paper 1 Flashcards
compound
A compound is a substance made up of two or more different types of atoms chemically bonded together in fixed proportions.
e.g. water (H₂O), carbon dioxide (CO₂), and sodium chloride (NaCl).
element
An element is a substance that consists of only one type of atom
e.g. oxygen (O), carbon (C), and hydrogen (H).
mixture
a substance with different elements or compounds not chemically combined together.
e.g. air (a mixture of gases), sand and salt, and salad (a mix of vegetables and dressing).
name 4 physical separation techniques
can only be used to separate mixtures.
filtration
distillation
crystallisation
chromatography
molecule
has any elements chemically combined even if they are the same element
e.g. CH₄
filtration
a physical separation technique
used to separate an insoluble solid from a liquid
we need…
- filter paper
- filter funnel
- conical flask
insoluble
the solid wont dissolve in the water
crystallisation
a physical separation technique
is used to separate a soluble solid from a liquid
e.g. salt and water
aq meaning
aq stands for aqueous, meaning a substance is dissolved in water.
why is it better to let the water evaporate in it’s own during crystallization?
certain chemicals will break down if we heat them
simple distillation
a physical separation technique
used when we want to separate a dissolved solid from a liquid but we want to keep the liquid
simple distillation method
- Heat the solution in a flask.
- The liquid with the lower boiling point evaporates.
- Vapour rises into a condenser, where it cools and turns back into liquid.
- The liquid is collected in a separate container, leaving the solute *behind.
fractional distillation
when we want to separate a mixture of different liquids
will only work if the liquids have different boiling points
fractional distillation method
- Heat the mixture in a flask.
- The liquid with the lowest boiling point evaporates first.
- Vapour passes through a fractionating column, which helps separate the components.
- The vapour cools in a condenser and turns back into liquid.
- Collect the liquids one by one as they condense at their specific boiling points.
paper chromatography
a physical separation technique
a process which allows us to separate substances based on their different solubilities.
process of paper chromatography
Preparation:
Draw a pencil line near the bottom of a sheet of chromatography paper and place small spots of the mixture on the line.
Stationary Phase:
Place the paper in a container with a small amount of solvent, ensuring the solvent is below the pencil line.
Movement:
The solvent (mobile phase) travels up the paper, carrying the mixture.
Separation:
Different substances move at different speeds and separate as they travel.
Result:
The separated substances appear as spots at various heights on the paper, forming a chromatogram.
why do we use pencil when drawing the starting line for paper chromatography?
because if we drew it with pen the pen ink could dissolve in the solvent and move up the paper
alpha scattering experiment method
took a piece of gold foil because we can hammer gold into very thin foil - just a few atoms thick
scientists then fired tiny alpha particles (positively charged) at the gold foil
found out that most of the particles passed straight through the gold foil without change in direction.
results
However sometimes an alpha particle was deflected (change in direction) as it passed through the gold foil.
Some even bounced straight back from the gold foil
what did the alpha scattering experiment method tell us
- the fact that most of the AP went straight through the GF meant that atoms are mainly empty space
- since some were deflected this meant that the centre of the atom must have a positive charge (++=REPELLED)
- Finally since some bounced back this told us that the centre of an atom must contain a great deal of mass
what did the alpha scattering experiment lead to?
it led to the plum pudding model being replaced by the nuclear model of atomic structure
who discovered the plum pudding model?
J.J. Thomson in 1904
he also discovered electrons in 1897
who discovered the nuclear model
Ernest Rutherford in 1911 after his alpha scattering experiment
he also discovered protons and the nucleus
who discovered the nucleus
Ernest Rutherford
who discovered neutrons
James Chadwick
what did James Chadwick discover?
discovered the neutron in 1932.
and that the nucleus also contains neutral particles
what is the charge of an atom and why
atoms have no overall charge since they have the same number of protons and electrons
so they cancel each other out
what are isotopes
Isotopes are atoms of the same element with different numbers of neutrons.
e.g. carbon
what are ions?
ions are atoms which have an overall charge.
that is because ions have lost or gained electrons.
- gained = negative
- lost = positive
e.g. Sodium ion (Na⁺) and Oxygen ion (O²⁻)
what is the relative atomic mass
The relative atomic mass is the average mass of an element’s atoms, weighted according to the relative abundances of its naturally occurring isotopes. It reflects the average mass of all isotopes
what do we call the elements that aren’t in a group?
we call them transition elements
why do all the elements in the same group have similar chemical properties
(react in the same way)
because they all have the same number of electrons in their outer energy level
describe the arrangement, movement and energy of particles in solids
Arrangement: Particles are closely packed in a regular, fixed pattern.
Movement: Particles vibrate in place but do not move freely.
Energy: They have low energy, only enough to vibrate in their fixed positions.
describe the arrangement, movement and energy of particles in liquids
Arrangement: Particles are still close together but are not in a fixed pattern, allowing them to move around each other.
Movement: Particles can slide past one another, allowing the liquid to flow.
Energy: They have more energy than solids, enough to move more freely within the liquid.
describe the arrangement, movement and energy of particles in gases.
Arrangement: Particles are far apart and move randomly and independently.
Movement: Particles move quickly in all directions.
Energy: They have high energy, allowing them to move freely and fill any container they are in.
name the interconversions between solids, liquids and gases. (6)
- Melting: Solid → Liquid
- Freezing: Liquid → Solid
- Evaporation: Liquid → Gas
- Condensation: Gas → Liquid
- Sublimation: Solid → Gas
- Deposition: Gas → Solid
what’s a boiling point
A boiling point is the temperature at which a substance changes from a liquid to a gas.
At this point, the substance has enough thermal energy for the particles to break free from the liquid phase and form a gas.
what’s a melting point
A melting point is the temperature at which a solid turns into a liquid.
At this temperature, the solid absorbs enough heat energy to break the bonds holding its particles in a fixed position, causing it to melt.
what’s an atom
is the smallest unit of an element that retains the chemical properties of that element
consists of a nucleus made up of protons and neutrons, and surrounded by electrons.
describe how the periodic table is arranged in
increasing atomic number
explain why the noble gases do not readily react using their electronic configurations.
they have full outer electron shells, making them stable and unreactive.
they don’t need to loose or gain an electron to be complete
write a word equation to represent the chemical reaction for salt
Sodium + Chlorine → Sodium Chloride (NaCl - table salt)
write a chemical equation to represent the chemical reaction for salt
2 Na (s) + Cl₂ (g) → 2 NaCl (s)
explain why carbon monoxide is poisonous.
it binds to haemoglobin in the blood more strongly than oxygen, reducing the blood’s ability to transport oxygen to cells and tissues.
describe how sulfur dioxide is formed in combustion reactions.
Sulfur dioxide (SO₂) is formed during combustion when fuels containing sulfur impurities burn. The sulfur reacts with oxygen in the air to produce SO₂:
S + O₂ → SO₂.
what’s the difference between short and long chains of hydrocarbons
long chains are less flammable and the boiling point increases
opposite for short ones
exothermic reactions
An exothermic reaction releases energy, usually in the form of heat, to the surroundings.
Examples include combustion and respiration.
Endothermic reactions
takes in energy from the surroundings.
so temperature of the surroundings decreases (colder)
what makes things acidic
Substances are acidic if they release hydrogen ions (H⁺) when dissolved in water. The higher the concentration of H⁺ ions, the stronger the acid.
