Science Notes

UNIT 2 - PERIODIC TRENDS

Isotopes

Atoms with the same number of protons but different number of neutrons

Ionic and Covalent Bonds

Covalent

• Bond between non-metals
• Atoms are held by covalent bonds
• Exists as individual molecules
• Example; sugar

Ionic

• Bonds formed when metals transfer electrons to non-metals
• Metal + Non-Metal
• Atoms are held by ionic bonds
• When naming ionic compounds identify the cation then anion
• Example; sodium chloride

Types of Ions

Anion

• Negative
• Gains electrons
• Non metals can gain electrons

Cation

• Postive
• Has more protons than electrons
• Formed by losing electrons

Group 1 elements - Alkali Metals

• Very reactive
• Soft, shiny, and can easily be cut
• Good conductors of heat and electricity
• Reacts vigorously with water
• They have one valence electron
• Their melting and boiling points decreases down the group
• They are relatively light so their density increases down the group
• Reactivity increases down the group
• Lithium, Sodium, Potassium, Rubidium, Cesium, Francium

Group 2 elements - Alkaline Earth Metals

• Very reactive
• Soft, silver metals that are less metallic in nature compared to group 1
• They have 2 valence electrons
• Hard and more dense than group 1
• Electrical conductors
• All react with water to form hydrogen and hydroxides, but not as vigorously as group 1
• Reactivity increases down the group
• Beryllium, Magnesium, Calcium, Strontium, Barium, Radium

Group 7 elements - Halogens

• They are non metals
• Poor conductors of heat and electricity
• Crumbly and brittle
• Melting and boiling points are low
• They have 7 valence electrons
• Most reactive family of nonmetals
• Reactivity decreases down the group
• Fluorine, Chlorine, Bromine, Iodine, Astatine

Periodic Trends

Atomic Radius

The distance between the nucleus and the valance electrons

Factors affecting atomic radius :

• Nuclear charge because more protons pull more electrons closer, reducing the atomic size
• Electron shielding as the inner electrons blow nuclear attraction towards the outer shells, increasing the atomic size

Across the Period :

The atomic radius decreases across the period because the number of protons increase, thus the nuclear charge also increases, making a stronger positive charge. A stronger positive charge attracts electrons closer to the nucleus, reducing the atomic number

Down the Group :

The atomic radius increases down the group as the number of shells added increases, thus increasing the distance between the nucleus and the valance electrons. The inner electrons shield the outermost electrons from the nuclear attraction, weakening the pull and allowing the atomic radius to expand

Ionization energy

The tendency to remove an electron

Factors affecting Ionization Energy :

• Nuclear charge because a stronger reaction requires more energy to remove an electron
• Atomic radius because a larger atom as a weaker attraction, requiring less energy
• Electron Shielding because more shielding lowers the attraction, making it easier to remove electrons

Across the Period :

Ionization energy increases across the period because atoms have a higher nuclear charge and a smaller atomic radius, thus more energy is required to remove the valence electrons.

Down the Group :

Ionization energy decreases down the group because the atomic radius increases, and electron shielding allows the valence electrons to have less attraction towards the nucleus, requiring less energy to remove valence electrons.

Electronegativity

An atom's ability to hold and attract shared electrons in a chemical bond

Factors affecting electronegativity :

• Nuclear charge because more protons increases the attraction for shared electrons
• Atomic radius because smaller atoms pull bonding electrons more strongly
• Electron shielding because more inner electrons weaken the attraction

Across the Period

Electronegativity increases across the period because the atom becomes smaller, and the nuclear charge increases. This allows the nucleus to exert a stronger pull on bonding electrons

Down the Group

Electronegativity decreases down the group as it has a larger atomic radius, increasing the distance between the nucleus and bonding electrons

Electron Affinity

The tendency to gain an electron

Factors affecting Electron Affinity :

