motion and chemical reactions

covalent compounds

covalent compounds

non-metals react to share electrons, forming a ______ bond

covalent compounds examples

• dihydrogen monoxide (H₂O)

• sulphur tetrachloride (SC₄)

• methane (CH₄)

ionic compounds

metals react with non-metals, transferring electrons, forming ions that attract because of opposite charges

ionic compounds examples

• calcium chloride (CaCl₂)

• magnesium nitrate (Mg(NO₃)₂)

• zinc (II) chloride (ZnCl₂)

• hydrochloric acid (HCl)

• sulfuric acid (H₂SO₄)

• nitiric acid (HNO₃)

• acetic acid (CH₃COOH)

common acids

• sodium hydroxide (NaOH)

• potassium hydroxide (KOH)

• ammonia (NH₃)

• barium hydroxide (Ba(OH)₂)

common bases

methyl orange

colours on indicator:

red - acid, yellow/orange - base

bromothymol blue

colours on indicator

yellow - acid, green - neutral, blue - base

red litmus paper

colours on indicator:

red - neutral, acid

blue - base

blue litmus paper

colours on indicator:

red - acid

blue - neutral, base

meth, eth, prop, but, pent, hex, hept, oct, non, dec

prefixes from 1-10

C_nH_2n+2

alkanes formula

C_nH_2n

alkenes formula

C_nH_2n-2

alkynes formula

polymers

large molecules made of smaller repeating units called monomers

naturally occuring polymers examples

• proteins (polypeptin)

• rubber

• starch

• cellulose (in plants)

• DNA

synthetic polymers examples

plastics and artificial fibres such as:

• PVC

• nylon

• PET

• polyethene

• polystyrene

law of conservation of mass

mass cannot be created nor destroyed

chemical reactions

atoms are rearranged, mass of reactants = mass of products

3 types of combustion

• metal combustion

• hydrocarbon fuel combustion

• hydrogen fuel combustion

metal + oxygen —> metal oxide

metal combustion general equation

metal combustion example(s)

• 2Mg + O₂ —> 2MgO

hydrocarbon + oxygen —> carbon dioxide + water

hydrocarbon fuel combustion general equation

hydrocarbon fuel combustion example(s)

• CH₄ + 2O₂ —> CO₂ + 2H₂O

• C₂H₄+ 3O₂ —> 2CO₂ + 2H₂O

• 2C₄H₆ + 11O₂ —> 8CO₂ + 6H₂O

2H₂ + O₂ —> 2H₂O

hydrogen fuel combustion

acid + base —> salt + water

neutralisation general equation

• metal + acid —> salt + hydrogen gas

• metal + carbonate —> salt + carbon dioxide + water

metal reactions general equations

Mg + 2HCl —> MgCl₂ + H₂

magnesium + hydrochloric acid —> magnesium chloride + hydrogen gas

H₂SO₄ + 2NaOH —> Na₂SO₄ + 2H₂O

sulfuric acid (hydrogen sulfate) + sodium hydroxide —> sodium sulfate + water

corrosion

involves similar reactants as metal combustion, but is a slower reaction

corrosion example

rusting of iron;

4Fe + 3O₂ —> 2Fe₂O₃

precipitation reaction

two soluble solutions forming a soluble solution and an insolube solid (precipitate)

precipitation example

Ba(NO₃)_2(aq) + Na₂CO_3(aq) —> 2NaNO_3(aq) + BaCO_3(s)

neutralisation example

2HNO₃ + K₂O —> 2KNO₃ + H₂O

2NaCl —> 2Na + Cl₂

decomposition example

3 types of decomposition reactions

• electrolysis

• photolysis

• thermal decomposition

activation energy

the minimum amount of eergy needed to kickstart a chemical reaction

exothermic reactions

reactions in which reactants have more energy than the products (energy is released into the surroundings)

endothermic reactions

reactions in which the reactans have less energy than the products (energy is absorbed from the surroundings)

exothermic reactions examples

• respiration

• combustion

• corrosion

endothermic reactions examples

• photosynthesis

• decomposition

5 factors that change the rate of reactions

• temperature

• concentration

• catalysts

• agitation

• surface area

how increasing temperature affects the rate of reaction

causes the molecules to move faster which increases the chance of collisions between reactants and therefore increasing the rate of reaction

eliminates in “clumps” of reactants and allows them to move freely and react

how agitation affects the rate of reaction

increases the likehood of collisions by decreasing the space between atoms

how increased concentration affects the rate of reaction

how increased surface area affects the rate of reaction

increased the exposure one reactant to another hence increasing the likelihood of collisions

how a catalyst affect the rate of reaction

speed up the rate of reaction typically by lower the activation energy or changing the reaction mechanism

collision theory

“for chemicals to react, they need to collide and have enough energy”

—> the more collisions, the higher the rate of reaction

NH₄⁺

ammonium ion

OH^-

hydroxide ion

NO₃^-

nitrate ion

HCO₃^-

hydrogen carbonate ion

SO₄^2-

sulphate ion

CO₃^2-

carbonate ion

PO₄^3-

phosphate ion

distance

length of the line/path between two points (scalar quantity)

displacement

length of the straight line between two points (vector quantity)

speed

change in distance over time

average speed

change in total distance over total time taken

instantaneous speed

the speed of an object during a very small duration of time

scalar vs. vector

only magnitude vs. magnitude and direction

acceleration

change in speed/velocity over time (can be vector or scalar)

how can an object accelerate (change velocity) whilst the speed remains the same?

