🌿
SCIENCE
BIOLOGY
Unit 1
🔬🥼🦠👨‍🔬
1.1 Photosynthesis
Plants make food by photosynthesis
-​ In photosynthesis plants use:
●​ Water
●​ Carbon dioxide
●​ energy
The energy in sunlight is captured by a green pigment, called chlorophyll
*WORD EQUATION:​
Water + carbon dioxide → glucose + oxygen
1.2 More about photosynthesis
On warm sunny days, plants can make more carbohydrates than they need.
-​ Plants store carbohydrate as starch inside the chloroplast.
*TESTING FOR STARCH
➔​ 1. Place a leaf in boiling water to break the cell membranes - the starch is in the
cells.
➔​ 2. Place the leaf in hot alcohol - this removes chlorophyll to see color change
➔​ 3. Add iodine to the leaf - this highlights the starch by going black
Chloroplasts also need plenty of water and carbon dioxide
-​ Carbon dioxide diffuses into the leaf from the air
●​ It moves into holes called stomata
MINERALS AND GROWTH
Farmers add fertiliser to their fields because it makes the crops grow larger and
produce a higher yield.
●​ Plants get minerals from the soil, but sometimes there is not enough
➔​ Magnesium is needed to make chlorophyll
●​ Plants use nitrate to change carbohydrates to protein
➔​ Proteins are essential for making new cells
➔​ Nitrogen is also needed to make chlorophyll
1.4 Climate change
Carbon dioxide and methane are ‘greenhouse gases’
Carbon dioxide levels in the atmosphere are increasing
➔​ This is affecting the climate on Earth
Climate is the long-term pattern of temperature, wind and rainfall on Earth
-​ In the warm periods, there was no ice at all, even at the poles
-​ In the colder periods, called ice ages, there was ice at the poles
The dinosaur asteroid caused a mass extinction
-​ Up to 75% of all the species become extinct because of the asteroid collision
Objects in space that are smaller than an asteroid are called meteoroids
-​ When meteoroids enter Earth’s atmosphere they are called meteors
-​ The parts of meteoroids that collide with Earth are called meteorites
●​ For the last 200 years or so, our climate has been fairly stable,
●​ Now, however, the mean (average) temperature on Earth is increasing.
Impact of climate change
●​ More extreme weather events
●​ Less predictable rainfall
●​ Rising sea levels
-​ Ice melting
-​ Water expand due to heat
Unit 4
4.1 Plants and water
Root hair cells provide a big surface through which water and mineral ions can be
absorbed into the plant
In the centre of the root are xylem vessels.
-​ These are the water transport system of the plant
4.2 Transpiration
When water arrives at a leaf, it moves from the xylem into the leaf cells
Most of the liquid water soaks into the cell wall, changes to water vapour and
evaporates
Water vapour can diffuse through the stomata and into the air.
The loss of water vapour from leaves is called transpiration
Why plants need water
●​ Water for support
●​ Water for transport
●​ Water for cooling
●​ Water for photosynthesis
4.3 Excretion in humans
What is excretion?
Excretion means getting rid of waste materials
●​ Proteins in food are broken down to smaller molecules inside the digestive
system
●​ These small molecules go into the blood
●​ If we have more protein than we need, the liver changes the smaller molecules
into urea
●​ The urea is taken away in the blood
●​ As blood flows through the kidneys, the urea is removed (filtered)
●​ The kidneys also remove excess water from the blood
●​ The urea dissolves in the water to make urine
●​ The urine flows down a tube (ureter) to the bladder
●​ The urine is removed from the body through another tube, called the urethra
●​ The excretory system is also known as the renal system
Workbook:
1)​ kidneys
Renal
Urea
Water
urine
4.4 Keeping a fetus healthy
A fetus is a baby before it is born
-​ The fetus relies on its mother to supply all the things that it needs, and to remove
substances it excrete
-​ The substances that the fetus needs, diffuse from the mother’s blood to the
fetus’s blood.
-​ The substances that the fetus needs to excrete diffuse in the opposite direction
When she is pregnant, a woman needs to eat a balanced diet
She needs to eat a little bit more than usual
Protein
●​ Produce new cells and grow
Mother needs extra protein to make extra haemoglobin
Carbohydrate
●​ Supplies energy for respiration
Vitamins and minerals
●​ Iron is needed to make haemoglobin
●​ Calcium to grow strong bones
Smoking cigarettes
-​ Tobacco smoke contains carbon monoxide, nicotine and tar
-​ Carbon monoxide reduces the amount of oxygen that haemoglobin can transport
-​ Nicotine is an addictive drug. It can damage blood vessels
Drugs
-​ A drug is something that is taken into the body, and that affects the way the body
works
-​ Most drugs that a pregnant woman takes will go into her fetus’s blood. So the
fetus is taking the drug, too.