• Nuclear charge because a stronger charge attracts extra electrons
• Atomic radius because a smaller atom attracts atoms more strongly
• Electron repulsion because adding an electron to an already negative electron is difficult

Across the Period

Electron affinity increases across the period as the nuclear charge increases, and atoms become easier to gain as the valance electrons increase

Down the Group

Electron affinity decreases down the group as the atomic radius increases and the nucleus is further from the incoming electrons. The weaker attraction makes it less favourable to gain new electrons

Chemical Reactivity

How easily an element undergoes a chemical reaction

Factors affecting Chemical Reactivity :

• Atomic radius because larger atomic radius in metals makes it easier to lose electrons, increasing reactivity, while in non-metals a smaller radius allows a stronger electron attraction
• Electron affinity because non-metals with high electron affinity readily gains electrons, increasing reactivity

Across the Period

Metals become less reactive across the period as their ionization energy increases making it harder to remove an electron. Non-metals become more reactive across the period as their electronegativity and electron affinity increases, making them more eager to gain electrons

Down the Group

Metals become more reactive down the group as their atomic radius increases, making it easier to lose electrons. Non-metals become less reactive down the group as the increase in atomic radius weakens their ability to attract additional electrons

Electron Configuration

• If an electron is given away, the element becomes positive (anion) and vice versa (cation)
• Ionic compound is when an atom gives an electron, and another one takes it. Between non-metal
• Covalent compound is formed when 2 same element atoms share an electron, in non-metals
• Valency means the number of electrons needed by an element to become stable. The outer shell of an element contains electrons known as valence electrons.

UNIT 3 - FORCE AND PRESSURE

Types of Forces

• Contact
• Mechanical
• Physical
• Non Contact
• Magnetic
• Gravational
• Electrostatic

Friction

• It is the force which acts on an object in the opposite direction
• It allows you to write with pens and hold objects
• It is harmful as it produces lots of heat and sounds
• You can reduce friction by making the surface smooth or adding wheels

Air Resistance

• It is the friction between a moving object and the air which it moves in
• Air resistance increases with speed
• Terminal Velocity is when the downward force of gravity is balanced by the upward force of air resistance

Momentum

• It is the quantity of a moving object or it can be called “mass in motion”
• Momentum = Mass * Velocity or p = m * v
• The unit for momentum is kilogram-meters per second (kg m/s)

Moment

• When a force is applied and a turning effect is produced
• In equilibrium the sum of the clockwise moments is equal to the sum of the anticlockwise moments.
• Moment = Force x Distance from Pivot

Scalar and Vector Quantities

• Scalar : Quantities which have magnitude without directions. For example; mass, speed, direction, work, energy, temperature
• Vector : Quantities which have magnitude and direction. For example; velocity, force, displacement, pressure, momentum

Newton's Laws of Motion

Newton's First Law

• An object in motion stays in motion and an object at rest stays at rest unless an external force acts upon it
• There are 3 types of inertia; motion, rest, and direction

Newton’s Second Law

• Acceleration is dependent based off of 2 factors, mass and force
• The more acceleration the more force
• Greater the mass lower the acceleration
• By this information we can deduce the formula F=MA

Newton’s Third Law

• Every object has an equal and opposite reaction

Levers

• Effort : The part of the lever that utilizes the input force to move
• Load : The output energy
• Fulcrum : The pivot point of the lever

1st Class

• The fulcrum is in the middle and the effort and load are on the sides
• It increases mechanical advantage
• Examples; scissors, seesaws, handpumps

2nd Class

• The load is in the middle and the fulcrum and effort are on the sides
• Multiplying the applied force
• Examples; wheelbarrow, bottle openers, suitcases

3rd Class

• The effort is in the middle and the fulcrum and load are on the sides
• Accelerates our work
• Examples; shovels, tongs, excavators

Mechanical Advantage

• It is the measure of how much a machine can make our work easier
• Ideal Mechanical Advantage : It is a machine which does not take friction into consideration
• Actual Mechanical Advantage : It is a machine which does take friction into consideration

