How Do We Make New STUFF From Old Stuff? Chalk Calcium Carbonate CaCO3 Comparing Chalk Characteristics Same Different Size Hardness Malleability Weight Mass Color Texture Shape Use the chart to compare A, B and C. Matter can be divided into to broad categories: Pure Substances and Mixtures Pure Substance A pure substance is composed of one type of atom or molecule. – Elements are substances that are made up of a single type of atom. – Molecules are substances that are formed when two or more atoms join together chemically. – Compounds are molecules that contain at least two different elements. NOTE: All compounds are molecules but not all molecules are compounds. Elements Elements are pure substances because they are each made up of one type of atom. An element is uniform all the way through. Over 100 elements are organized on the periodic table of elements. Elements cannot be broken into simpler parts EXCEPT during nuclear reactions. Molecules Molecules are substances that are formed when two or more like or unlike atoms join together chemically. Compounds Compounds are molecules that contain at least two different elements which are combined chemically in some way. Compounds cannot be separated by physical means. Separating a compound requires a chemical reaction. Which one represents a PURE SUBSTANCE? Mixture A mixture is composed of different types of atoms or molecules that are not chemically combined. The substances in a mixture do not chemically react with one another. Mixtures can be separated by both physical and chemical means. There are two types of mixtures: Homogeneous mixtures Heterogeneous mixtures Homogeneous Mixtures A homogeneous mixture is a type of mixture in which the composition is uniform and every part of the solution has the same properties. Homogeneous mixtures are also called solutions. CuCl2 + H20 Heterogeneous Mixtures A heterogeneous mixture is a mixture of two or more chemical substances that remain physically separate. Different regions of a heterogeneous mixture have different properties. Chalk Calcium Carbonate CaCO3 Comparing Chalk Characteristics Same Different x Size Hardness x Malleability x Weight x Mass x Color x Texture x Shape x Properties • Properties are characteristics of substances that scientists use to describe substances, to help identify substances, and to distinguish substances from each other. • The properties of a substance stay the same regardless of the substance’s shape or size. – Examples of properties include color, hardness, density, and melting point. – Non-examples of properties include mass, volume, weight, shape Molecule Choose a food item. State whether the item is a pure substance or a mixture. Support your claim with evidence and reasoning.