature Change When a substance is combined with another substance, there may be an increase or decrease in temperature. For example: when wood burns to ash and gases, the temperature increases.
Page : Physical or Chemical Changes Chemical Changes include: o Temperature Change It is possible to have a temperature change without it being a chemical change. For example, the sun warms water in a pond. That is a physical change. It is still water in a pond.
Page : Physical or Chemical Changes Chemical Changes include: o Formation of a Precipitate When two solutions are combined, they may form a solid substance. The solid substance is called a precipitate. The formation of a precipitate is an indication that a chemical change has occurred.
Page : Physical or Chemical Changes Chemical Changes include: o Formation of a Precipitate For example: when carbon dioxide is combined with aqueous calcium hydroxide (limewater), solid calcium carbonate (chalk) is formed as the precipitate. The precipitate may be in the form of very small particles, appearing as cloudiness in the solution or as a solid which settles to the bottom of the container.
Page : Physical or Chemical Changes Chemical Changes include: o Formation of a Gas When solid or liquid substances are combined, they may form gas bubbles. The formation of the gas may indicate that a chemical reaction has taken place.
Page : Physical or Chemical Changes Chemical Changes include: o Formation of a Gas For example: when vinegar is added to baking soda, it forms carbon dioxide bubbles. It is possible to form gas without a chemical change. For example: when water is heated to boiling.