Pressure

Pressure is defined as the physical force exerted on an object

Effect of Pressure

• Gas : Increasing the pressure reduces the volume on gases
• Temperature : Higher pressure increases the temperature
• Fluid Flow : Fluids move from higher pressure to lower pressure areas
• Hydraulic Systems : Pressure is used in machines like hydraulic brakes and lifts

Solid Pressure

Smaller the surface area, the greater the pressure

Liquid Pressure

• The force exerted by a liquid per unit area
• It increases with depth
• Liquid pressure is exerted equally in all directions
• A denser exerts more pressure rather than a less dense one
• P = gh

Hydraulic Systems

Hydraulic systems use pascal's principle, which states that pressure applied to an enclosed fluid is transmitted equally in all directions

In hydraulic systems, Pascal's Principle is used to multiply force. When a small force is applied to a small piston (A), the pressure is transmitted through the incompressible fluid, and a larger force is exerted on the larger piston (B). This principle is widely used in hydraulic brakes, hydraulic lifts, and hydraulic presses, where small applied forces can generate much larger output forces to lift heavy loads or stop vehicles.

Applications of Liquid Pressure

• Dams : They hold back large amounts of water, and the pressure increases with depth. To withstand this, dams are built thicker towards the base which resists strong water pressure
• Submarines : Since submarine divers go deep underwater the liquid pressure increases so submarines are built with strong materials like metal

Gas Pressure

• Gas pressure is the force exerted by gas molecules when the collide
• Higher the temperature, higher the pressure
• Decreasing the volume increases the pressure
• The more molecules present, the more pressure

Pascal's Law

• Pressure applied to an enclosed fluid is transmitted equally in all directions
• This formula is able to represent this statement P = F/A

Gas Laws

Boyle's Law

• When the temperature is constant, if the pressure increases then the volume decreases and vise versa
• For example, when a scuba diver goes deep into the ocean the pressure increases so their oxygen tank will compress
• The formula is p1v1 = p2v2

Charles Law

• When the pressure is constant, if the temperature increases then the volume also increases and vise versa
• For example, when a hot air balloon heats up the volume also increases
• The formula is v1/t1 = v2/t2

Gay - Lussac's Law

• When the volume is constant, if the temperature increases then the pressure increases
• A pressure cooker increases pressure as the temperature increases
• The formula is p1/t1 - p2/t1

UNIT 4 - BLUEPRINT OF LIFE

Cell Theory

1. All know things are made up of one or more cells
2. Cells come from preexisting cells through division
3. Cells are the basic unit of structure and function

Structure of Cell

Plasma Membrane

• Structure : Made up of 2 layers of lipid molecules in which protein molecules are floating
• Function : Regulates entry and exit of substances, maintains shape and size

Cell Wall

• Structure : Tough, rigid, made out of cellulose
• Function : Controls cell expansion, provides shape

Nucleus

• Structure : It has a double layered covering (nuclear membrane)
• Function : Controls all cell activities, stores hereditary information in genes

Cytoplasm

• Structure : Jelly like substance
• Function : Holds organelles in place

Endoplasmic Reticulum

• Structure : Has smooth and rough endoplasmic reticulum
• Function : Synthesizes lipids and proteins

Golgi Body

• Structure : Formed by 5-8 membranous sacs
• Function : Delivers synthesized materials, forms lysosomes

Lysosome

• Structure : Small and spherical, found throughout cytoplasm
• Function : Protects cell by destroying pathogens

Vacuoles

• Structure : Filled with waste material, they are found more in plants compared to animal cells
• Function : Stores waste products

Mitochondria

• Structure : Small, rod shaped
• Function : Powerhouse of the cell, synthesize ATP

Chloroplast

• Structure : Double membrane-bound organelle, only found in plant cells
• Function : Convert light energy into chemical energy, gives leaves their green colour

