Post on 30-Dec-2015
Introduction
• From the key vocabulary, circle the words that you can already define or use in a sentence.
• Write down two or three things that you think are important for you to know today.
Sample Question
1.Describe the process of radioactive decay in which the unstable nucleus of a radioactive isotope spontaneously decays.
Radioactivity
•the spontaneous process that occurs when an unstable nucleus releases particles and/or energy to form a more stable nucleus
Radioisotopes
• unstable radioactive nucleus• examples:
•carbon-14•deuterium (hydrogen with 1 neutron)
•all elements with atomic numbers above 83
Radioactive Decay
ALPHA DECAY
BETA DECAY GAMMA DECAY
•radioactive decay = the release of subatomic particles by radioactive isotopes
•alpha and beta decay result in transformed atom
•gamma decay results in same atom with release of energy
Sample Question
2.Calculate the amount of radioactive substance that will remain after one half-life.
Half-life
• the time it takes for half of the radioactive particles in a radioactive nucleus to decay
• example:• If an original sample of carbon-14 has
a mass of 10 grams and its half-life is 5700 years, how many grams of carbon-14 would remain after one half-life?• ANSWER: 5 grams
Temperature
•a measure of the average kinetic energy of molecules
•the higher the temperature, the faster the molecules
Sample Question
4.Compare solids, liquids, and gases in terms of shape, volume, and movement of particles.
Phases of MatterSTATE OF MATTER
SHAPE VOLUMEPARTICLE
DESCRIPTION
SOLIDhas definite
shapehas definite
volume
particles move slowly and cannot be
compressed
LIQUID
has no definite shape (takes the
shape of container)
has definite volume
particles move faster but cannot be
compressed
GAShas no definite
shape
has no definite volume (fills volume of container)
particles move the fastest and
can be compressed
Phase Changes
• to increase the temperature of a substance energy must be absorbed by that substance
• to decrease the temperature of a substance energy must be released by that substance
Sample Question
6. Give examples and describe the two forms of energy encountered in a system between any of the following: chemical, heat, light, electrical, and mechanical.
Types of Energy
• potential energy = stored energy due to position or chemical composition
• kinetic energy = energy due to motion
Energy SourcesSOURCE DEFINITION EXAMPLES
chemical energy stored in chemical bonds, food, or fuel
cause of burning gas, energy from food
heat total amount of energy of atoms of matter
boiling water, heat
from burning gas
lightenergy that travels in waves and moves through empty
space
any electromagnetic wave (radio, visible, UV, x-rays, gamma)
electrical energy due to the motion of charges
current electricity
mechanical energy acquired or released by moving objects
falling rock, swinging a baseball bat, sound
Heat Energy
• Heat can be transferred through:• Conduction = when objects touch• Convection = when matter moves• Radiation = in the form of waves (does not
require matter)• Conductors = easily transmit energy
• Example: metals• Insulators = do not easily transmit
energy• Example: gases such as air
Conversion of Energy
• The sum of KE and PE is constant if there is no friction.
• Realistically, some energy is transferred to heat due to the friction between the wheels and the track.
Discussion
• The molecular theory of molecules states that the velocity of molecules correlates to the temperature of the system. How are the actions of a group of people affected by the temperature of a room? How are those actions similar to and different from atoms at the same temperature?
Lesson Summarized
• Write a sentence that explains the system discussed.
• Draw a graphic organizer that shows the relationship of the parts to the whole.
Short Quiz Answers
1. Half-time is the time it takes for half of the radioactive particles in a radioactive nucleus to decay.
2. All isotopes have the same atomic number but different atomic masses.
3. Some isotopes are radioactive due to the different number of neutrons.
4. See the table on sources of energy.5. Ice, water, and steam all have the same
chemical composition (H2O) but each are in a different phase.