Unit 7
7.1 Chromosomes, genes and DNA
The nucleus of every cell contains threads called chromosomes.
●​ Human cells have 46 chromosomes
●​ We have two of each kind of chromosomes
●​ Each chromosome is made up of hundred of different genes
●​ Each gene controls a characteristic in the organism
Chromosomes are made of chemical substance called DNA
This means that genes are also made of DNA
●​ The shape of DNA is called a double helix
Cell > Nucleus > Chromosome > DNA > Gene (segment of DNA)
Workbook answer:​
3)
●​ Chromosome: long threads made from DNA
●​ Gene: part of DNA that controls our feature ( eye colour)
●​ DNA: long chain that makes chromosomes
7.2 Gametes and inheritance
Sperm cells and egg cells are specialized cells known as gametes
Sperm cell
Egg cell
A male gamete
A female gamete
Smaller than egg cell
Larger than sperm cell
Has a tail and can swim
Cannot move
Does not contain many food reserves
Contains food reserves
Gametes have only one set of chromosomes (23)
The joining of a sperm and egg cell is called fertilisation
The new cell that is formed is called a zygote
A person with two X chromosomes, XX, is female
A person with one X chromosome and one Y chromosome, XY, is male
●​ All egg cells contain one X chromosome.
●​ But sperm cells can have either X or Y chromosomes.
Inheritance
Inheritance means passing on DNA from parents to offspring
7.3 Variation
The differences between individuals belonging to the same species are called
variation
Each gene is different because its DNA is different
Differences in the DNA of organism within a species are called genetic
differences
🧪
CHEMISTRY
Unit 2
2.1 Atomic structure and the Periodic Table
Atomic number is the amount of protons in an atom
Mass number is how many protons and neutrons in the atom
-​ Protons have a positive charge
-​ Electrons have a negative charge
Density is given using the unit g/cm3
Electrons are arranged in electron shells around the nucleus
This is the electronic structure
The order is 2, 8, 8
The electrons are held in place by electrostatic forces
Workbook answer:
1)​ 12
2)​ 14
3)​ Aluminium
4)​ Neon
5)​ Atomic number = 5
Mass number = 11
Number of protons = 5
Number of neutrons = 6
Number of electrons = 5
6)​ A. 6
B. 6 C. 6
2.2 Trends in Groups within the Periodic table
Columns in the Periodic Table are called groups
-​ The first group, is known as the alkali metals
-​ The halogens are another group in the Periodic Table, Group 7
-​ The noble gases, group 8
●​ They are inert (unreactive) and do not from compounds
Workbook answer:
2.2A
1)​ Number increase
2)​ Number increases
3)​ Atomic number = 11
Mass number = 23
Number of protons = 11
Number of neutrons = 12
Number of electrons = 11
4)​ 2, 8, 1
5)​ Have 1 electron on the outer shell
6)​ Atomic number = 19
Mass number = 39
Number of protons = 19
Number of neurons = 20
Number of electrons = 19
7)​ 2, 8, 8, 1
8)​ 1 electron on the outer shell
9)​ Different size, different number of shell
2.2B
1)​ A column
2)​ A: size increases as we go down melting/boiling point increases. Reactivity
decrease
B: higher
C: liquid, boiling point will be more than 59 degree celsius
D: lower, iodine is higher in the group
E: less reactive
2.3 Why elements react to form compounds
The shell with the highest energy level is on the outside of the atom - the outermost
electron shell
-​ Atoms are more stable when the outermost electron shell is full
Sodium reacts with other elements by losing an electron, the sodium atom forms an ion
(Na → Na+)
-​ The sodium ion is more stable
In an ionic bond there is an attraction between the positively charged ion and the
negatively charged ion
Potassium loses the electron in the outermost electron shell more easily than sodium or
lithium can lose theirs.
The electron in the outermost electron shell of potassium is furthest away from the
protons so it is easier to overcome the electrostatic force.
