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Year 9 Science

Exam Revision

Semester 2

CHEMICAL

REACTIONS

The Atom

Negatively

charged electrons

Positively charged

protons

Neutrons

NUCLEUS

Electron shell

The Atom

• An atom has a neutral charge: number of protons = number of electrons

• 2 electrons can fit in the first shell of an atom & 8 in each subsequent shell

• Atomic number (Z) = number of protons in an atom’s nucleus

• Mass number (A) = number of protons + number of neutrons

• Number of neutrons in an atom = mass number minus atomic number

The Periodic Table

• Table created to group elements according to

their properties

• Vertical columns = groups

• Horizontal rows = periods

• Group number = number of electrons in outer

shell

• Period number = number of shells

The Periodic Table

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The Periodic Table The Periodic Table

Chemical & Physical Change

CHEMICAL CHANGE PHYSICAL CHANGE

Produces a new substance No new substances

produced

Cannot be easily reversed Can be easily reversed

Clues that a chemical reaction took

place: light, change in temperature,

colour change, gas production,

smell

Involves a change in state or

change in shape

Occurs when bonds between atoms

break and new ones are formed

Caused by motion,

temperature & pressure

E.g. cooking an egg, rusting of an

iron pan, burning wood

E.g. crushing a can, melting

an ice cube, boiling water

Chemical OR Physical?

• Burning paper

• Baking a cake

• Sweat cools you as it evaporates

• Boiling water added to instant coffee

• Photosynthesis

• Margarine is melted

CHEMICAL

CHEMICAL

PHYSICAL

CHEMICAL

PHYSICAL

PHYSICAL

Chemical Reactions

• Occur when bonds between atoms break and

new ones are formed

• Reactants � Products

Conservation of Mass

• Matter cannot be created or destroyed

• Law of Conservation of Mass: mass of the reactants is equal to the mass of the products

• i.e. all atoms present at the beginning of the reaction are present at the end of the reaction (and in the same proportion)

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Endothermic & Exothermic Reactions

ENDOTHERMIC EXOTHERMIC

Absorb energy from

surroundings

Release energy

More energy at end of

reaction than at end

More energy at start of

reaction than at end

E.g. instant ice packs,

photosynthesis

E.g. portable hand

warmers, airbags, dynamite

Acids & Bases: Characteristics

ACIDS BASES

Corrosive Can be corrosive

Sour taste Bitter taste

Slippery or soapy to touch

Acids or Bases? Acid-Base Indicators

• Added to a substance to determine if it is an

acid or a base

• Litmus:

– Turns RED in an acid and BLUE in a base

• Bromothymol blue:

– Turns YELLOW in an acid and BLUISH-

PURPLE in a base

The pH Scale

• Shows the relative strength of an acid or a

base

• pH of a substance can be determined using a

universal indicator

• Is a mixture of indicators that will change

colour based on the strength of the acid or the

base

The pH Scale

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Neutralisation

• Acid + base � water + a salt

– Sometimes a gas is also a product

• Stop the effects of an acid by adding a base

• Stop the effects of a base by adding an acid

• Examples:

– Relieve an ant sting by adding a weak base (e.g.

sodium bicarbonate – baking soda)

– Relieve a wasp sting by adding a weak acid (e.g.

vinegar)

Types of Chemical Reactions:

Combustion

• Combustion reaction: a substance (called a

fuel) reacts with oxygen and heat is produced

• Fuel + oxygen � carbon dioxide + water

• Examples of fuels: natural gas, petrol, coal

• Combustion can also produce dangerous

gases (e.g. carbon monoxide)

Combustion Examples

• Gas stoves– Natural gas (methane) + oxygen �

carbon dioxide + water

• Cars– Fuel (octane) + oxygen � carbon dioxide

+ water

• Aeroplanes– Fuel (kerosene) + oxygen � carbon

dioxide + water

• Electricity– Coal + oxygen � carbon dioxide + water

Types of Chemical Reactions: Respiration

• Occurs in every cell in your body

• Is how cells produce energy

• Is a type of combustion reaction

• Glucose + oxygen � carbon dioxide + water

THE BODY AT WARIntroduction to Diseases

• Disease: any change that impairs the function of an individual in some way (causes harm).

• Non-infectious diseases: cannot be spread from one person to another (e.g. obesity, cancer, haemophilia, cystic fibrosis)

• Infectious diseases: contagious, can be spread from one person to another, are caused by a pathogen (e.g. influenza, common cold, HIV)

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How can disease be spread?

• Direct contact: touching others, sharing body

fluids, airborne droplets from coughing/

sneezing may contain pathogens that land on

other people or objects.

• E.g. common cold.

How can disease be spread?

• Vectors: organisms that carry a

disease-causing pathogen

without being affected by the

disease (e.g. mosquito,

houseflies, rats, mice)

• E.g. mosquito carries malaria

How can disease be spread?

