Year 10 Science Yearly Notes /School Certificate

Chemical Reactions:

Reactants: Reactants are the starting substances in the chemical reaction

Products:Products are the substances produced in a chemical reaction

Conservation of Mass: Chemical equations show that atoms are conserved in the reaction; this is known as the conservation of mass

  • Total mass of products = Total mass of reactants

-In a chemical reaction, no atoms are destroyed or created

Acids

Properties of Acids:Acids have certain properties which distinguish it from bases:

  • Taste sour
  • Corrosive
  • React with solid substances

Bases

Properties of Bases: Bases have certain properties which distinguish it from acids:

  • Taste Bitter
  • React with the hydrogen in acids

Indicators

Indicators are substances that can be used to tell whether a substance is an acid or base.

Types of Indicators

-An example of an indicator is litmus paper

  • Acid turns blue litmus paper red
  • Acids do not change the colour of red litmus paper

-Another example of an indicator used for acids is the metal test

  • Acids wear away metals
  • Hydrogen gas is given off while the metal is changing

Universal Indicator & pH:

-pH is a measure of the acidity or basicity of a solution

  • The lower the pH the more acidic the solution
  • Strongly acidic solutions have pH around 0 to 2
  • The higher the pH the more basic the solution
  • Strongly basic solutions have pH around 12 to 14

Chemical Reactions:

- A chemical reaction is when substances combine to form new substances.

  • Indicated by change in colour odour,
  • Exothermic (gives off heat)
  • Endothermic (heat is absorbed)
  • Gas is given off

A Chemical equation: chemical equation summarises the events of a chemical reaction.

Types of chemical reactions:

-Metal/acid Reaction: acid+metalsalt+hydrogen gas

To test for the presence of hydrogen gas, you bring a lit taper next to the gas and it should pop. The name of the salt changed depending on the name of the acid and metal.

I.E: Hydrochloric +Magnesium Magnesium Chloride + hydrogen

-Neutralisation (ACID/BASE reaction) :acid + basesalt +water

I.E: Sulfuric acid + calcium Hydroxide  calcium + water

-Acid/carbonate Reaction: acid+carbonate  salt +carbon dioxide +water

In another words, acid carbonate reaction is when limewater goes from visible to cloudy/turbid.

Nitric Acid + calcium carbonate  calcium nitrate + Co2 +H2o

Types of chemical reactions:

-Combustion: Burning- it is a self-sustaining chemical reaction that occurs at temperatures higher than the surroundings.

-Corrosion: is the eating away of metal so that it loses strength and become unable to do its intended purpose.

-Precipitation: the formation of a solid from 2 solutions.

-Neutralisation: the reaction between an acid and a base

-Decomposition: the breaking of a compound into more simple substances.

The Arrangement of the Periodic Table

-The elements are arranged in the periodic table according to their increasing atomic number

-The elements are arranged in rows and columns

  • Rows are called periods
  • Columns are called groups

Recognising the Elements on the Periodic Table

-Each element is represented in a separate box on the periodic table

-Each box has four different characters:

  • 1. the atomic number
  • 2. the symbol of the element
  • 3. the atomic weight
  • 4. the name of the element

Structure of an atom:

-The atoms of all matter are electrical and are made up of three small subatomic particles:

  • Electrons: which carry negative charges
  • Protons, which carry positive charges
  • Neutrons, which carry no charge.

-Atoms are held together by a strong attraction between protons and electrons.

-Particles with opposite charges attract one another. E.g.: opposite poles of a magnet.

-Definitions:

Atom: an atom is the smallest unit in an element that can exist by itself.

Molecule: a molecule is 2 or more atoms joined together.

Element: Element is made from one type of atoms only.

Compound: A compound is made up from many molecules joined together.

Attractions between ions:

-The attraction of the ions forms new compounds.

-More electrons than electrons is negative.

-More protons than electrons is positive.

-The electrons and protons keep the compound together.

-The chemical bond is called Ionic bond.

-The difference in charge keeps them together.