Flourine gains an electron in the outermost electron shell more easily than chlorine
(bigger atom)
The electron in the outer shell of a small atom is closest to the protons, so an extra
electron is attracted more easily than in a bigger atom
Ionic compounds are those that are made from ions when a metal reacts with a
non-metal
Covalent bond
This type of diagram is know as a dot and cross diagram
This type of chemical bond where electrons are shared is called a covalent bond
Covalent molecules are formed when atoms of different non-metals join together
2.4 Simple and giant structures
The ions in sodium chloride make a giant structure known as a lattice
-​ Sodium chloride forms crystals with a regular shape
Giant covalent structures
-​ The forces holding the molecules together are very strong
-​ The forces between the molecules are weak
The forces between the molecules are called intermolecular forces
Giant structures of carbon
The carbon atoms in diamond form a giant structure
* These large structures are called macromolecules (only covalent molecules)
Graphite has layers, which can easily slide over one another.
-​ The covalent bonds between the carbon atoms in the layers are strong
-​ The bonds between the layers are weak so the layers slide over each other very
easily
Melting and boiling points
-​ Ionic substances have a very high melting points and boiling points, because it
has strong electrostatic force between ions
-​ Covalent substances made from simple molecules have low melting points and
boiling points
Conducting electricity
-​ Ionic compounds will conduct electricity if they are dissolved or if they are
melted
-​ Covalent substances made from simple molecules do not conduct electricity
Unit 5
5.1 Reactivity and displacement reactions
The reactivity series has the most reactive metals at the top.
Iron is more reactive than the copper that it has ‘pushed out' from the copper sulfate
and has reacted to form iron sulfate
This ‘pushing out’ is called displacement, so this type of reaction is called a
displacement reaction.
A more reactive metal can replace a less reactive metal in a salt
5.2 Using the reactivity series and displacement reactions
It is possible to use displacement reactions to help identify an unknown metal
A chemical reaction that releases energy is an exothermic reaction
The iron oxide and aluminum powder react
This reaction is called the thermite reaction
Carbon will displace zinc, iron, tin and lead from their ores
●​ An ore is a rock that contains a metal compound
This displacement reaction is still carried out, but on a large scale, in a blast furnace
The word equation for this reaction is:
-​ Iron oxide + carbon → iron + carbon dioxide
5.3 Salts
All acids contain hydrogen
Name of acid
Formula
Salts formed from the acid
Hydrochloric acid
HCL
chlorides
Sulfuric acid
H2SO4
sulfates
Nitric acid
HN03
nitrates
Salts made from carbonic acid are called carbonates
Salts formed using citric acid are called citrates
The general equation for the reaction of metals with acid is:​
Acid + metal → salt + hydrogen
Some metals will not react with acids to make salts.
The general equation is:​
Metal oxide + acid → salt + water
5.4 Others ways of making salts
Carbonates can be formed by the reaction of a metal with carbonic acid
The general equation:
Acid + carbonate → salt + water + carbon dioxide
CO2 will make line water cloudy
When an acid is neutralised by an alkali, a salt is produced.
The general equation for neutralisation:
Acid + alkali → salt + water
Alkalis and bases
Metal oxides are called bases.
Soluble metal bases form alkalis when they dissolve in water
Some metals oxides are not soluble in water, so they do not form alkalis.
Workbook:
5.4 A
1)​ It reacts to make copper chloride, water and CO2
2)​ Copper carbonate
3)​ Copper chloride
4)​ Evaporate the water
5)​ Be careful with the boiling water
6)​ Wear goggles
7)​ Copper carbonate + hydrochloric acid → copper chloride + water + carbon
dioxide
5.4 B
1)​ Hydrochloric acid
2)​ Burette full of acid, add universal indicator, add drop of acid until indicator turns
green
3)​ Don’t spill acid
4)​ Indicator turns green
5)​ evaporate liquid
6)​ Potassium hydroxide + hydrochloric acid → potassium chloride + water
7)​ KOH + HCL → KCL + H2O
5.5 Rearranging atoms
If no atoms are gained or lost during a chemical reaction, then no mass is gained or lost
either.
The mass you begin with is the mass you end with. This is the law of conservation of
mass
Energy is used to break bonds in the reactants and energy is released when new bonds
are formed in the products
●​ When less energy is needed to break bonds in the reactants than is released
when bonds form in the products.
➔​ This is an exothermic reaction
➔​ It releases heat energy
●​ When it takes more energy to break bonds in the reactants than is released when
the bonds form in the products.
