Science - the knowledge obtained by observing natural events and conditions in order to discover facts and formulate laws or principles that can be verified or tested
Physical science - the scientific study of nonliving matter
A. Chemistry - the study of how matter interacts with other matterB. Physics - the study of energy and how energy affects matter
Scientific methods - a series of steps followed to solve problems
Observation - the process of obtaining information by using the senses
Hypothesis - a possible explanation or answer to a question: it must be testable
Controlled experiment - compares the results from a control group with the results from an experimental group
Data - any pieces of information acquired through experimentation
Matter - anything that has mass and takes up space
Volume - the amount of space taken up by an object
A. Liquid volume - most often expressed as Liters (L) or Milliliters (M)
1. Meniscus - the curve at a liquid’s surface by which one measures the volume of a liquid
B. Volume of a regularly shaped solid object Volume = length X width X height
C. Volume of an irregularly shaped solid object (page 40 paragraph 2)
1.You measure the amount of water the object displaces (take the before measurement and subtract it from the after measurement. The measurement will be in ml, convert it to cm³ (1 ml = 1cm³)
Mass - a measure of the amount of matter in an object: Constant no matter where the object is located.
A. The SI unit for Mass is the kilogram (kg)
Weight - a measure of the gravitational force exerted on an object: An object’s weight can change depending on where in the universe it is.
A. The SI unit for weight is the Newton (N)
Inertia - the tendency of an object to resist being moved or, if the object is moving, to resist a change in speed or direction.
A. The more massive an object is, the greater the inertia
Physical property - a characteristic of a substance that does not involve a chemical change, such as density, color, hardness, malleability, ductility, solubility, thermal conductivity and state of matter.
A. Density - is the amount of matter in a given space or volume
B. Thermal conductivity - the rate at which a substance transfers heat
C. Malleability - the ability of a substance to be rolled or pounded into thin sheets
D. Ductility - the ability of a substance to be pulled into a wire
E. Solubility - the ability of a substance to dissolve in another substance
Formula for Density density = mass volume
1.In a liquid, the denser layers will sink to the bottom
2.If the density of an object is less than the density of water it will float (water has a density of 1.0 g/cm³)
3. Each substance has its own density, so density can be used to identify substances
Physical Change - a change of matter from one form to another without a change in chemical properties
A. Freezing, melting, cutting, bending, and dissolving.
Chemical properties - a property of matter that describes a substance’s ability to participate in chemical reactions. They can only be observed when a chemical change might happen.
A. Flammability - is the ability of a substance to burn
B. Reactivity - the ability of two or more substances to combine and form one or more new substances
Characteristic properties - the properties that are most useful in identifying a substance: They can by physical or chemical.
Chemical change - happens when one or more substances are changed into new substances that have new and different properties.
A. Seven Signs of a chemical change
1. change in odor2. change in color3. production of heat4. Fizzing
5. Foaming6. sound being given off7. light being given off
B. Chemical changes are not easily reversed.
Composition - is the type of matter that makes up the object and the way that the matter is arranged
A. Physical changes do not change the composition of an object.
B. Chemical changes do change the composition of an object
3 States of Matter - the physical forms of matter, which include solid, liquid, and gas
A. Atoms and Molecules are always in motion
Solid - the state of matter in which the volume and shape of a substance are fixed
A. Definite shape, definite volume
B. Particles are very close together (stronger attraction than in a liquid or gas)
C. Particles vibrate but are locked in place by the particles around it.
Liquids - the state of matter that has a definite volume but takes the shape of its container
A. Definite volume but no definite shapeB. Particles slide past each other
Surface tension - the force that acts on the surface of a liquid and that tends to minimize the area of the surface
A. This is what causes water droplets to form
Viscosity - a liquid’s resistance to flow
A. Liquids with a high viscosity flow slowly (examples - molasses, honey)
B. Liquids with a low viscosity flow quickly (examples - water, vinegar)
Gas - the state of matter that does not have a definite volume or definite shape
A. No definite shape or definite volumeB. Particles move quickly, much weaker attraction than in solid or liquid
(Gas particles have a large amount of space between them)
Behavior of Gases (Temperature, pressure and volume of a gas are linked. Changing one of these factors changes the other two)
A. Temperature - a measure of how fast the particles in an object are moving.
B. Volume - the amount of space that an object takes up.
C. Pressure - the amount of force exerted per unit of area of a surface
Boyle’s Law - the volume of a gas is inversely proportional to the pressure of a gas when temperature is constant. (pressure increases/volume decreases or pressure decreases/volume increases)
Charles’s Law - the volume of a gas is directly proportional to the temperature of a gas when pressure is constant. (temperature increases/volume increases or temperature decreases/volume decreases)
Change of state - change of a substance from one physical state to another
A. All changes of state are physical changes
B. Particles of a substance move differently depending on the state of the substance
C. Particles have different amounts of energy in different states
Endothermic change - energy is gained by the substance as is changes state
Exothermic change - energy is removed from the substance as it changes state
Melting - change of state in which a solid becomes a liquid by adding energy
Melting point - the temperature at which a substance will melt.
