y9 Science revision Flashcards
define an element
contains only one type of atom
define a compound
two or more different atoms chemically joined/ bonded together
define a mixture
two or more different elements or compounds NOT chemically joined/ bonded together.
define an atom
smallest particle of an element that is involved in a chemical reaction
define a molecule
two or more atoms chemically joined/ bonded together
what is shown on the left side of a chemical reaction?
reactants
what is shown on the right side of a chemical reaction
products
write a word equation for the formation of water from the reaction between hydrogen and oxygen
hydrogen + oxygen —> water
write a symbol equation for the formation of water from the reaction between hydrogen and oxygen
H2 + O2 —> H2O
define a solute
a substance that dissolves in a solvent
define a solvent
liquid that can dissolve a solute
define a solution
a mixture of a solute and solvent
how can an insoluble solid be separated from a liquid?
filtration
how can a soluble solid be separated from a solution
evaporation then crystallisation
how can immiscible (don’t mix) liquids be separated?
Use a pipette to extract one layer of liquid
how can miscible (do mix) liquids be separated?
distillation
what physical property is used in distillation?
boiling points - separates at different temperatures
what are the 3 steps in distillation?
evaporate, condense and collect
what is chromatography?
separates colours in mixture
what are the 5 models of the atom?
Tiny spheres, Plum pudding,Nuclear, Bohr’s and today’s model
who was responsible for each model of the atom?
J Dalton - Tiny spheres, JJ Thomson - Plum pudding, E Rutherford - Nucleus, Niels Bohr - Bohr’s, J Chadwick - Today’s model
describe the plum pudding model
solid ball of positive charge with electrons embedded throughout it
describe the nuclear model
positive nucleus at the centre, with electrons at the edge of the atom - rest is empty space
what evidence gave the nuclear atom as mainly empty space?
Positive Helium nucleus (alpha particle) fired at a gold foil - many went straight through
what evidence gave the nuclear atom as having a positive nucleus?
Positive Helium nucleus (alpha particle) fired at gold foil - some slightly deflected as they went past the edge of the nucleus. Those fully deflected were repelled by the nucleus
what did Bohr’s model change about the nuclear model?
Electrons were no longer at the edge of the atom but in energy shells
how did today’s atomic model change from Bohr’s?
Discovery of neutrons, now added these to the nucleus
what is the order of the discovery of the sub atomic particles?
Electron, proton then neutron last
what is the mass of each sub atomic particle?
Proton = 1, Electron = almost one, Neutron = 1
what is the charge on each subatomic particle?
Protons = +1 Electrons = -1 Neutrons = 0
where is most of the mass of an atom found?
in the nucleus
what subatomic particles are found in the nucleus?
protons and neutrons
where are electrons found?
in energy shells orbiting the nucleus
why does the atom have no overall charge?
number of protons = number of electrons
what does the relative atomic mass represent?
protons and neutrons
what does the atomic number represent?
Number of protons = number of electrons
how do you calculate the number of neutrons in an element?
Mass number - Atomic number
what are the numbers of electrons allowed in the electron shells?
1st she’ll = 2 electrons, 8 electrons are allowed in every shell after that
what is the electron configuration showing?
the number of electrons in each shell (e.g. 2,6)
Define an isotope?
Atoms are the same elements with a different number of neutrons
Approximately how large are atoms?
Radius is about 0.1nm
how large is the nucleus compared to the whole atom?
about 1/10000 the size
What is abundance?
The % of atoms in a sample with a particular mass
in the modern periodic table, how are the atoms arranged?
By their atomic number and in groups according to chemical properties
why do elements in the same group have similar properties?
because they all have the same number of electrons in their outer shell
before the discovery of protons, neutrons and electrons, how did scientists organise the elements?
by their atomic weight
why did Mendeleev leave gaps in his periodic table?
for elements that had not yet been discovered
which discovery meant that organising elements by their atomic weight not always correct?