➔​ This is called endothermic reactions
➔​ They take in energy
Unit 8
8.1 Measuring the rate of reaction
The rate of reaction is a measure of the speed of a reaction
The rate of reaction can be measure by finding:
-​ How much of one of the products has been made in a given time
-​ How much of a reactant has been used up in a given time
To collect the gas, attach a syringe to the top of a flask so that no hydrogen can
escape
You can measure the volume of gas produced
A graph of the rate of reaction can be used to measure the rate of reaction at
any given time
The steeper the slope, the faster the reaction
The particles of the reactants have to collide with enough energy to react
At the start of the reaction there are a lot of particles that have not reacted.
➔​ Collisions happen frequently
As the particles react, the number of particles that have not reacted gets lower
Eventually, all the pảiticles have reacted
The reaction has finished
8.2
PHYSICS
Unit 3
⚖️
3.1 Density
When calculating the volume of a regular block of material, we multiply the lengths of
the sides
If the shape is irregular, we find volume using the displacement method
Density means mass per unit volume
density = mass/volume (g/cm^3)
-​ if something is more dense than water, it will sink
-​ if something is less dense than water, it will float
Liquids of different density will form seperate layers
Gases are less dense than liquids
When a gas is compressed, the density of the gas increases.
3.3 Conservation of energy
When energy is conserved, we mean that the total quantity of energy stays the same
Sanky diagram:
In physics, a system is something that has been chosen to study (normally, for energy
transfer
Law of conservation of energy
Energy cannot be created or destroyed, only changed from one form to another
Workbook answer:
3.3A
1)​ the quantity of energy will stay the same
2)​ Energy input to the lamp equals energy output from the lamp
3)​ 100J
4)​ 3500J
3.3B
1)​ Energy cannot be created or destroyed, only change
2)​ All electrical energy will be changed to light and thermal energy
3)​ When she is playing sport she used more energy so she needs more energy input
4)​ 100 - 65 = 35%
3. 4 Moving from hot to cold
Dissipation is used to describe energy that spreads out and becomes less useful
The rate of thermal energy transfer increases when the temperature difference between
the hot place and the cold place increases
3.4A
1)​ Lower temperature
3.4B
1)​ Thermal energy moves from hot object to the cold object
3.5 Ways of transferring thermal energy
Solids expand when heated
Liquids expand when heated
Gases also expand when heated
Conduction
This process happens in all solids
Conduction does not work in liquids or gases
Conduction cannot happen in a vacuum
Convection
Heat can be transferred in liquids or gases by convection
A convection current causes heat to be transferred through the liquid
Convection cannot happen in a solid
Convection cannot happen in a vacuum
Radiation
Heat can be transferred by radiation
Because no particles are involved, radiation can work in a vacuum
Radiation can also pass through transparent solids, liquids and gases
The best emitters and absorbers:
●​ Are dull
●​ Are black
●​ Have a large surface area
3.6 Cooling by evaporation7
Some particles in water move faster than others
-​ They have more energy
-​ Some of these particles have enough energy to escape from the surface and
become gas
When particles with the highest energy escape, this will lower the average energy of the
water
Different liquids have different forces holding the particles together
Unit 6
6.1 Loudness and pitch of sound
Loudness depends on two variables:
●​ How much the object is vibrating
●​ How far away the vibrating object is
An oscilloscope displays graphs of sound waves
The maximum distance (forward or backwards) that particles move is called the
amplitude
As the amplitude increases, the loudness increases
The faster the vibrations, the higher the pitch of the sound
The speed of vibrations is measured by the number of vibrations per second
-​ This is called frequency
-​ Frequency is measured in hertz or Hz
6.2 Interference of sound
Interference can only happen when the waves are of the same type
The waves must have the same frequency and the same amplitude
●​ Waves will reinforce when the peaks and troughs fit together
-​ The amplitudes are added together
-​ The frequency does not change
●​ For two sound waves to cancel completely, their frequencies AND amplitudes
must be the same.
-​ The amplitude of the sound wave becomes zero
-​ Peak will line up with the trough
6.3 Formation of the Moon
Collision theory for formation of the moon
The collision theory (commonly called the giant impact hypothesis) is another theory of
how the Moon was formed
The collision theory refers to a collision happened relatively soon after the formation of
the Solar System
A newly formed planet (about the size of Mars) collided with the newly formed Earth
●​ Called Theia
The theory states that Earth was formed from the two planets joined together
The moon was formed from rocks and dust being pulled together by gravity.