-A compound stays together because they share electrons and protons from each other.

Structure of an Atom:

The atoms of all matter are electrical and are made up of three small subatomic particles:

  • Electrons: which carry positive charges.
  • Protons: which carry positive charges.
  • Neutrons: which carry no charge.

Protons and neutrons make up the very dense nucleus of the atom and the tiny electrons are arranged in shells of different energy levels and orbit around the nucleus.

The maximum number of electrons in the first shell is always two, the second is eight and the third is eight. Electrons fill the inside shells first.

Attractions:

  • Atoms are held together by a strong attraction between the protons and electrons.
  • Particles with opposite charges attract one another, like opposite poles of a magnet.
  • The attractions of the ions form new compounds.
  • More electrons then protons are negative.
  • More neutrons than electrons is positive.
  • The protons and electrons keeps the compound together.

Life cycle of a star

-Sun is the nearest star to earth.

-The sun is a bright yellow dwarf star”

  • Sun is about 4.6 billion years.
  • The sun belongs to a galaxy called Milky Way.
  • Only 8.5 light-minutes away from Earth.
  • Sun contains 98% of all the mass of the solar system.
  • It is composed of Hydrogen and a smaller amount of helium.
  • Inside the sun, hundreds of huge nuclear explosions occur each second.

-Stars can’t be seen during the day because the sun blinds us from seeing them.

-Distance in space is measured in light years.

-Galaxies are a huge collection of stars.

Globular clusters:

  • Globular clusters are small and very old stars packed together, they are found outside galaxies.
  • Omega Centauri is a name of a globular cluster.

Inside the stars:

  • The atomic reaction in a star occurs in the core.
  • It takes over 100 000 years for the light and heat produced by the atomic reaction to reach the surface of the star.
  • The energy leaves a star in the form of heat light. ULTRA VIOLET.

Types of stars:

  • The outer planet of our solar system are made of gas same as the stars.
  • There are 4 types of stars:

1-Red Dwarf ( Smallest star 0.2 solar mass)

2-Yellow Dwarf ( solar mass)

3-White Dwarf ( 10 solar mass)

4-Blue dwarf ( 40 solar mass) Largest star

  • The temperature of the star depends on the size of it.
  • The size of a star determines its fate, which means the bigger the star, the longer its life will be.
  • The smaller the star, the shorter the life.

Big Bang:

  • The big bang occurred around 15 billion years ago, there was a giant explosion in space.
  • During the BIG BANG:

1-Everything was compressed to about the size of an atom

2-There was a huge explosion that produced quantities of hydrogen, helium & small amount of lithium.

  • The spiral arms of galaxies grow by collecting gas from space, they form clouds then stars are born there.

- Stars are born in Stella nurseries in the clouds of gases.

How is a star born?

1-Gases fall into the centre of a cloud

2-A protostar is formed but it is not yet hot.

3-Gases spin to form a rotating disc. Planets form in this disc.

4-The protostar in the middle of the disc collects more hydrogen.

5-The squeezing air together (compression) of gases causes the gases in the protostar to heat up.

6-When the temperature is hot enough the hydrogen gas is squeezed together to form an atomic fusion reaction.

7-A star is born.

Features of universe:

  • Galaxy:

- Collection of billions of stars and matter held together by gravity.

- Galaxies are spread over thousands of light years.

- The Milky Way which the sun belongs to is an example of a galaxy.

  • Nebula:

- Is a contracting, swirling cloud of dust, ice and gas that forms a concentric series of rings from which the planets were formed.

  • Black hole:

- A region containing a huge amount of compacted mass.

- It makes its pull of gravity so strong that nothing, not even light, can escape from it.

  • Neutron stars:

- Dense objects

- They form after a supernova occurs.

  • Pulsars:

- Special types of neutron stars that emit beams of radio waves, and also spin.

  • Nuclear fusion occurs when hydrogen nuclei fuse together and release energy.

Hydrogen (Nuclear fusion)  Helium + Energy.

Electromagnetic waves:

- There are two types of waves:

  • Electromagnetic waves and
  • Mechanical waves.