Isotopes
where are metals on the periodic table found?
to the left and bottom of the periodic table
what are the names of groups 1, 7 & 0?
1 = Alkali metals, 7 = Halogens, 0 = Noble gases
why are noble gases inert (unreactive)?
they have a full outer shell of electrons so don’t need to lose or gain electrons to be stable
what does the group number tell you?
number of electrons in outer shell
what does the period number tell you?
number of electron shells
give some properties of group 1 metals
silver coloured, shiny, soft and very reactive
why are group 1 metals more reactive as you go down the group?
larger atoms so outer electron is further away from the attractive positive nucleus, so electron is more easily lost
what do group 1 metals produced when added to water?
Metal Hydroxide + Hydrogen
are halogens metals or non - metals?
non - metals
why are group 7 halogens more reactive as you go up the group?
smaller atoms so outer electron is closer to the attractive positive nucleus, so easier to attract an electron
what is the central block in the periodic table called?
transition metals
compare the hardness of group 1 & transition metals
Transition metals are much harder than group 1 metals
state which cell is smaller: a prokaryote cell or eukaryote cell
prokaryotic
give one example of a prokaryotic cell and two examples of eukaryotic cells
Prokaryotic = bacteria Eukaryotic = animal and plant cells
state 2 small similarities between a prokaryotic and eukaryotic cell
Both have a cytoplasm
Both have a cell membrane
state one difference between prokaryotic and eukaryotic cell
eukaryotic cells have genetic material enclosed in a nucleus
Prokaryotic cells do not have genetic material enclosed in a nucleus. It is a single DNA loop
Parts of a bacterial cell
cell membrane cell wall circular strand of DNA Plasmid Cytoplasm
state how you convert from centimetres (cm) to millimetres (mm)
times by 10
state how you covert from millimetres (mm) to micrometers ( um)
times by 1000
what is the function of a nucleus
contains genetic information in the form of chromosomes and controls the activities of the cell
what is the function of the cytoplasm?
where many chemical reactions occur in a cell. It contains many enzymes for these reactions
what is the function of a cell membrane?
partially permeable; controls the movement of substances into and out of the cell
what is function of a mitochondria?
this is the site of aerobic respiration and release of energy
what is the function of a ribosome?
this is the site of protein synthesis
what is the function of a chloroplast?
Contains a green pigment called chlorophyll which absorbs light for photosynthesis
what is the function of a vacuole?
stores sap ( a weak solution of salts and sugars)
what is the function of a cellulose cell wall?
Rigid; supports and strengthens the cell
what is the function of a plasmid?
a small ring of additional DNA found in bacteria
state three organelles that present in a plant cell that are not present in an animal cell?
chloroplast
vacuole
cellulose cell wall
state one organelle that is present in both bacteria and plant cells
cell wall (however only the plant cell wall is made of cellulose) Or cell membrane Or cytoplasm
state two. differences between a bacterial cell (prokaryote) and a plant cell (eukaryote)
plant cells contain genetic information in a nucleus and bacteria do not
plant cells contain mitochondria and bacteria do not
recall the equation for calculating magnification
magnification = size of image/ size of object (actual size)
describe and explain the function of sperm cells as a specialised cell
contain many mitochondria in their mid - piece for energy to move. Have a flagellum (tail) to swim towards the egg cell
describe and explain the function of muscle cells as a specialised cell
contain many mitochondria which supplies energy for muscle contraction
describe and explain the function of root hair cells as a specialised cell
contain many mitochondria to supply energy for active transport of ions
describe and explain the function of leaf palisade cells as a specialised cell
contain many chloroplasts which contains chlorophyll to absorb light for photosynthesis
describe and explain the function of xylem as a specialised cell
dead, hollow cells with no cytoplasm that join to end to end to form xylem tubes for the transport of water freely up the plant. The cell walls are strengthened with lignin
describe and explain the function of phloem as a specialised cell
cells joined end to end to form phloem tubes. Phloem cells have very few organelles e.g. no mitochondria to allow more room for the transport of cell sap