Freezing - the change of state from a liquid to a solid by removing energy
Freezing point - the temperature at which a liquid changes into a solid
* Freezing and Melting occur at the same temperature
Evaporation - the change of state from a liquid to a gas by adding energy: It occurs at the surface of a liquid.
Boiling - the conversion of a liquid to a vapor when the vapor pressure of the liquid equals the atmospheric pressure.
A. Boiling point - the temperature at which a liquid boils
B. The change of a liquid to a vapor takes place throughout the liquid
C. Water boils at 100˚C at sea level (the higher the altitude, the lower the boiling point)
Condensation - the change of state from a gas to a liquid
A. Condensation point - the temperature at which the gas becomes a liquid
Pure substance – a substance in which there is only one type of particle (Can be either a single element or a single compound)
Element – a pure substance that cannot be separated or broken down into simpler substances
1. Metal – an element that is shiny and that conducts heat and electricity well (Strong and malleable)
2. Nonmetal – an element that conducts heat and electricity poorly (Brittle and is not malleable)
3. Metalloid – an element that has properties of both metals and nonmetals (Called semi-conductors)
Compound – a substance made up of atoms of two or more different elements joined by chemical bonds
A. Cannot be separated by physical means
Mixture – a combination of two or more substances that are not chemically combined
A. Can be separated by physical means
Dissolving – the process in which particles of substances separate and spread evenly throughout the mixture
Solution – a single substance composed of particles of two or more substances that are distributed evenly among each other
A. Solute – the substance that is dissolvedB. Solvent – the substance in which the solute is dissolved
Concentration – the amount of a particular substance in a given quantity of a mixture, solution, or ore
Solubility – the ability of one substance to dissolve in another at a given temperature and pressure
Suspension – a mixture in which particles of a material are dispersed throughout a liquid or gas but are large enough that they settle out
Colloid – a mixture consisting of tiny particles that are intermediate in size between those in solutions and those in suspensions
Motion - an object’s change in position relative to a reference point
Reference point - when you watch an object in relation to another object, the object that appears to stay in place is the reference point.
A. Nonmoving - the Earth’s surface, trees, buildings
B. Moving - a hot air balloon, a cloud
Speed - the distance traveled divided by the time interval during which the motion occurred.
A. SI unit for speed- meters per second (m/s)
B. Average speed = total distance total time
Velocity - the speed of an object in a given direction
A. Velocity is different than speed, it must include a reference direction
B. An object’s velocity is constant only if its speed and direction do not change. Therefore, constant velocity is always motion along a straight line
Acceleration - the rate at which velocity changes over time
A. An object accelerates if its speed, direction, or both change
B. An increase in velocity is often called positive acceleration
C. A decrease in velocity is often called a negative acceleration, or deceleration
final velocity - starting velocity
Average acceleration =------
Time it takes to change velocity
Centripetal acceleration - acceleration that occurs in a circular motion; its velocity is always changing, so it is accelerating
Force - a push or pull exerted on an object in order to change the motion of the object
A. Force has size and directionB. Just because a force acts on an object doesn’t mean motion will occur
Newton (N) - the SI unit for force
Net Force - the combination of all the forces acting on an object
A. When the forces on an object produce a net force of 0 N, the forces are balanced.
1. Balanced forces do not cause a change in motion
B. When the net force on an object is not 0 N, the forces on the object are unbalanced.
2. Unbalanced forces cause a change in motion
C. Net forces acting in the same direction are added together (example p. 125, figure 3)
25N+20N=45N
D. When forces are in opposite directions, subtract the smaller force from the larger force
(example p. 126, figure 4)
20N25N=5N (net force)
Friction - a force that opposes motion between two surfaces that are in contact
A. The amount of friction between two surfaces depends on two factors:
1. The amount of force pushing the two surfaces together
2. The roughness of the surfaces (rough surfaces have more microscopic hills and valleys than smooth surfaces)
There are two types of friction:
A. Kinetic friction - friction between moving surfaces
1. Sliding kinetic friction - surfaces sliding past each other
2. Rolling kinetic friction - using wheels requires a smaller force than sliding friction, used in transportation
B. Static friction - when a force is applied to an object but does not cause the object to move
1. Static friction disappears as soon as the object starts moving and then kinetic friction immediately occurs
Three ways to reduce friction:
A. Lubricants - substances that are applied to surfaces to reduce the friction between surfaces (Examples: motor oil, wax, grease)
B. Switch from sliding to rolling friction, using wheels and ball bearings
C. Make the surfaces rubbing against each other smoother
Two ways to increase friction:
A. Make surfaces rubbing against each other rougherB. Increase the force pushing the surfaces together
Gravity - the force of attraction between objects that is due to their mass
Law of Universal Gravitation - all objects in the universe attract each other through gravitational force.
Newton stated that the size of gravitational force depends on two things:
A. Gravitational force increases as mass increases (example: p.136, figure 3)
B. Gravitational force decreases as distance increases (example: p137, figure 5)
Objects fall to the ground at the same rate because the acceleration due to gravity is the same for all objects.