Prokaryotes vs Eukaryotes

Animal vs Plant Cell

Specialised Cells

Red Blood Cells

• Contains haemoglobin
• Has no nucleus
• Flexible to fit through capillaries

White Blood Cells

• Engulfs pathogens
• Can change shape
• Kills microbes and bacterias

Ciliated Epithelial Cells

• Traps dust and bacteria
• Has tiny hairs called cilia
• Found in respiratory system

Muscle Cells

• Move by contracting and expanding
• Contains lots of mitochondria
• 3 Types : Skeletal, smooth, cardiac

Nerve Cells

• Long
• Sends electrical impulses throughout the body
• Exists in the nervous system

Gametes

• Sperm Cell : Fertilizes the egg
• Ovum : Nourishes blastocysts so an embryo can develop

Root-Hair Cells

• Absorbs water and nutrients
• Present in the root
• Has a large surface area

Palisade Cell

• Helps make food for plants
• Contains lots of chloroplast
• Cell wall and organelles are transparent to let light through

Xylem

• Transports and stores water

Phloem

• Transports sugars and proteins

Mitosis

Interphase

• G1 phase : Cells grows, organelles duplicate, synthesis of proteins
• S phase : DNA replication occurs
• G2 phase : Cell repairs any damage done during DNA replication, cells prepare for mitosis

Prophase

• Chromosomes condense
• The 2 sister chromatids of each chromosome attach to the centromere
• Spindle fibers start to form
• Nucleus disappears

Metaphase

• Chromosomes reached their more condensed state
• Spindle fibres attach to the centromeres of the chromosomes
• Chromosomes align in the middle of the cell

Anaphase

• The centrosomes separate
• The chromatids move to opposite sides of the cell by spindle fibres

Telophase

• Spindle fibres disappear
• New nuclear membrane is formed
• Chromosomes become thinner

Cytokinesis

• The cytoplasm splits forming 2 identical daughter cells

Meiosis

The form of cell division by which gametes, with half the number of chromosomes, are produced

Interphase

• Similar to mitosis

Prophase

• Crossing over occurs which is when (the exchange of genetic material between homologous chromosomes)
• Chromosomes condense
• Nucleolus breaks down

Metaphase

• Tetrads align in the middle of the cell
• Independent Assortment occurs

Anaphase

• Homologous chromosomes move to opposite sides

Telophase

• Each cell contains a haploid

Cytokinesis

• Two haploid cells are formed (daughter cells)

Now the same process which occurs in mitosis takes place

Structure of Flower

Male Part (Stamen)

• Anther : Contains pollen
• Filament: Supports the anther

Female Part (Carpel)

• Stigma : The sticky, top part, where pollen lands
• Style : Stalk like structure that connects the stigma to the ovary
• Ovary : The basal bulged part which contains the female gamete

Sepals

• Protects the flower in its bud stage

Petals

• Attract pollinators to help with pollination

Types of Pollination

• Self Pollination : The transfer of pollen from the anther to the stigma of the same flower or a flower from the same plant.
• Cross Pollination : The transfer of pollen from the anther to the stigma of a flower from a different plant

Fertilisation

• A mature pollen grain contains 2 male gametes has landed on the stigma
• The pollen grain grows a pollen tube which connects the stigma to the ovary
• The male gametes travel through the pollen tube to the ovary
• One male gamete fuses with the female egg which develops into a seed
• The other male gamete attaches to the two cells in the embryo sac forming the endosperm this provides the starchy food for the seed to grow

Genetics and Hereditary

Variation

Differences that exist among individuals in a population, particularly in their traits

Gene

A gene is a segment of DNA that contains genetic material

Allele

An allele is a version of a gene. Each gene may have different forms (alleles), which can result in different traits

Trait

A trait is a characteristic or feature of an organism

Phenotype

The phenotype is determined by both the genotype (the genetic makeup) and environmental influences. It is the physical appearance

Genotype

The genotype is the genetic information of an organism

Homozygous

If a gene has two identical alleles for that gene

Heterozygous

If a gene has two different alleles for that gene.

