Matter and its Changes
Jan 25, 2016
Matter and its Changes
Atoms
• Matter is made up of atoms
• Matter is anything that takes up space and has mass
• Atoms are the “building blocks” of life
• Forms of matter that contain only one type of atom are called elements
• Atoms combine to form many different types of matter
Structure of an Atom
ProtonElectron (electron cloud)
Neutron
Mass Number =
Protons + Neutrons
Atomic Number =
Number of protons
Isotopes
• When the number of protons in an atom changes it becomes a different element
• Atom is electrically neutral when there are more neutrons than protons
• Atoms of the same element that have a different number of neutrons are called isotopes
• Ex. C12 = 6p +6n C14 = 6p + 8n
Ions
• Electrically charged atoms are called Ions• The number of protons is not equal to the
number of electrons• Ions are attracted to each other when they have
opposite charges
• Ex. Na+ + Cl- = NaCl = salt• Ex. Na+ + F- = Sodium Fluoride for
toothpaste
Combinations of Atoms
• Atoms combine by sharing their outermost electrons in their electron clouds
• When two atoms are combined a molecule is formed
Bonds
• Ionic Bond – Positive and Negative ions combine and electrons are transferred– Ex. NaCl
• Covalent Bond – Electrons are shared– Ex. H2O
Combinations of Atoms
How Atoms Combine
• When at least two atoms are combined a molecule is formed
• There are two ways in which atoms combine to form molecules and compounds
Ionic Bonding
• Positive and Negative ions combine and electrons are transferred
• Example: Na+ and Cl- = NaCl
Covalent Bonding
• In covalent bonding electrons are shared
• Example: 2H + O = H2O
Compound
A type of matter that has properties different from the properties of each of the elements in it
• Example: Na (metal) + Cl (gas) = NaCl (solid salt)
• Example: 2H (gas) + O (gas) = H2O (liquid water)
Mixture
• Many different substances that when mixed together, each substance retains its own properties
• Examples: sand, air and salad
Solution
• When one substance of a mixture is dissolved in another substance it is a solution
• Examples: tea w/ sugar, salt water
• Chemical properties describe how one substance changes when it reacts with another
• Examples: iron and oxygen = rust
• Physical Properties can be observed or measured without changing the substance
• Examples: color, shape, size, density and texture
Density
What is density?
• The measure of the mass of an object divided by its volume.
4. Liquid to a solid: freezing point
5. Solid to a liquid: boiling point
6. Only substance that occurs naturally as a solid, liquid, and gas: Water
Matter can change by:
1. Increasing or decreasing the temperature
Ex: freezing water turns it to a solid (ice)
2. Increasing or decreasing pressure
Ex: Pressure to ice cube changes it to liquid
Energy from Atoms
1. What is nuclear energy?
- Alternate energy source produced from atomic reactions
2. How fission produces nuclear energy:
- Splitting the nucleus of atoms in heavy elements
3. Most commonly used fuel in nuclear power plants:
- Uranium 235
Where is it found?
- Sandstones in the Rocky Mountains
4. Major source of nuclear waste: - Radioactive material
Most common method of storing nuclear waste:
- Power plants
Can remain active for 10,000 years
Two advantages to storing nuclear waste at Yucca Mountain:
1. Remote area (deserted)
1. Water table is far below storage facility
Two disadvantages to storing nuclear waste at Yucca Mountain:
1. Earthquakes could destroy storage facility
2. Large amount of nuclear waste in one area