• Acceleration is a change in velocity, either in its magnitude or in its direction, or both.

• In uniform circular motion, the direction of the velocity changes constantly, so there is always an associated acceleration, even though the speed might be constant.

SI units

(displacement/distance) metres

(time) seconds

(speed/velocity) ms^-1

(acceleration) ms^-2

(mass) kg

converting between km/h and m/s

km/h —> m/s : divide by 3.6

m/s —> km/h ; multiply by 3.6

ways of measuring speed

• speedometer: uses electrical currents

• radar guns: uses radio wave frequency

• mobile speed cameras: sensors

gradients of graphs

• distance - time graph —> speed

• displacement - time graph —> velocity

• velocity - time graph —> acceleration

areas below graphs

• velocity - time —> displacement

• speed - time —> distance

• acceleration - time —> velocity

reaction time

the time it takes for someone to react to an emergency (in a car)

0.15 - 0.30 s

typical reaction time for an alert and concentrating person

reaction distance

the distance covered by the car during the reaction time

braking distance

the distance covered by the car after the brakes have been applied

stopping distance

reaction distance + braking distance

factors that slow down reaction time

• passengers

• speaking or texting on the phone, changing music or working navigation systems

• influence of drugs or alcohol

• age

• fatigue

how do mobile speed cameras work

• electronic sensors on the road, accurately measure the speed

• if the speed exceeds the legal limit, a photograph is taken

factors the led to road accidents

essentially factors that increase reaction time and create districation from the road

forces acting on an object when its falling down

• gravitational force

• air resistance/drag

the velocity of a falling object

as the object falls, it will initially accelerate due to gravity. Its acceleration will soon approach 0 due to air resistance.

formula for acceleration

a = (v-u)/t

v = at +u

final velocity formula (with acceleration, time and initial velocity)

v² = u² + 2as

final velocity formula (with initial velocity, acceleration, displacement)

s = ut + ½at²

displacement formula (with initial velocity, time, acceleration)

net force

the vector sum of all forces that act upon an object

newton’s first law

• an object will remain stationary unless acted upon by an unbalanced force

• an object in motion will remain at the same speed and direction unless acted upon by an unbalanced force

inertia

an object’s tendency to resist motion

example(s) of the first law

people in vehicles moving forward when the vehicle comes to a stop

safety features of cars to minimise the effect of inertia

• seat belts: inertia reels lock the belts when they are pulled abruptly

• airbags: prevent collion with hard surfaces and minimise space to move

• head restraints: prevent abrupt backward motion of the head and hence whiplash injuries

newtons’s second law of motion

An onject will accelerate in the direction of an unbalanced force acting upon it.

The size of this acceleration depends upon the mass of the object and the size of the force acting.

examples of the second law

• pushing empty cart vs. a cart full of bricks

• pushing little kids vs. big kids on skateboards

F = ma

formula relating force, mass and acceleration

newton’s third law of motion

for every action force, there is an equal and opposite reaction force

• a nail getting hit by a hammer, the mail exerts an equal force back on the hammer

• a sprinter pushes back on the starting blocks, the strating blocks push forward on the sprinter

• a book resting on a table exerts its weight force onto the table, the table exerts an equal support force

• an octopus squirts water out as jets through a tube just below its head. The water jets push back on the octopus, propellng it in the opposite direction

• standing on the skateboard and pushing against a wall, the wall pushes back, making the person move away

examples of third law

first law applications in space

• space has no air and therefore no air resistance to slow down a spacecraft.

• inertia ensures that any rocket launched continues to travel in its initial speed and direction forever (e.g. Voyager I in 1977)

second law applications in space

• At launch, a rocket is at its heaviest and needs to break free of Earth’s gravity

• As the rocket rises (due to a large force acting on it) it experiences less air resistance than at sea level, due to the atmospshere becoming thinner

• fuel tanks are emptied and jettisoned, making the rocket lighter

• overall a smaller force is needed to kepp it accelerating

third law applications in space

• rockets ignite and expek exhaust gases from them

• the action force: expulsion of exhaust gases

• the reaction force pushes the rocket in the opposite direction (upwards)

forms of energy

• kinetic energy

• sound energy

• light energy

• heat energy

• electrical energy

• potential energy

types of potential energy

• chemical potential

• gravitational potential

• elastic potential

kinetic energy

energy of moving objects

½mv²

kinetic energy formula

relationship between stopping distance and speed

the higher the speed, the mroe the stopping distance

if the speed is doubled, the distance would increase by around a factor of four