STANDARD 3a Students know the structure of the atom and know it is composed of protons, neutrons, and electrons

Structure of Matter All matter is made up of small particles called atoms An atom is the smallest unit of an element Composed of three particles –Protons – positively charged particles in the nucleus (center) –Neutrons – particles with no charge located in the nucleus –Electrons – negatively charged particles surrounding the nucleus in shells also known as energy levels Most of the atom’s mass is located in the nucleus

Structure of Matter 18. Which of the following best describes an atom? A Protons and electrons grouped together in a random pattern B Protons and electrons grouped together in an alternating pattern C A core of protons and neutrons surrounded by electrons D A core of electrons and neutrons surrounded by protons ANSWER: C

Structure of Matter 20. The diagram above shows models of two different atoms. Which subatomic particles are represented by the black dots? Aprotons Bneutrons Celectrons Dnuclei ANSWER: C

Structure of Matter 22. Which particles in an atom account for nearly all the atom’s mass Aelectrons only Bprotons only Cneutrons only Dprotons and neutrons ANSWER: D

STANDARD 3b Students know that compounds are formed by combining two or more different elements and that compounds have properties that are different from their constituent elements

COMPOUNDS All matter is made of elements In nature, most elements are found combined with other elements because most atoms are unstable When atoms combine, they form a chemical bond, which is a force of attraction between two atoms A compound is a substance made of two or more elements chemically combined in a set ratio. Water molecule is always made up of two hydrogen atoms to one oxygen atom.

COMPOUNDS Valence electrons are the electrons that have the highest energy level and are held most loosely because they are farthest away from the nucleus Atoms become stable (or happy) when they have a total of 8 valence electrons. All atoms except the noble gas atoms have fewer than 8 valence electrons Atoms achieve 8 valence electrons by bonding with other atoms Two main types of chemical bonds: ionic bonds and covalent bonds An ion is an atom or group of atoms that has an electric charge: positive or negative

COMPOUNDS Ionic Bond: a chemical bond that forms as a result of the attraction between positive and negative ions Covalent Bond: a chemical bond that forms when two atoms share valence electrons A molecule is a neutral group of two or more atoms joined by covalent bonds Water is a molecular compound with a chemical formula of H 2 O

COMPOUNDS 24. Which of the following chemical formulas represents a compound? AHe BO2BO2 CHCl DSn ANSWER: C

COMPOUNDS 26. The atoms in a molecule of water are joined by Aionic bonds Bcovalent bonds Cunshared electrons Dshared protons ANSWER: B

COMPOUNDS 27. Magnesium reacts with oxygen to form MgO. Properties of MgO are most likely Asimilar to magnesium Bsimilar to oxygen Cdifferent from magnesium or oxygen Dsimilar to both magnesium and oxygen ANSWER: C

STANDARD 3c Students know atoms and molecules form solids by building up repeating patterns, such as the crystal structure of NaCl or long- chain polymers

STRUCTURE OF COMPOUNDS Ionic compounds form solids by building up repeating patterns of ions. The result is a solid with an orderly, three dimensional arrangement called a crystal Solid ionic compounds are hard and brittle, have high melting points and when melted or dissolved conduct electricity

STRUCTURE OF COMPOUNDS Molecular compounds contain atoms that are covalently bonded, forming molecules Molecular compounds have low melting and boiling points and do not conduct electricity

STRUCTURE OF COMPOUNDS Some molecular compounds are composed of polymers A polymer is a very large molecule made of a chain of many repeating, smaller molecules bonded together Many of the molecules that make up living things are polymers: proteins, DNA, carbohydrates Amino acidNucleotide Glucose

STRUCTURE OF COMPOUNDS 28. Which is not a characteristic of a molecular compound? Alow melting point Bdoes not conduct electric current Clow boiling point Dhard, brittle solids at room temperature ANSWER:D

STRUCTURE OF COMPOUNDS 29. What type of structure is shown in the diagram? Aatom Bcrystal Cmolecule Dpolymer ANSWER: B

STRUCTURE OF COMPOUNDS 30. Which of the following kinds of force helps hold the particles together? Aelectrical attraction Bmagnetic attraction Cgravitational attraction Dthermonuclear attraction ANSWER: A

STRUCTURE OF COMPOUNDS 31. Some compounds found in the human body are long chains of smaller molecules. These chains are called Acarbon molecules Bcovalent bonds Cpolymers Dcrystals

STANDARD 3d Students know the states of matter (solid, liquid, gas) depend on molecular motion

Molecular Motion 32. Which type of motion best represents the movement of gas particles? A Motion 1 B Motion 2 C Motion 3 D Motion 4 ANSWER: A

STANDARD 3e Students know that in solids the atoms are closely locked in position and can only vibrate; in liquids the atoms and molecules are more loosely connected and can collide with and move past one another; and in gases the atoms and molecules are free to move independently, colliding frequently

Molecular Motion Solid Liquid Liquid Gas Gas

Molecular Motion Definite shape and volume Lowest energy Tightly packed together Does not take the shape of its container Definite Definite volume but no definite shape Slightly Slightly higher energy than solids Molecules Molecules slide past one another Takes Takes the shape of its container No definite shape or volume Highest energy Molecules move throughout the container Takes shape of container SOLID LIQUID GAS

CHANGES OF STATE A change of state is the conversion of a substance from one physical form to another. All changes of state are physical changes. During a change of state, energy of a substance changes. Energy is either released or absorbed

CHANGES OF STATE Melting – from a solid to a liquid Freezing – from a liquid to a solid Vaporization – from a liquid to a gas –Boiling – takes place throughout the liquid –Evaporation – takes place only on the surface Condensation – from a gas to a liquid Sublimation – from a solid to a gas

CHANGES OF STATE

33. What occurs when liquid water becomes ice? AEnergy is added to the water, so its molecules move more slowly BEnergy is added to the water, so its molecules move more quickly CEnergy is removed from the water, so its molecules lock into place DEnergy is removed from the water, so its molecules move apart ANSWER: C

Changes of State 34. The graph shows the effect of adding energy to water at sea level. When the temperature reaches 100 degrees Celsius, what happens to the water molecules as energy continues to be added? A. The water molecules gain energy as the temperature continues to rise B The water molecules gain no energy and the temperature stays the same C The water molecules become more ordered as the state changes to a gas D The water molecules move farther apart as the state changes to a gas ANSWER: D

CHANGES OF STATE 35. The diagram illustrates the particles of a solid substance held in a container. What would happen if the substance gained enough energy so that it melted completely? AThe particles would remain locked together in the same shape BThe particles would spread out into a layer that fills the bottom part of the container CThe particles would spread apart widely and fill the entire container DThe particles would chemically change into new substances ANSWER: B