Energy Transformations Georgia High School Graduation Test: Science Review

Radiation Radiation comes from the nucleus of an atom. Unstable nucleus emits a particle or energy  alpha  beta  gamma

Sample Question 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 from the nucleus 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

Transmutation The changing of one element to another is called transmutation This occurs whenever there is an alpha decay or a beta decay Remember, that for a gamma decay, the nucleus just changes internal energy levels, but doesn’t change the identity of nucleons

Radioactive 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 ALPHA DECAY BETA DECAY GAMMA DECAY

Half-Life The time it takes for half of the radioactive particles in a radioactive nucleus to decay One-half of that one-half will decay in the next half life One-half of that one-fourth will decay in the next half life

Half-Life

Sample Question Calculate the amount of radioactive substance that will remain after one half-life.

Half-life 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

Heat and Temperature In order to understand the nature of heat and temperature, it is necessary to appreciate the fact that matter consists of moving particles (atoms or molecules) which can interact with one another.

Heat and Temperature The motion of the particles is increased by raising the temperature. The motion of the particles is reduced by lowering the temperature.

Sample Question What is the effect of an increase in temperature on the motion of atoms? Ans: the motion of the atoms will increase

Temperature a measure of the average kinetic energy of molecules the higher the temperature, the faster the molecules

Sample Question Compare solids, liquids, and gases in terms of shape, volume, and movement of particles.

Phases of Matter STATE OF MATTER SHAPE VOLUME PARTICLE DESCRIPTION SOLID has definite shape has definite volume particles move slowly and cannot be compressed LIQUID has no definite shape (takes the shape of container) particles move faster but cannot be compressed GAS has no definite shape has no definite volume (fills volume of container) particles move the fastest and can be compressed

Phase Changes of Water

Phase Change Diagram of Water

Sample Question What is the effect of temperature change on the phases of matter?

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

Flow of Heat & Equlibrium Remember that Energy is Conserved, so if 1 substance loses heat the other gains heat. Thermal Equilibrium Heat will flow from a hot object to a cold object until they are at the same temperature.

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

Conduction Transfer of heat by direct contact of molecules. Molecules collide and transfer kinetic energy Can occur in all 3 states of matter Occurs the best in solids because they are more dense

Conduction Transfers heat until Thermal equilibrium is reached. Both substances reach the same temperature.

Convection Transfer of heat in fluids (gases & liquids) through currents. Convection is the movement of gases or liquids from a cooler spot to a warmer spot The hotter fluid tends to be less dense and therefore rise pushing cooler more dense fluid to the bottom causing what are called convection currents.

Ways heat can be transferred Radiation Transfer of heat in waves Does not require matter Types Electromagetic radiation (objects give off heat)

Sample Question 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 Ans: potential energy = stored energy due to position or chemical composition kinetic energy = energy due to motion

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.

Energy Sources SOURCE DEFINITION EXAMPLES chemical heat light 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 light energy 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

7. Question Describe the different forms of energy transformations when turning on a light switch. Ans: Electrical →heat →light

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.

Figure Reference Radioactive Decay figures: retrieved from http://library.thinkquest.org/3471/radiation_types_body.html Phase Changes of Water figure: retrieved from http://www.unc.edu/courses/2003ss2/geog/011/001/Phase_change.jpg Phase Change Diagram of Water figure: retrieved from http://www.st-ansgar.k12.ia.us/SCHWIESOW/Science/Physics/notes/images/phasediagram.gif Conversion of Energy figure: retrieved from http://www.physicsclassroom.com/Class/energy/U5L2bb.html