3.1 Flashcards
describe the combustion of elements in oxygen, including magnesium
•bright white flame
•white powder produced (magnesium oxide)
magnesium + oxygen —> magnesium oxide
2Mg (s) + O₂ (g) —> 2MgO
describe the combustion of elements in oxygen, including hydrogen
•put lit splint into gas, if squeaky pop sound, hydrogen is present (test for hydrogen)
•explosive reaction
hydrogen + oxygen —> water
2H₂ (g) + O₂ (g) —> 2H₂O (l)
describe the combustion of elements in oxygen, including sulfur
•bright blue flame
sulfur + oxygen —> sulphur dioxide
S (s) + O₂ (g) —> SO₂ (g)
do non-metal oxides turn acidic or alkaline when reacting with oxygen and then dissolved in water (if soluble)
acidic in solution
e.g. sulfur + oxygen —> sulfur dioxide - pH1
do metal oxides turn acidic or alkaline when reacting with oxygen and then dissolved in water (if soluble)
alkaline in solution
e.g. magnesium + oxygen —> magnesium oxide (doesn’t dissolve) - around pH10
what are signs of a chemical reaction
new product formed
usually irreversible
change in appearance
temperate change
light given off
what are signs of a physical reaction
no new product formed
usually reversible
changes of state
describe the pH scale
pH1-6 is an acid, 1 being very acidic
pH7 is neutral
pH8-14 is an alkalis, 14 being very alkali
what does an atom consist of
atoms consist of a nucleus containing protons and neutrons, surrounded by electrons in shells - every atom has no overall charge (neutral) as there are the same number of protons (+1) as electrons (-1)
what do you call the transition of a substance directly from a solid state to a gas state
sublimation
what do you call the transition of a substance directly from a gas state to a solid state
deposition
bromine slowly fills the container until it is all the same colour, why does this happen
diffusion - spreading out of particles from an area of high concentration to low concentration
(same with air freshener, potassium manganate (KMnO₄) in water - dissolve and diffusion and dilution of potassium manganate)
explain why hot water evaporates more quickly than cold water
hot water already has a lot of energy, so therefore it evaporates quicker (breaks the bonds between the two molecules) as the particles don’t have to gain lots of energy to turn into gas.
which method can be used to separate an insoluble solid from a liquid
filtration
which method can be used to separate a mixture of liquids with different boiling points
distillation
what are four ways that we can change the rate of diffusion
•change the temperature - particles are moving quicker or slower
•stirring a solution – particles physically being moved quicker
•change surface area – easier to dissolve
•change the volume – end result faster but not particles faster
describe the diffusion tube
a tube, with two bungs at each end, contains two pieces of cotton wool; one with concentrated hydrochloric acid and the other with concentrated ammonia, they are placed separately at either end of the tube
ammonia diffuses faster because it has a smaller mass (mass of 17) than the hydrochloric acid (mass of 36.5), you can see this because they both meet and react to form ammonium chloride (white solid) closer to the end where the cotton wool with hydrochloric acid is
equation of reaction:
ammonia (NH₃ (g)) + hydrochloric acid (HCl (g)) —> ammonium chloride (NH₄Cl (s))
how can you tell if you have a pure piece of magnesium
measure it’s melting point -
pure - melts at a specific temperature
impure - melts over a range of temperatures
how can you tell if you have pure water
measure it’s boiling point -
100°C for pure water
impure water boils over a range of temperatures
do metals (or hydrogen) always lose or gain electrons
metals (or hydrogen) always lose electrons to form positive ions
do non-metals always lose or gain electrons
non-metals always gain electrons to form negative ions
what is the formula for the reaction between aluminium and iron (lll) oxide
2Al + Fe₂O₃ —> 2Fe + Al₂O₃
