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