Chapter 2 Matter, Energy & Change W/ Concept Mapping
Chapter Objectives • TSW be able to apply the skill of concept mapping as a means of organizing the classification of matter system. • TSW have a solid understanding of how our universe is composed of different arrangements & combinations of the known 113 elements. • TSW be able to differentiate between physical and chemical properties and physical and chemical changes • TSW be able to distinguish between intensive and extensive properties • TSW be able to identify changes as endothermic or exothermic and display an understanding that energy is involved in all changes of matter.
Matter is… • By definition matter is anything that has mass and volume (or takes up space) • Since everything has mass and takes up space…everything we see and touch is composed of matter. • The “Building Blocks” of matter are atoms.
Mass vs. Weight • We use these terms interchangeably, however, they do have different meanings when used correctly. • Mass is defined as a measure of the amount of matter in a sample. • Weight is defined as a measure of the pull of gravity on a sample of matter. • Mass would remain constant anywhere in the universe, however, the weight would change.
Atoms • An atom is the smallest portion of an element that retains the unique properties of that element. • We will learn more about atoms in the next chapter.
Pure Substances • Are any materials with a fixed composition having definite set of physical and chemical properties • There two types of pure substances • Elements – unique arrangements of electrons, protons and neutrons that specific properties. • Compounds – two or more element chemically connected with definite composition and arrangements.
Examples • Elements: • Na – sodium • O2 – oxygen • Compounds: • MgCl2 – Magnesium Chloride • H2O – Water • H2O2 – Hydrogen Peroxide
Mixtures • Are materials with two or more pure substances mixed together but not chemically connected to one another. • There are two types of mixtures • Homogeneous – one phase with uniform distribution of particles • Heterogeneous – clusters of atoms with two or more phases and a non-uniform distribution of particles.
Properties of Matter • Every pure substance has a definite set of physical and chemical properties that exist even in the smallest sized sample. • We can use these properties to identify a pure substance.
Chemical Property • A Chemical Property is one that can only be observed during the course of a chemical change. • There are four tell tale signs that a chemical change is occurring… • A release of a gas • A change of color • A release or absorption of heat and/or light • Formation of a precipitate
A Precipitate? • A precipitate is a solid that is produced from two liquid reactants. • Example: Pb(NO3)2 + KI Yellow Precipitate
Examples of Chemical Properties • Flammability • Reactivity • Stability
Chemical Changes • A Change that results in a new substance that has a different arrangement of atoms with a set of chemical and physical properties different from the substance we started with.
A physical property is one which can be observed in the absence of a chemical change. Mass Density MP/BP Conductivity Color Malleability Physical State Physical Properties Every element, compound or molecule has a unique combination of these properties that allow us to use them in separating them from a mixture.
Intensive & Extensive • Some properties depend on the amount of the substance present and others do not… • An Intensive property is one that does not depend on the amount of substance present. • An Extensive property is one that is dependant on the amount of the substance present.
Density… • Density is one of the most useful intensive physical properties. • We can observe that each substance has its own unique value…thus we can determine the density of any unknown and use it to determine the substances identity. • The formula for density is D = mass / volume
Physical States of Matter • Solid – Sample of matter that has a definite volume and shape. • Liquid – Sample of matter that has a definite volume, but it adopts the shape of any container. • Gas – Sample of matter that has neither a definite shape nor definite volume. • Plasma – Sample of matter at high temperature where individual atoms lose their electrons.
Physical Changes • These are changes in the appearance of a substance, not in the identity of a sample of matter. • One example of this would be a change in the physical state that a sample of matter exists in. • Example: Ice (solid water) melting into liquid water.
Changes in State • You will see throughout the course that energy is involved in all changes, both chemical and physical changes • That means that changes in state are also displays of changes in energy.
More About Change • When a change occurs and energy is lost it is called exothermic…think of it this way: • Exo Exiting the system • When a change occurs and energy is absorbed it is called endothermic…think of it this way: • Endo Entering the system
Law of Conservation of Matter • States: • The amount of matter in the universe is constant • Matter cannot be created or destroyed only change form.