Evidence that supports the collision theory:
●​ The Moon has a small iron core, similar to Earth
●​ The composition of rocks on the Earth and the Moon are the same
●​ Samples of rock from the Moon show that its surface was once molten
●​ The Moon is less dense than the Earth
Evidence that contradicts the collision theory:
●​ The surface of the Earth does not appear to ever have been molten, A collision
that formed the Moon would have caused the surface of the Earth to melt. The
surface would have late solidified
●​ Venus has no moon. Collisions in the early years of the Solar System would have
been common and scientists would have expected Venus to have a moon
formed in the same way
●​ The composition of rocks on the Moon would be expected to be more similar to
rocks on Theia than rocks on Earth. In fact, the composition of the Moon is more
similar to Earth
6.4 Nebulae
Nebulae are clouds of dust and gas in space
●​ They are mostly hydrogen and a smaller quantity of helium
●​ Most nebulae are very large (10 000 times bigger than the solar system)
Some types of nebulae act as stellar nurseries
●​ Stellar nurseries: where stars are born
●​ In a stellar nursery, the dust and gas can start to collapse together under the
force of gravity
-​ The pressure inside the new star gets very large
-​ This causes heat
-​ The heat can cause atoms to react, causing the new star to give out heat
and light
Workbook answer:
1.​ Asteroid, moon, star, nebula
2.​ A nebulae contain dust and gas
Nebulae are different shapes
3.​ Hydrogen
4.​ Supernova remnant
5.​ Pleiades
6.​ Emissions nebula
7.​ Emit large quantity of energy, they appear bright
6.5 Tectonics
The high temperature of the inner core is due to thermal energy leftover from the
formation of the Earth.
This hotter, less dense fluid in the mantle rises towards the crust, cools and sinks again,
resulting in a convection current
As the convection currents move, the tectonic plates that make up the crust are pulled
along
-​ The movement of the tectonic plate is slow (0.6 and 10cm per year)
Evidence for tectonic plates
1.​ Scientists say that this continental jigsaw appearance is evidence for tectonic
plates.
There is a hypothesis that there was once only one large continent that
eventually separated
2.​ Fossil record
●​ Scientists have found fossils of plants and animals in rocks of similar age.
●​ These rocks were on the coast of different continents
●​ This suggests that the continents were once joined
●​ For example, fossils of Mesosaurus, a freshwater reptile have been found
both in Brazil and western Africa.
3.​ Magnetic crystals
●​ Magnetic material in molten rocks line up with the Earth’s magnetic field
●​ They stay in this alignment when the rock solidifies
●​ The Earth's magnetic field reverses about every 1 million years
●​ Rocks either side of mid-ocean ridges show symmetrical patterns.
●​ This suggests the new rock forms and pushes the tectonic plate apart.
4.​ Earthquakes/volcanoes
●​ There are more earthquakes and volcanoes at the tectonic plate
boundaries
Unit 9
9.1 Parallel circuits
●​ In a series circuit, there is only one path. The current is the same all the
way around
Parallel circuits
In a parallel circuit, there is more than one path.
●​ The current through the cell is equal to the total current in all the branches
●​ If a component in one branch stops working, the other branches are not
affected
9.2 Current and voltage in parallel circuits
The voltages across each component in a series circuit must add up to the
voltage of the supply.
Adding more components in a series circuit will decrease the current.
Increasing the number of cells in a series circuit will:
●​ Increase the current in the circuit
●​ Increase the voltage across each component
The voltages across each of the branches of a parallel circuit are equal to the
voltage of the supply.
Adding more branches to a parallel circuit means the current through the cell
increases
Adding cells to a parallel circuit increase voltage:
●​ Increase the voltage across each branch
●​ Increase the current through the cell
●​ Increases the current through each branch
9.3 Resistance
Resistance is a measure of how easy/difficult it is for electrons to move through
a material.
●​ Conductors have very low resistance
●​ Insulators, have very high resistance
Resistance is measure in units called ohms
Resistance slows the flow of electrons, so lowers current = higher resistance
Resistors
A resistor is a component designed to have a known resistance
9.4 Practical circuits
Variable resistors
It is useful to be able to change the resistance in a dimmer switch for a lamp.
Workbook answer:
9.4A
1)​
2)​ 1-50
3)​ A. the current will decrease
B. brightness decrease
9.4B
1)​ Variable resistor can change resistance, fixed cannot
2)​