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Chapter 2 Introduction. What is matter? What isn’t ? Matter: Solids, liquids, gases, plasma Non-matter: light, energy, forces. Think Pair Share. What are Earth materials and why are they important to us ? Rocks, metals/ores, water, etc. Objectives.
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Chapter 2 Introduction • What is matter? What isn’t? • Matter: Solids, liquids, gases, plasma • Non-matter: light, energy, forces
Think Pair Share • What are Earth materials and why are they important to us? • Rocks, metals/ores, water, etc.
Objectives • Relate atomic and molecular structure to the traits of matter. • Understand the states of matter (solid, liquid, gas, plasma) and how matter cycles over time. • Identify the major elements of the Earth’s crust.
“Building Blocks” of Matter • Element: a substance that is made of only one type of atom and cannot be broken down into simpler substances by normal physical or chemical processes.
Atomic Structure • Atom: the smallest particle of an element that has all of it’s characteristics
Atomic Structure • Atoms are made of combinations of protons (+) and neutrons in the nucleus and electrons (-) orbiting around the nucleus. • Electrons have very little mass.
Atomic Structure • Atomic Number: the number of protons in the nucleus.
Atomic Structure • Mass Number: the number of protons and neutrons of a specific isotope. • Isotopes have the same number of protons, but different numbers of neutrons Mass Number = (Number of Protons) + (Number of Neutrons)
Atomic Structure • Atomic Mass: the weighted average Mass Numbers of all the isotopes
Combining Elements • Some elements are quite content to remain alone, but most will attempt to combine with other elements to form the various the common objects and substances we see every day. + = Table salt Sodium Metal Chlorine gas
Combining Elements • A compound is a substance that is composed of two or more elements that are chemically combined. • Water (H2O) is a compound.
Combining Elements • Some elements form bonds when this electron exchange takes place • Covalent bonds form when atoms share electrons, such as H2O. • Ionic bonds form when electrons are exchanged, creating charged atomscalled ions. Table salt (NaCl) is an example.
Combining Elements • NaCl is an example of ionic bonding.
Metallic bonds • Metallicbonds are strong and found in metals, such as copper. Electrons are free to move from one positive ion to another. Flowing electrons = conduction of electric current and heat • Metallic bonding gives metals special properties that make metals valuable as Earth resources. Metals may be mixed into minerals/rocks. Minerals which contain metals are called ores.
Mixtures • Mixtures occur when compounds and elements mix together but do NOT combine chemically. Mixtures can be physically separated. • The mixture is heterogeneous if each component of mixture retains its own properties. EXAMPLE: oil and water
Homogeneous mixtures • Homogeneous mixtures are also known as solutions. The properties of the components may be different from the properties of the mixture. EXAMPLE: salt and water (a liquid solution formed when salt dissolves in water)
Density • Density is a property of matter. • Density: A measure of the mass of an object divided by its volume. The unit of measure is frequently g/mL or g/cm3. • Most materials become less dense from as state changes from solid->liquid->gas. Water is an exception… ICE FLOATS! • Less dense materials float on denser materials.
