1 STAAR Structure and Properties of Matter Middle School Science

TAKS Need to Know2 Atomic Theory Atoms are building blocks of elements Atoms are building blocks of elements Atoms in each unique element are the same. (Ex: Every oxygen element has the same # of protons) Atoms in each unique element are the same. (Ex: Every oxygen element has the same # of protons) Atoms are different from atoms of other elements (Ex: Hydrogen has a different # of protons than oxygen) Atoms are different from atoms of other elements (Ex: Hydrogen has a different # of protons than oxygen) Two or more different atoms bond in simple ratios to form compounds (Ex: Hydrogen & oxygen can chemically combine to form water- H 2 O ) Two or more different atoms bond in simple ratios to form compounds (Ex: Hydrogen & oxygen can chemically combine to form water- H 2 O )

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5 Atoms and Elements

TAKS Need to Know6 Atomic Particle Charges Protons Positive + Neutrons Neutral = Electrons Negative -

TAKS Need to Know7 Location of Subatomic Particles cm cm electrons electrons protons protons neutrons neutrons cm cm nucleus

TAKS Need to Know8 Location of Atomic Particles Inside the Nucleus Protons with a Positive charge AND Neutrons with a Neutral charge –that means they do not have a charge Outside the Nucleus- in electron cloud Electrons with a Negative charge Did you know electrons are very, very small and move very, very fast???

TAKS Need to Know9 Periodic Squares The periodic square for an element can tell you lots of information about that atom. Atomic number = # of protons Atomic number = # of electrons That means in a neutral (uncharged) atom the # of protons and electrons are always the SAME!!!! 11Na22.99

TAKS Need to Know10 Atomic Mass on the Periodic Table 11Na22.99 Atomic Number or Protons Symbol Atomic Mass or Protons + neutrons

TAKS Need to Know11 Atomic number Atomic number = Atomic number = # of Protons # of Protons

TAKS Need to Know12 Mass Number The number of protons and neutrons in an atom

TAKS Need to Know13 Number of Electrons A balanced atom is neutral A balanced atom is neutral The net overall charge is zero The net overall charge is zero Number of protons = Number of electrons Number of protons = Number of electrons Atomic number = Number of electrons Atomic number = Number of electrons

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TAKS Need to Know17 Elements with similar properties are placed in the same group in the periodic table. The stair-step line separates the elements into metals and nonmetals.

TAKS Need to Know18 Metals & Nonmetals

TAKS Need to Know19 ElementProtonsNeutronsElectrons 2 elements with similar properties Chlorine F and Br Iron-56 Magnesium-24 Lead-208 Nitrogen Ru and Os 12 Ca and Sr Sn and Ge P and As

TAKS Need to Know20 Specific Heat Measure of how much heat matter can absorb. It is a measure of how much heat energy it takes to make 1 gram of a substance rise 1 o C in temperature. Heat is measured in calories. A calorie is the amount of heat needed to make 1 g of water rise 1 o C in temperature. The higher a substance’s specific heat, the harder it is to increase its temperature (as with the cloth car seat). The opposite is also true: a substance with lower specific heat increases in temperature very easily (as with the metal car door).

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TAKS Need to Know22 If you want to keep the temperature of something from changing very much…build it out of a material that has a high specific heat. Most metals have low specific heats, while nonmetal compounds & mixtures such as water, wood, soil, & air have relatively high specific heats.

TAKS Need to Know23 How the specific heat of water affects the Earth Oceans cover about 2/3 of Earth’s surface. Water’s characteristic of retaining heat is important to our climate. It means that our climate stays much more stable than it would if there were less water on Earth.

TAKS Need to Know24 Molecules & Compounds

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TAKS Need to Know26 Mixtures Combination of two or more pure substances. Substances are mixed together but have not reacted to form any new molecules. Example- Sugar (a compound) dissolves in water (a compound) to form a mixture. The molecules of sugar and water do not change chemically. They just become mixed together.

TAKS Need to Know27 Properties of matter Physical properties – can be observed without changing the substance into a different substance.

TAKS Need to Know28 Chemical Properties Characteristics of a substance that are observed when it reacts (changes) to produce one or more different substances. Example- Water can be changed into hydrogen gas and oxygen gas using an electric current. When water molecules change chemically into hydrogen gas and oxygen gas, we say that a chemical change has occurred. Hydrogen gas and oxygen gas each have a different set of properties. Substances change into different substances through chemical reactions.

TAKS Need to Know29 Chemical Reactions Substances change into other substances in chemical reactions. The atoms in the original substance are rearranged. The bonds in the original substance may be broken and new bonds may be formed between different atoms. This produces one or more new substances that may be either pure elements or compounds. The products of a chemical reaction always have difference chemical and physical properties than the original substance(s).

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TAKS Need to Know32 Chemical Equations

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