taks objective 3 structure and properties of matter middle school science science taks need to know...

TAKS objective 3Structure and Properties of

Matter

Middle School ScienceScience TAKS Need to Know

TAKS Need to Know 1

Atomic Theory

Atoms are building blocks of elements

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)

Two or more different atoms bond in simple ratios to form compounds (Ex: Hydrogen & oxygen can chemically

combine to form water- H2O )

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Atoms and Elements

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Atomic Particle Charges

Protons Positive +Neutrons Neutral =Electrons Negative -

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Location of Subatomic Particles

10-13 cm electrons

protons

neutrons

10-8 cm

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nucleus

Location of Atomic Particles

Inside the Nucleus

Protons with a Positive charge

ANDNeutrons 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???

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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!!!!

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1111

NaNa

22.9922.99

Atomic Mass on the Periodic Table

1111

NaNa22.9922.99

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Atomic Numberor Protons

Symbol

Atomic Mass orProtons + neutrons

Atomic Number

Atomic number = # of Protons

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Mass Number

The number of

protons and neutronsin an atom

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Number of Electrons

A balanced atom is neutral The net overall charge is zeroNumber of protons = Number of electronsAtomic number = Number of electrons

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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.

Metals & Nonmetals

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ElementElement ProtoProtonsns

NeutronNeutronss

ElectronElectrons s

2 elements 2 elements with with similar similar propertiesproperties

Chlorine-35 1717 1818 1717 F and BrF and Br

Iron-56

Magnesium-24

Lead-208

Nitrogen-14

26 30 26 Ru and Os

12 1212 Ca and Sr

82 82126

7 7 7

Sn and Ge

P and As

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Specific HeatMeasure 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 1o C in temperature.

Heat is measured in calories.

A calorie is the amount of heat needed to make 1 g of water rise 1o 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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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.

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Most metals have low specific heats, while nonmetal compounds & mixtures such as water, wood, soil, & air have relatively high specific heats.

How the Specific Heat of Water affects the Earth

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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.

Molecules & Compounds

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Mixtures

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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.

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Properties of MatterPhysical properties – can be observed without changing the substance into a different substance.

Chemical Properties

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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.

Chemical Reactions

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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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Chemical Equations

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