Mendel's Laws

Law of Segregation

During gamete formation the alleles of each gene segregate from each other so that each gamete formed only contains one allele for each gene

Law of Independent Assortment

Genes for the different traits assort independently of each other during gamete formation

Law of Dominance

Some alleles are dominant while others are recessive, when you have a heterozygous organism on the dominant trait will be shown while the recessive trait is hidden

Sex Determination

• The sperm fertilizes the egg cell to form the zygote
• If the sperm carrying X- chromosome fertilizes an ovum carrying an X chromosome, then the child born will be a girl
• If the sperm carrying Y- chromosome fertilizes an ovum carrying X- chromosome, the child born will be a boy

Selective Breeding

• Selective breeding means to select individuals with the characteristics you want and breed them together
• The process doesn’t stop there though because it’s likely that not all of the offspring will show the characteristics you want so offspring that do show the desired characteristics are selected and bred together
• This process has to be repeated for many successive generations before you can definitely say you have a ‘new breed’ which will reliably show those selected characteristics in all offspring

Genetic Engineering

• Changing the traits of one organism by inserting genetic material from another organism
• The organism receiving the genetic material is said to be ‘genetically modified’
• The DNA of the organism that now contains DNA from another organism as well is known as ‘recombinant DNA

UNIT 5 - CHEMICAL REACTIONS

Exothermic and Endothermic Reactions

Exothermic

• Heat is released
• It usually feels hot and increases temperature
• Examples: burning of fossil fuels, fireworks, explosives

Endothermic

• Takes in heat
• It usually feels cold and decreases temperature
• Examples; ice melting, a kettle boiling

Signs of Chemical Reactions

• Change in colour
• Change in odor
• Formation of precipitate
• Production of new vapours or gas
• Difficult to reverse
• Input or reverse of energy

Law of Conservation of Matter

Matter can neither be created nor destroyed

Vocabulary

• Reactants : The substance that exists before the chemical change
• Products : The new substances that are formed during the chemical change
• Chemical Equation : The reactants and products of a reaction

Displacement Reactions

• It is when a more reactive metal will displace a less reactive metal
• For example, if you drop some magnesium into copper sulphate a reaction will occur since magnesium is more reactive than copper sulfate; if you drop copper sulphate into magnesium no reaction will occur

Types of Chemical Reactions

Synthesis

• Two or more chemicals bond together forming one new substance
• Example; 2Na + Cl2 —> 2NaCl

Decomposition

• One substance breaks down into 2 or more products
• Example: 2H2O —> 2H2 + O2

Single Replacement

• One element replaces another element in a compound
• Example; Zn + 2HCl —> ZnCl2 + H2

Double Replacement

• A compound reacts with another compound to form two new compounds
• Example; AgNO3 + NaCl —> AgCl + NaNO3

Combustion

• A chemical reaction between an organic compound and oxygen gas
• The products in a combustion reaction is carbon dioxide and water
• Example; CH4 + 2O2 —> CO2 + 2H2O

Reactivity Series

Reaction of metals with cold water

• Potassium : It reacts very violently, explodes, hydrogen gas burns
• Sodium : Reacts violently, hydrogen formed may catch on fire
• Calcium : Reacts readily, hydrogen gas is formed
• Magnesium : Reacts very slowly, a few bubbles of hydrogen gas is produced
• Zinc, Iron, Lead, Copper, Silver : No reaction

Reaction of metals with steam

• Magnesium : Reacts violently, magnesium oxide and hydrogen is formed
• Zinc : Burns in steam, zinc oxide and hydrogen is formed
• Iron : Reacts slowly with steam, reaction is very reversible
• Calcium : Reacts violently with steam, producing hydrogen
• Lead, Copper, Silver : No reaction

