TAKS Objective 4 Matter and Change
All matter has mass and takes up space, yet matter can exist in different states. • There are three main states of matter • 1. Solid • 2. Liquid • 3. Gas
Solids • Every solid has a definite volume and a definite shape. • The particles are tightly compressed.
Liquids • A liquid flows and takes the shape of its container. • Liquid matter has a definite volume but no definite shape.
Gases • Gases expand or contract to fill the space available to them. They can also compress to fill smaller spaces. • A gas has neither a definite shape or a definite volume.
Size and shape do not change an object’s density. • Example: a candle’s density is determined, then you melt the wax. What is the melted wax’s density? The same as the candle that was not melted.
The density of solids usually decreases slightly as temperature increases because solids expand when heated. • Ice is less dense than water. Because of this, the ice floats in water.
The formula for density is: d=m/v And this line means to divide M Remember… this line means to multiply D V
A block of maple wood with a volume of 405 cubic centimeters and a density of 0.67 g/cm3 is sawed in half. The density of the two smaller blocks is now — A one-fourth the original density B one-half the original density C two times the original density D the same as the original density
A sample of an element has a volume of 78.0 mL and a density of 1.85 g/mL. What is the mass in grams of the sample? Record and bubble in your answer to the nearest tenth on the answer document. Use the formula page, D = m/v…now set up in a triangle… ? 1.85 78.0 and solve…1.85 X 78.0 = 144.3
Buoyancy • Buoyancy is a measure of the upward pressure a fluid exerts on an object.
Buoyant Force • If the buoyant force is greater than its weight, the object floats. • If the buoyant force is less than its weight, then the object will sink. HELP! I am drowning because the buoyant force is less than my body weight!!!
Viscosity • Viscosity is the measure of a material’s resistance to flow. • High-viscosity fluids take longer to pour from a container than low-viscosity fluids. • Example: High-viscosity = syrup Low-viscosity = water
Temperature Affects Viscosity • As the temperature of a liquid is raised, the viscosity decreases. • Example: warm hot fudge is much easier to pour than when it is cold
Atoms are. . . • The smallest part of a single element. • The basis of all matter. • Made of mostly empty space. • Have a positive core or nucleus. • Have electrons orbiting in clouds.
Parts of an Atom • Protons • Located inside the nucleus • Have a positive charge • Neutrons • Located in the nucleus • Have a neutral charge or no charge • Electrons • Orbit around the nucleus • Have a negative charge
Atomic Number • The atomic number is the number of protons in the element’s nucleus. • Every atom of the same element has the same atomic number. • Ex: Every carbon atom has 6 protons • The number of electrons in an atom equals the number of protons in that atom. I see…the atomic number is like a person’s DNA…it’s what identifies us.
When the atom has equal numbers of protons and electrons it is said to be electrically neutral. • This is because the positive charges equal the negative charges, therefore, there is no charge.
Mass Number or Atomic Mass • The mass number is the sum of the number of protons and neutrons in the nucleus • Number of neutrons = mass number – atomic number
Isotopes • Atoms of the same element that have different numbers of neutrons are called isotopes • To determine the number of neutrons in an isotope: • Mass number – Number of protons = Number of neutrons
4 Basic Types of Elements • Metals: found to the left of the stair-step line • Non-metals: found on the right side of the stair-step line • Metalloids: found along the stair-step line • Synthetic: made in the laboratory and not yet found in nature – many of the Actinide and Lanthanide series and very large # elements.
Where are the metal elements? Left of the Stair-step line!
Properties of Metals • Metals are: • Conductors • Lustrous (shiny) • Electron donors • Malleable (rolled into sheets – Aluminum foil) • Ductile (pulled into wires)
Where are the nonmetals? To the Right of the stair step line, and Hydrogen!
Properties of Nonmetals • Nonmetals are brittle, insulators, electron acceptors • Usually form negative ions (except H) • Many are gases at room temperature • Found to the right of the stair-step line
According to the periodic table, which element most readily accepts electrons? • A Fluorine • B Nitrogen • C Arsenic • D Aluminum Fluorine only needs 1 electron to complete its shell of 8, so it will accept it from any other element very very very easily. This periodic property increases as you move up and left in the table, except for the Noble Gases.
Use the Table provided! What do the numbers mean? This is the atomic number. It is the number of protons in a single atom of this element. By the way, its also # of electrons. 11 Na The symbol for this element. This is the atomic mass, it is the number of protons + neutrons, or the mass of the nucleus of an atom. 22.990 sodium This is the name of the element.
Transition Elements • The transition elements are located in groups 3-12 of the periodic table. • These elements are very hard, with high melting points and boiling points.
Alkali Metals • The alkali metals, found in group 1 of the periodic table are very reactive metals. • They have only one electron in their outer shell. Therefore, they are ready to lose that one electron in ionic bonding with other elements.
Alkaline Earth Metals • The alkaline earth elements are metallic elements found in the second group of the periodic table. • All alkaline earth elements have an oxidation number of +2, making them very reactive.
Halogens • The halogens are five non-metallic elements found in group 17 of the periodic table. • All halogens have 7 electrons in their outer shells, giving them an oxidation number of -1. • The halogens exist, at room temperature, in all three states of matter: • Solid- Iodine, Astatine • Liquid- Bromine • Gas- Fluorine, Chlorine
Noble Gases • The noble gases are found in group 18 of the periodic table. • All noble gases have the maximum number of electrons possible in their outer shell (2 for Helium, 8 for all others), making them the most stable.
Valence Electrons • Valence electrons are those electrons that an atom uses in forming a bond with another atom. • These electrons are found in the outermost shell of an element. • Look at your periodic table. You should see roman numerals with A’s beside them. These tell you the number of valence electrons.
Valence electrons • How many valence electrons does Calcium have? • How many valence electrons does Oxygen have? • How many valence electrons does Chlorine have? 2 6 7
Important Note!!!! • Atoms in the same group have similar chemical properties because they have the same number of valence electrons.