- Electromagnetic waves are composed of electric and magnetic fields and do not need particles to transfer energy, that is, they can travel through a vacuum. The electromagnetic spectrum contains several types of electromagnetic waves:

Radio Waves: / Transmit radio and TV Signals, radar in air traffic control
Microwaves: / Cooking, radar speed guns used by police
Infrared waves: / Given off by hot objects, used to take temperature pictures and find people in collapsed buildings.
Visible Light: / Seeing, photosynthesis, photography
UV Rays / Fluorescent lamps, sterilising
X Rays / Radiography, treating cancer, finding faults in metals, examining crystals.
Gamma Rays / Measure thickness of metals, sterilise medical equipment.

- Electromagnetic waves travel through space at the speed of light.

- There are 2 types of Electromagnetic waves:

  • Transverse waves and
  • Longitudinal waves.

- Transverse waves: in transverse waves the particles vibrate at right angles to the direction of the wave. I.e.: Vibrates Up and down. The wavelength of a transverse wave is the distance from one crest to the next.

- Longitudinal waves do not look wavy; they can be seen as a pulse along a stretched spring. The wavelength of a longitudinal wave is the distance between two compressions.

Wave Sample:

Note: As the wave transmits energy, the trough becomes the crest and the crest becomes the trough because the wave is moving up and down.

Parts of wave:

- Crest: Crest is the top part of a wave.

-Trough: The trough is the bottom part of a wave.

-Wave Length: Wave length is the distance between each group.

-Amplitude: is the distance from the imaginary line to the crest or the imaginary line to the trough.

-Frequency: the number of waves produced per second, measured in Hertz (Hz)

-Wave Speed (m/s) = Frequency (Hz) x wavelength (m)

Electromagnetic Waves:

  • All waves transfer energy without moving material in the direction that they are moving. They may be vibrations that go up and down, or back and forth.
  • The lower the frequency in a wave, the longer the wave length.
  • The higher the frequency, the shorter the wave length.

Lights:

- An object that lights is called a Luminous Object, eg: Sun, switched on light bulbs, and burning wood.

- An object that light shines upon is called an illuminated object, eg: the moon, in fact most things are illuminated.

- A small luminous body is called a point source.

- A light that spreads out greatly is called an extended light source.

- Light travels in a straight line, it moves along 300 000 km/s, light doesn’t ned any medium in order to travel.

- When light strikes matter, 3 things happen, it can be: absorbed, reflected or transmitted.

  1. When light is absorbed, it’s taken in by the matter it strikes. Substances like wood and metal do not transmit light they only absorb, we can’t see through them at all. They are called opaque.
  2. When light is reflected, it bounces off the substance it strikes. A mirror is a common example. Light that is transmitted passes through the matter it strikes. Transparent substances transmit light eg: window glass, water and air.
  3. Substances that scatter the light are called TRANSLUCENT, because we can see the light through them but we cannot see any details, eg: waxed paper and frosted glass.

Reflection:

  • Angle of reflection is the angle between the normal and the reflected ray.
  • Angle of incidence is the angle between the normal and the incident ray.
  • Angle of incidence and angle of reflection are always equal.
  • The normal is an imaginary line between the angle of reflection and angle of incidence; it bisects the angle in half.

Refraction:

  • Refraction is the bending of light as it passes from one medium to another.
  • When light passes through a glass slab, the light is transmitted and bent.
  • This bending of light is called refraction.
  • Air is less dense than glass.
  • Light bent when the medium changed.
  • Refraction occurs when light passes from one medium to another,
  • When light travels from a less dense medium to a denser medium the lights travel towards the normal.
  • When light travels from a denser medium to a less dense medium the lights travels away from the normal.
  • Always Speed depends on density.
  • Different substances have different densities. For example water is denser than air.

Laws of Refraction:

  1. Light that moves at an angle from a ales dense medium to a more dense medium bends towards the normal.
  2. Light that moves straight on from one medium to another does not bend. It is not refracted.
  3. Light that moves at an angle from a denser medium to a less dense medium bends away from the normal.