Reaction of metals with dilute hydrochloric acid

• Potassium, Sodium : Explosive reaction
• Calcium : Reacts violently to give hydrogen and calcium chloride
• Magnesium : Reacts rapidly to give hydrogen and magnesium chloride
• Zinc : Reacts moderately fast to give hydrogen and zinc chloride
• Iron : Reacts very slowly to give hydrogen and iron chloride
• Lead, Copper, Silver : No reaction

Rate of Reaction

Temperature

When you increase the temperature the molecules bounce more, causing them to collide more and have more energy. When you decrease the temperature the molecules are slower and collide less

Concentration

If there is more of a substance there is a greater possibility that the molecules will collide and speed up the rate of reaction. If there is less of something less collisions will occur

Pressure

In gaseous state, when the pressure increases the molecules become closely packed increasing the collision of particles. This means the particles are more likely to react

Surface Area

If the surface area is increased, it speeds up the rate of reaction because more particles are exposed and available to react with

Catalyst

They are substances that change the rate of reaction without being used in the reaction. It is chemically unchanged as the mass of the catalyst at the beginning of the chemical reaction stays the same after the chemical reaction

UNIT 6 - HEAT & TEMPERATURE

Heat

• It is the flow of energy due to temperature differences
• Heat flows from hot objects to cool objects
• Measured in joules

Temperature

• It is the measure of average kinetic energy of particles within an object
• It depends on particle movement
• Measured in degrees (C, F, K)

Measuring Temperature

• 0 degrees celsius is the freezing point of pure water
• 100 degrees celsius is the boiling point of pure water
• -39 degrees celcius is the freezing point for mercury
• 356 degrees is the boiling point of mercury
• -115 degrees is the freezing point of alcohol
• 78 degrees is the boiling point of alcohol

Types of Thermometers

Clinical Thermometer

• Measures body temperature
• Used in clinics
• Temperature range is 35 - 42 degrees celsius

Laboratory Thermometer

• Measures temperatures of an object
• Used in laboratory
• -10 - 110 degrees celsius

Digital Thermometer

• Gives fast results
• Safe as it does not use chemicals

Infrared Thermometer

• Measures surface temperature
• They are non contact
• Use infrared radiation

Food Thermometer

• Verifies if foods are undercooked by measuring the temperature of food

Weather Thermometer

• Measures atmospheric temperature

Mercury Thermometer

• Measures higher temperatures because it has a high boiling point

Alcohol Thermometer

• Measures lower temperatures because it has a low freezing point. The alcohol can vaporise easily when compare to mercury therefore they cannot measure high temperatures

Conduction

• Heat transfer through direct contact
• Involves the transfer of kinetic energy between molecules through collisions
• The heat transfers from a hot body to a cold body
• Example; when you touch a hot kettle

Convection

• Heat transfer through fluids
• The energy transfers through large movements of particles

Daytime (Sea Breeze) : The land heats up faster than the sea. Warm air over the land rises, creating a low-pressure area. Cooler, denser air from the sea moves in, creating a sea breeze (wind from sea to land).

Nighttime (Land Breeze) The land cools down faster than the sea. Warm air over the sea rises, forming a low-pressure area over the water. Cooler, denser air from the land moves toward the sea, creating a land breeze (wind from land to sea).\

Radiation

• Energy travels through electromagnetic waves
• It can transfer energy through an empty space
• Example; radiation from the sun strikes atoms in your body and transfers energy

Evaporation

• Heat transfer when a liquid changes into a gas
• Absorbs heat

Condensation

• The process when water vapour transforms into a liquid
• Reverse action of evaporation

Temperature Conversions

• Celcius To Farenheit : F = 9/5 (c) + 32
• Fahrenheit To Celsius : C = (F - 32) 5/9
• Kelvin To Celsius : C = K - 273
• Celsius to Kelvin : K = C + 273
• Kelvin To Farenheit : F = 9/5 (K - 273) + 32
• Fahrenheit to Kelvin : K = (F - 32) 5/9 + 273