A. Acceleration depends on both force and mass
B. Heavier objects experience greater gravitational force but are harder to accelerate due to their greater mass (they have more inertia),
so these forces balance out
Acceleration - the rate at which velocity changes
Acceleration due to gravity = 9.8 m/s²
Formula for calculating the change in velocity (V) of a falling object:
A. v = g t v - velocityg - acceleration due to gravity (9.8m/s²)t - time
Air resistance - the force that opposes the motion of objects through air
A. The amount of air resistance depends on the size, shape and speed of the object
Terminal Velocity - the constant velocity of a falling object when the force of air resistance is equal in magnitude and opposite in direction to the force of gravity.
Free Fall - the motion of a body when only the force of gravity is acting on it.
A. Can only occur in space or a vacuum(A vacuum is a place in which there is no matter)
B. Astronauts float because of free fall
Orbiting - when an object is traveling around another object in space
A. An object in orbit is always in free fall
Centripetal Force - the unbalanced force that causes objects to move in a circular path
Projectile Motion - the curved path that an object follows when thrown, launched, or otherwise projected near the surface of Earth. It has 2 components.
A. Horizontal motion - motion parallel to the ground
1. Gravity does NOT affect the horizontal component of projectile motion
B. Vertical motion - motion perpendicular to the ground
2. Gravity pulls objects down at an acceleration of 9.8m/s²
Newton’s First Law of Motion - an object at rest remains at rest, and an object in motion remains in motion at constant speed and in a straight line unless acted on by an unbalance force.
Inertia - the tendency of an object to resist any change in motion
A. The larger the mass of an object, the larger the inertia
Newton’s Second Law - the acceleration of an object depends on the mass of the object and the amount of force applied
A. F = m aForce = mass × acceleration
Newton’s Third Law - whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first (This law can simply be stated as follows: all forces act in pairs)
Momentum - a quantity defined as the product of the mass and velocity of an object
A. The more momentum an object has, the harder it is to stop the object or change its direction
1. p = m v(P) momentum = mass velocity
The Law of Conservation of Momentum - any time objects collide, the total amount of momentum stays the same
Pressure - the amount of force exerted per unit area of a surface
A. P = f apressure = force area
Work – the transfer of energy to an object by using a force that causes the object to move in the direction of the force
A. For work to be done 2 things need to happen
1. The object moves as a force is applied
2. The direction of the object’s motion is the same as the direction of the force
B. W = F × dWork = Force × distance
1. The SI unit for work is the Joule which stands for the Newton-meter (n × m)
Power – the rate at which work is done or energy transferred
A. P = W ÷ t Power = Work ÷ time
1. The SI unit for power is the watt.
Machine – a device that helps do work by either overcoming a force or changing the direction of the applied force
A. Work input – the work done on a machine
B. Work output – the work done by a machine
Machines make work easier by changing the size or direction (or both) of the input force.
1. The same amount of work is done with or without a machine. What changes is how much input force you have to do.
2. When using the formula for work, if we are willing to spread the force out over a longer distance, the force needed goes down, making it easier for us.
Mechanical advantage – a number that tells you how many times a machine multiplies force.
A. Mechanical advantage (MA) = output force input force
Mechanical Efficiency – a quantity, usually expressed as a percentage, that measures the ratio of work output to work input
work output
Mechanical efficiency = ------× 100
work input
Ideal machine – a machine that has 100% mechanical efficiency (that would mean that all work input transfers through as work output)
A. Ideal machines are impossible to build because a machine has moving parts, and some work input is lost to friction
B. One way to increase efficiency is to use lubricants
1. Lever – a simple machine that has a bar that pivots at a fixed point, called a fulcrum
A. First-class levers – the fulcrum is between the input force and the load
1. Examples: a balance scale, a seesaw, oars on a row boat, scissors
B. Second-class levers – the load is between the fulcrum and the input force
2. Examples: wheelbarrow, bottle opener, a door
C. Third-class levers – the input force is between the fulcrum and the load
3. Examples: shovel, lacrosse stick, baseball bat, golf club, canoe paddle, hammer, human arm
2. Pulley – a simple machine that consists of a wheel over which a rope, chain or wire passes
A. Fixed pulley – the pulley is attached to something that does not move
B. Moveable pulley – the pulley is attached to the object that moves
C. Block and tackle – when a fixed and moveable pulley is used together
3. Wheel and axle – a simple machine consisting of two circular objects of different sizes: the wheel is larger than the axle
A. mechanical advantage of a wheel = radius of the wheel ÷ radius of the axle
4. Inclined plane – a simple machine that is a straight, slanted surface (also called a ramp)
A. You use less force by spreading the force over a longer distance
B. Mechanical advantage of inclined planes = distance of ramp ÷ height of ramp
5. Wedge – a simple machine that is made up of two inclined planes that move
A. Examples: knife, axe, front teeth, doorstops,
6. Screw – a simple machine that consists of an inclined plane wrapped around a cylinder
A. Examples: a screw, a twist on bottle cap, a spiral staircase
B. The closer the threads are together, the greater the mechanical advantage
5. Compound machine – a machine made of more than one simple machine