GED Physical Science

Heat

• Heat is the flow of energy from a cold object to a warmer one.

• Heat can be transferred by convection, conduction, or radiation

Transfer of heat

• Conduction- Transfer of heat through direct contact

• Convection- Heat transfer through hot particles rising and cool particles falling

• Radiation- Hot particles moving away from a reaction (like a fire).

Transfer of Heat

Heat in Reactions

• Endothermic reactions absorb heat from surroundings. Examples: melting ice, evaporating liquid

• Exothermic reactions give off heat. Examples: fire/combustion, condensation of liquids

Photo: University of Richmond

Potential and Kinetic Energy

• Kinetic energy is energy of motion

• When an object is in a high place it has potential energy because of gravity

• When it gains speed as it falls it converts potential energy to kinetic energy.

Chemical Energy

• Chemical energy is potential energy that could be converted to other types or energy by chemical reaction

• Chemical energy of food can be converted to kinetic energy (movement) by cells in the body

• Combustible materials contain chemical energy that is given off when they burn

Photo: TheDailyNathan

Mechanical Energy

• Sum of potential and kinetic energy

• Remains constant: potential energy is converted to kinetic energy and back.

Sources of Energy: The Sun

• Heat energy radiates from sun and is absorbed in solar panels

• Method of energy production that reduces pollution

• Sustainable, but reliant on sunlight

Sources of Energy: Fossil Fuels

• Oil, Coal and Natural Gas are mined or drilled and burnt, producing energy

• Fossil Fuels may not be sustainable because there is a finite amount

• Fossil fuels produce pollution

Sources of Energy: Nuclear

• Splitting an atom (nuclear fission) gives off heat in a reaction and the energy is harnessed

• Sustainable, but does produce some nuclear waste

• Threat of accidents (Chernobyl/Fukushima)

Waves

• Waves transfer energy• Electromagnetic waves

transfer energy by vibration of electric and magnetic fields

• Water waves transfer energy by moving particles of water

• Sound waves are movement of particles transmitting sound

Parts of a Wave

• Wavelength: Distance between waves

• Amplitude: Height of waves

• Frequency: How many waves occur in a time frame

• Higher wavelength means lower frequency.

image: Simon Baier

Electromagnetic Spectrum

Forces in Physics

• Speed: Distance traveled in a period of time (magnitude of velocity)

• Velocity: Speed moved in a direction• Acceleration: rate of increase of velocity• Momentum: mass of an object times the

velocity. A large object has more momentum than a small one moving at the same velocity

Collisions

• Collisions are a transfer of momentum

• When vehicles in motion collide, a change in momentum of one vehicle is met by a change in momentum of the other vehicle.

Newton’s Three Laws

• 1. Objects in motion stay in motion unless an external force is applied (law of inertia)

• 2. Force is equal to mass times acceleration (F=ma)

• 3. Every action has an equal and opposite reaction.

Gravity

• Physical bodies attract each other

• Gravity on Earth is why things fall and have weight

• Falling objects all accelerate at the same rate

• Acceleration due to gravity is about 9.8 m/s2

Photo: Richmond Times-Dispatch

Work

• When a force does work, it acts on a body and moves (or displaces) it

• Work is measured in joules

• Work equals force times displacement (W=fd)

image: Fastfission

Structure of matter

• Atom is the smallest unit of matter

• Atoms consist of a nucleus with protons and neutrons surrounded by a field of electrons

• Atoms group together to form molecules

States of Matter

• Solid, liquid, gas and plasma

• States change when temperature changes

• As states of matter change molecules get further apart and move around more easily

Density

• The amount of mass a substance has per its volume (D=m/V)

• In liquid or gas form, less dense substances float on more dense substances

Chemical Equations

• Show a chemical reaction using chemical abbreviations

• 2HCl + 2Na -> 2NaCl + H2

• 2 atoms hydrochloric acid (HCl) react with 2 atoms sodium (Na) to create 2 atoms salt (NaCl) and Hydrogen (H2)

• Nothing is wasted- everything on one side is on the other

• Sometimes energy is given off

Solubility

• Ability for a substance (the solute) to dissolve into another substance (the solvent)

• Once dissolved, a solution is formed• Increasing heat of the solvent allows more of

the solute to dissolve- like dissolving sugar in tea