Matter and Its Changes

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Chapter 2

• Matter and Its Changes

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2.1 Atoms

• The Building Blocks of Matter
• Matter everything that takes up space and has
  mass
• Matter is made up of particles called atoms
• The structure of the atoms determines the
  characteristics of matter

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2.1 Contiued

• Atoms
• Are the building blocks of matter
• The arrangement and types of atoms give matter
  its properties

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2.1 Continued

• Elements
• Atoms combine together to form different types of
  matter
• Two or more atoms of the same type together forms
  elements

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2.1 Continued

• Models of the Structure of Atoms
• Atoms cant be seen with the naked eye
• Atoms can only be seen by an electron microscope

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2.1 Continued

• Protons and Neutrons
• Particles of atoms
• Proton positive particles found in the nucleus
• Neutrons neutral particles found in the nucleus

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2.1 Continued

• Nucleus central portion of an atom that
  contains the protons and neutrons
• Has an overall positive charge
• The positive charge in the nucleus is offset by
  the negative charges of the electrons

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2.1 Continued

• Electrons
• Negatively charged particles that orbit the
  nucleus
• The number of electrons always equals the number
  of protons
• Where the electrons orbit the nucleus is called
  the electron cloud

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2.1 Continued

• Mass Numbers and Atomic Numbers
• Mass number
• equal to the number of protons and neutrons in
  the nucleus of an atom
• Doesnt include the electrons, since electron
  mass is to small to be accounted for

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2.1 Continued

• Atomic number
• Always equals the number of protons in the
  nucleus
• Always equals the number of electrons in the
  electron cloud

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2.1 Continued

• Isotopes
• If you change the number of protons in an atom
  the a new element will be formed
• Can change the number of neutrons without making
  a new element

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2.1 Continued

• Definition atoms that have same number of
  protons and electrons, but have a different
  number of neutrons
• Uses medical purposes, dating fossils

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2.2 Combinations of Atoms

• How Atoms Combine
• Molecules and Compounds
• Molecule
• the combination of two or more atoms of elements
  by sharing electrons

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2.2 Continued

• Compounds
• Type of matter that has properties different fro
  the properties of each of the elements in it
• When atoms of elements combine, they can change
  their physical form

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2.2 Continued

• For example, hydrogen and oxygen are gases, but
  when combined they form a water molecule, which
  is a liquid

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2.2 Continued

• Chemical Properties
• Describes how one substance changes when it
  reacts with other substances
• For example iron reacts with water and oxygen
  and is converted to rust

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2.2 Continued

• Ions
• A positively or negatively charged atom
• Caused by losing or gaining electrons by sharing
  them with another atom

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2.2 Continued

• Mixtures
• A combination of different substances in which
  each of the components keeps its own physical and
  chemical properties despite being mixed

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2.2 Continued

• Solutions
• Are a type of mixture
• Definition when one or more parts of a mixture
  are dissolved by another
• Example salt water
• Molecules of the dissolved substance is evenly
  spread throughout the solution

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2.2 Continued

• Solute the substance that is dissolved
• Solvent the substance that does the dissolving

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2.2 Continued

• Separating Components of Mixtures and Compounds
• Use chemical changes
• Chemical change converts one substance into one
  or more new substances with different chemical
  properties

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2.2 Continued

• Exploring Matter
• Components of mixtures retain their own
  individual properties
• When atoms combine, they lose their own
  individual properties to form compounds

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2.3 Matter

• Physical Properties of Matter
• Physical properties
• Properties of matter that can be observed without
  changing the matter into a new substance
• Usually use your senses to observe physical
  properties

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2.3 Continued

• Density
• The measure of the mass of an object divided by
  its volume
• Usually measured in g/cm3
• Substances that float in water are less dense
  than water
• Substances the sink in water are more dense than
  water

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2.3 Continued

• States of Matter
• Four states of matter
• Solid
• Atoms of the molecules are in a fixed position
• The molecules may vibrate, but they dont move

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2.3 Continued

• Molecules are packed tightly together, which
  prevents them from changing places
• Molecules are strongly attracted to one another,
  which also prevents molecules from moving

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2.3 Continued

• Liquids
• Molecules are strongly attracted to each other,
  but not as strongly as solids
• Molecules remain close to one another, but are
  free to change positions with each other
• Allows liquids to flow

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2.3 Continued

• Molecules of liquids take on the shape of their
  container, but it resists changes in volume
• Gases
• Molecules have very little attraction to each
  other
• Molecules move freely and independently
• Molecules spread evenly within their container

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2.3 Continued

• Plasma
• Most matter in the universe is a plasma
• Composed of ions and electrons
• Most of the electrons have escaped the electron
  cloud

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2.3 Continued

• Changing the State of Matter
• Changes by substances reaching their freezing or
  boiling points
• Freezing
• Changes a substance from a liquid to a solid

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2.3 Continued

• Boiling
• Changes a substance from a liquid to a gas
• Water is the only substance that exists as a
  solid, liquid, and gas

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2.3 Continued

• Factors that determine the state of matter
• The attraction between atoms or molecules
• The rate of movement of atoms or molecules

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2.3 Continued

• Ways to change the state of matter
• Adding or decreasing thermal energy is the most
  common method to change the states of matter
• Increasing or decreasing the amount of pressure

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2.3 Continued

• Changes in Physical Properties
• The chemical properties of matter stays the same
  when the state of matter changes
• Most substances are more dense than when they are
  in their liquid state
• Exception is water

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2.3 Continued

• Classifying Matter
• Matter is classified by the state it is present
  in
• Can be changed by increasing or decreasing the
  thermal energy

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2.3 Continued

• Chemical properties remain the same, while
  physical properties change when substances change
  their state of matter

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2.4 Energy from Atoms

• Nuclear Energy
• Alternative energy produced from atomic reactions
• Energy is produced when atoms are split
• Heavy elements are split into lighter elements

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2.4 Continued

• Fission
• The splitting of nuclei of atoms in heavy
  elements such as uranium
• Most commonly used element is uranium-235

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2.4 Continued

• process
• Elements are mined and concentrated
• They are placed in metal pipes called fuel rods
• Fuel rods are placed in cooled water in a nuclear
  reactor

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2.4 Continued

• A control rod is removed and the nuclei of the
  uranium begin to split and release heat
• This produces steam and the steam turns a turbine
• The turbine turns a generator to produce
  electricity

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2.4 Continued

• Storing Nuclear Waste in Yucca Mountain
• The waste is highly radioactive
• Waste can remain radioactive for thousands of
  years
• One possible place is Yucca Mountain in Nevada

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2.4 Continued

• Concerns about Yucca Mountain
• Earthquakes, volcanoes, groundwater
• Reasons for a good place
• Very little rainfall
• Very low water table
• Earthquakes will not affect deeply buried wastes

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2.4 Continued

• Search for Other Locations
• Trench 14 in Nevada
• Formed by limestone deposits
• Could have formed from percolating water or
  uprising of water from the water table

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2.4 Continued

• Good site if it is formed by percolating water,
  since it would seal the waste from the water
  table
• Bad site if it is formed by uprising water, since
  it would release the waste to the environment

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2.4 Continued

• Concerned about the numerous faults in the area