Reproduction:

Reproduction is a life function, it means creating new life.

Asexual Reproduction:

Asexual reproduction occurs when there is only on parent. It occurs in less complex organisms such as unicellular organisms.

Sexual Reproduction:

Sexual reproduction involves 2 parents, a male and female. It occurs in more complex living organisms.

Mitosis:

Mitosis is the type of cell division that leads to the growth and development of an organism. Mitosis occurs in all cells except for sex cells. Human cells have 46 chromosomes’.

Types of Cells Mitosis Produces:

-Cells needed to make an adult organism from a fertilised egg.

-Cells needed to heal cuts, wounds and broken bones

-Cells that replace dead skin cells.

Process of Mitosis

-Step One:

  • Cell becomes larger
  • Chromosomes become visible

-Step Two:

  • Chromosomes double by splitting into two and pair up

-Step Three:

  • Double chromosomes line up across the equator of the cell
  • Membrane of nucleus disappears

-Step Four:

  • Doubles separate
  • Chromosomes move on the spindle form to go to opposite poles (ends) of the cell

-Step Five:

  • Membrane divides the cell into two
  • Each new cell have the same number of chromosomes as the original

-Step Six:

  • Chromosomes form nucleuses of the new cells

Meiosis:

Meiosis is the divion of cells to create sex cells. Sex cells only have 23 chromosomes.

Process of Meiosis

-Step One:

  • Cell becomes larger
  • Chromosomes become visible

-Step Two:

  • Chromosomes double by splitting into two and pair up

-Step Three:

  • Membrane divides the cell into four
  • Each new sex cell has half the number of chromosomes as the original

-Step Four:

  • Chromosomes form nucleuses of the new cells

Genetics

Genetics refers to the study of hereditary and inherited characteristics.

Chromosomes

-Long thin threads

-Contains chemicals which control what the cell does

-Human cells have 46 chromosomes except for sex cells which have 23 chromosomes

-Chromosomes hold DNA as a compact coil…

DNA

-Deoxyribonucleic Acid

-Stores the coded information that determines human characteristics

-DNA consists of nucleotides…

Nucleotides

-Building blocks of DNA arranged to form a genetic language or code

-Four different nitrogenous bases

  • Adenine (A)
  • Thymine (T)
  • Cytosine (C)
  • Guanine (G)

-Base Pairing Rule > A is chemically attracted to T

> C is chemically attracted to G

-Nucleotides make up genes…

Genes

-Sections of DNA which contain complete messages or sets or particular instructions

-Locus > the position occupied by the gene on the chromosome

-Genome > Same set of genes in each cell of an organism

-The message in the gene is the coded formula needed to produce protein…

Protein

-Instructions in the gene code for the production of protein which are essential to the cell

-The life processes inside your body are carried out by a group of proteins called enzymes

-Before the instruction can be carried out it must be copied so that the master plan remains in the cell

RNA

-Copy of the DNA sequence

-Passes through the pores of the nuclear membrane into the cytoplasm to the ribosomes where proteins are manufactured

-Code for the production of the protein is carried in messenger RNA

Genotype : Genotype is a person’s genetic coding.

Phenotype : Phenotype is how living things appear and function. This is caused by the combined effect of their genotype and their environment.

DNA Mutation:

  • Mutations are the continual source of variation on which natural selection can act.
  • Cancers are due to a genetic change in a single cell.
  • Mutations that occur in body cells are known as somatic mutations.
  • Mutations are a source of new alleles in an organism.

Types of Mutations:

  • Aneuploidy: When an individual has an abnormal chromosome number.
  • Polyploidy: When an individual has one or more extra sets of chromosomes.

Changes in DNA sequence:

  • Most mutations involve changes in the DNA sequence.
  • Large changes may alter the structure of chromosomes and be visible when looking at chromosomes under the microscope.
  • When groups no longer share a pool of common genes, they are likely to become separate species over time.

DNA Structure