Matter Pure Substances Mixtures Elements Compounds Homogeneous Heterogeneous
Mixtures and Pure Substances Matter that consists of two or more substances mixed together but not chemically combined is called a mixture. A pure substance is made of only one kind of material and has definite properties.
Elements Elements are the simplest pure substance. –Examples: hydrogen, carbon, and oxygen. The smallest particle of an element that has the properties of that element is called an atom.
Compounds A molecule is formed when two or more atoms combine. Compounds are pure substances that are made of more than one element bound together. –Examples: water, table salt, and carbon dioxide.
MIXTURES Heterogeneous vs. Homogeneous Homogeneous matter: matter that has identical properties throughout. –Examples: Sugar, salt, water, and whipped cream Heterogeneous matter: matter that has parts with different properties. –Examples: granite, soil, potpourri
Conservation Law of Conservation of Matter (Mass): matter cannot be created or destroyed. Law of Conservation of Energy: Energy cannot be created or destroyed; it may only change from one form to another.
Matter and energy MUST be conserved; it’s the LAW!
Virtually everything that is, is made up of atoms.
We are all made of atoms…and only atoms. This includes you and me!
Making stuff nature never dreamed of. The Elements Song Currently we have about 118 kinds of atoms. In the natural world there exists 91 different kinds of atoms. The others have been artificially produced in laboratories.
We call each kind of atom an element, and give it a specific name and symbol. Copper Cu Gold Au
Atoms are made up of protons, neutrons, and electrons. Protons and neutrons are found in the nucleus of atoms -- roughly at the center Electrons travel around the nucleus. Of course real atoms don’t look anything like this!
Different kinds of atoms, or elements, are different because they have different numbers of protons. They don’t look anything like this either!
We list the elements by their atomic numbers - the number of protons they have. Hydrogen, number 1 Helium, number 2
Physical Properties Physical properties: characteristics that can be observed without changing the identity of the substance. Examples: –mass –volume –color –shape –texture –density
Physical Changes Physical change: a change in the physical form or properties of a substance that occurs without a change in composition. Examples: –melting –freezing –grinding –dissolving
Chemical Properties Chemical property: describes a substance’s ability to change into a different substance. Examples: –flammability –reactivity
Chemical Changes Chemical change: occurs when a substance changes composition by forming one or more new substances. (bonds are broken and bonds are formed) Example: –HCl + NaOH NaCl + H 2 O
Indications of a Chemical Change… Flames Gas is given off (not to be confused with boiling) Color Change