Download Year 8 Science Assessment Point 2

light energy
carbon
dioxide
water
glucose
oxygen
Y8 4.4 Bioenergetics
chlorophyll
Photosynthesis
6CO2
light energy
6H2O
chlorophyll
C6H12O6
Exercise:
• Uses a combination of aerobic and anaerobic
respiration in order to supply energy, quick
enough to cells.
• After we exercise we must get rid of lactic acid
by reacting it with oxygen = oxygen debt.
• This is why we are out of breath after exercise.
Anaerobic Respiration in yeast
glucose
Ethanol
Carbon
dioxide
energy
Anaerobic respiration takes place when
there is no oxygen available.
GOOD: Can produce some energy when
there is no oxygen
GOOD: Can produce energy very quickly
BAD: Produces very small amount of energy
BAD: produces lactic acid which is toxic
Anaerobic Respiration in animals
lactic
acid
glucose
glucose
oxygen
energy
carbon
dioxide
6O2
6CO2
Key words:
1. Photosynthesis: Using light energy to
split water and carbon dioxide to make
glucose and oxygen
2. Limiting factor: A factor that affects
the rate of reaction. When the factor is
increased the rate of reaction goes up
3. Aerobic respiration: Respiration using
oxygen to release energy in the form of
ATP to cells
4. Anaerobic respiration: Respiration with
no oxygen to release energy in the form
of ATP to cells
At the start temperature is a limiting factor,
once the enzymes have been destroyed no
photosynthesis can take place at all
water
Aerobic Respiration
C6H12O6
6O2
6H2O
Investigating Photosynthesis
• Count the number of oxygen bubbles in a set
amount of time.
• As oxygen is a product of photosynthesis,
the more oxygen produced = the quicker the
rate of photosynthesis
At the start
light
intensity is
the limiting
factor. Once
the graph
levels out
temperature
and carbon
dioxide
concentratio
n becomes
limiting
factors
Y8 5.3 Quantitative Chemistry
Conservation of mass: Mass is
never lost or gained, atoms are
just rearranged
H2
Please turn over
•
•
•
•
•
Compound
NH3
Products
Reactants
N2
Count the number of blue and
white atoms on the left and on the
right, are they the same?
Chromatography can be used to separate
mixtures of coloured compounds.
A spot of the mixture is placed near the
bottom of a piece of chromatography
paper and the paper is then placed in
water.
A pencil line is drawn as it doesn’t dissolve
in the water.
As the solvent (water) soaks up the
paper, it carries the mixtures with it.
Different parts of the mixture will move
at different speeds and they will
separate.
Formula
Calculation
Mr
Water
H 2O
1 + 1 + 16 =
18
Sodium
hydroxide
NaOH
23 + 16 + 1 =
40
Magnesium
Mg(OH)2
hydroxide
24 + 16 + 16 + 1 + 1 = (remember that there
are two of each atom inside the brackets)
Relative Formula Mass: Find the mass of each
atom and add up all the masses in the compound.
Key words:
1. Conservation of Mass: Atoms are not lost or gained, just
rearranged
2. Relative Formula Mass (Mr): The total mass number of
all atoms in a compound
3. Limiting reactants: A reactant that is used up in a
chemical reaction and stops it from continuing
4. Chromatography: A technique where a mixture is
separated
For example:
• Magnesium reacts with
hydrochloric acid.
• When the reaction is over:
Magnesium is the limiting reactant
if it is all gone at the end and the
hydrochloric acid is still left.
58
The Avogadro number
One mole of atoms contains 6 x
1023 atoms, no matter what
element it is.
Moles of elements
One mole of any element
has a mass in grams that
is equal to its relative
atomic mass.
Mole calculations
This equation shows how relative formula mass,
number of moles and mass are related:
number of moles = mass ÷ relative formula mass
Limiting reactants
• A reaction stops when all the particles
of one of the reactants are used up.
• In a reaction involving two reactants:
• The limiting reactant is the one that is
all used up at the end of the reaction
More Y8 5.3 Quantitative
Chemistry
Name of Chemical
Test
Oxygen
A glowing splint will relight in a test tube of oxygen
Hydrogen
A lit wooden splint goes pop when put in a test tube of hydrogen gas
Carbon dioxide
Limewater will turn milky and a lit splint will go out in the presence
of carbon dioxide
Chlorine
Damp blue litmus paper turns read in the presence of chlorine
Key words:
1. Reversible reaction: A reaction that can go backwards
and the products be converted back into the reactants
2. Exothermic reaction: A reaction that releases heat so
feels hot
3. Endothermic reaction: A reaction that takes in heat
from its surroundings to feels cold
Reversible reactions
• Many reactions, such as burning fuel, are irreversible – you cannot go
backwards to get what you started with.
• In a reversible reaction, the products can react to produce the
original reactants again.
• It can go backwards to get back what you started with.
• When writing chemical equations for reversible reactions, we do not
use normal arrow. Instead we use this:
• For example:
ammonium chloride
•
•
•
Endothermic reaction
Energy is taken from the
surrounding for the chemical
reaction and feels cold e.g. an
ice pack
ammonia + hydrogen chloride
The equation shows that ammonium chloride (a white solid) can break
down to form ammonia and hydrogen chloride.
It also shows that ammonia and hydrogen chloride (colourless gases)
can react to form ammonium chloride again.
It can go backwards!
Exothermic reaction
Energy is transferred as heat
to the surrounding during the
reaction e.g. a hand warmer
Y8 6.7 Atomic Structure
Half life
The time taken
for half of the
radioactivity to
decay
Particle
Charge
Mass
Electron
-1
0
Proton
+1
1
Neutron
0
1
Rules:
1. Mass number = protons + neutrons
2. Atomic number = no. of protons
3. no. of electrons = no. of protons
Key words:
1. Isotope: Same number of protons but different number
of neutrons
2. Alpha radiation: The least penetrative radiation,
stopped by paper. Alpha particle consists of 2 protons
and 2 neutrons
3. Beta radiation: Stopped by paper. Beta particle
consists on an electron
4. Gamma radiation: The most penetrative radiation,
stopped by lead. Gamma radiation causes a high
frequency electromagnetic wave to be emitted.
5. Half life: The time taken for half of the radioactivity
to decay
In gamma a high frequency
EM wave is emitted
Alpha () – an atom decays into a new
atom and emits an alpha particle (He) (2
protons and 2 neutrons)
Beta decay – a neutron turns
into a proton and releases and
electron
The mass
number
decreases by 4
The proton
number
decreases by 2
Bohr 1913
Electrons were in orbitals
round a positive nucleus
Isotope
The same elements and have the same
number of protons but different
numbers of neutrons
Democritus
400 BC
Came up with
the idea of
atoms
Thomson 1897
Plum pudding
model, positive
ball and
negative
electrons
Rutherford
1911
Dense
positive
nucleus
which made
up most of
the mass
Dalton
Thought the atom was a
solid dense ball