• Contaminated objects: an infected person may

touch an object (e.g. towel, handrail, surface)

leaving infected skin cells. Another person who

touches the object may become infected.

• E.g. food poisoning caused by contamination of

food by hands.

How can disease be spread?

• Contaminated water: pathogenic organisms

live in water and it must be treated before

drinking.

• E.g. E.Coli

How can spread of disease be prevented?

• Quarantine: separating sick

people from others that could be

infected.

• Personal hygiene & care with

food: washing hands properly,

ensuring food is properly cooked

How can spread of disease be prevented?

• Proper waste disposal

• Public Education

• Chemical control of vectors

• Chemical treatment of clothes, surfaces, water

• Pasteurisation of milk

• Drugs such as antibiotics

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Outbreak of Disease

• Plague: contagious disease that has spread rapidly through a population and resulted in high death rates.

• E.g. Bubonic plague: caused black sores on the

skin of victims. Caused by a bacteria. Rats carried

the bacteria, fleas that bit an infected rat carried

the bacteria (flea was the vector) and humans

were infected when bitten by a flea. Caused

widespread death in Europe in the 1300s.

Outbreak of Disease

Cases of disease A

Cases of disease B

Which is an epidemic &

which is a pandemic?

Outbreak of Disease

• Pandemic: diseases that occur worldwide.

• Epidemic: occur when many people in a

particular area have the disease in a relatively

short time.

Pathogens

• A disease-causing agent

• E.g. bacteria, virus, fungi, prion, protozoa, some

animals

Parasites

• An organism that lives in or on a host

• Obtains benefits such as nutrition & a place to

live

• May harm the host

• Endoparasites: live in their host (e.g. tapeworm)

• Ectoparasites: live on the host (e.g. lice)

Prions

• Non-cellular

• Abnormal proteins that are infectious

• Cells containing prions burst

• This releases the prions to infect other cells

• Prions then turn normal proteins into prions

• Cause neurological problems such as ‘mad cow

disease’

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Viruses

• Non-cellular

• Consist of DNA wrapped in protein

• Can only be seen under the microscope

• Cannot reproduce on their own – use a host cell

• Release their DNA into the host cell

• Host cell then copies the DNA of the virus

• Host cell bursts, releasing more viruses

Bacteria

• Single-celled

• Reproduce via binary fission

• Can be responsible for a variety of different diseases

• E.g. tetanus, pneumonia, food poisoning

Protozoa

• Single celled

• Common in tropical areas

• Various different types

• Malaria and African Sleeping Sickness are caused by protozoans

Fungi

• May be large (e.g. toadstools) or microscopic

(e.g. moulds growing on bread)

• E.g. tinea, thrush, ringworm

Worms & Arthropods

• E.g. tapeworms

• Live in the intestine

• Have hooks & suckers to keep hold

• Other examples: lice, fleas, ticks

Lines of Defence

• When a foreign organism invades our body, we

must use defence systems to fight off disease

• This is called the immune response

• The immune response involves three lines of

defence

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First Line of Defence

• Purpose is to prevent of pathogens into the

body. May be physical barriers

• May be physical barriers (e.g. the skin, coughing,

sneezing, nasal hairs, cilia) OR

• Chemical barriers (e.g. body fluids like saliva,

tears, stomach acid)

Second Line of Defence

• Involves white blood cells called phagocytes

• Phagocytes engulf and destroy the pathogens

• Is the reason for the redness / swelling (inflammation) / increase in temperature that occurs when you have an infected cut – more blood being sent to this area with WBCs to destroy the pathogens

Third Line of Defence• Involves the lymphatic system and lymphocytes

(type of white blood cell)

• Any foreign cells have antigens (markers on the

outside of the cell that allow the body to

recognise foreign particles

• B lymphocytes produce antibodies

• Each antibody matches a specific antigen & will

help to destroy cells with this antigen

• T lymphocytes destroy foreign invading cells &

infected body cells, reducing the chance of the

pathogen spreading to other cells

Immunity

• Immunity: resistance to a particular pathogen or disease

• Once the body has been exposed to a particular antigen, they make antibodies against it.

• The next time you exposed to this antigen, your body ‘remembers’ how to fight the particular pathogen.

• Your immune response to this pathogen is faster and more effective because you have been exposed to it before

• Your body is able to resist infection

• Vaccination: injection with dead or weakened form of a pathogen. Can provide immunity to a disease.

Types of Immunity

• Active immunity: your body produces antibodies to a specific antigen. Your body then has memory cells that remember the antigen and can make antibodies again quickly if you were infected again.

– Natural: antibodies made after body is exposed to antigen.

– Artificial: antibodies made after vaccination.

• Passive immunity: receiving antibodies from an outside source. Does not result in memory cells for the infection so if you were exposed to the disease again your immune response would be exactly the same.

– Natural: antibodies pass to baby across placenta or through mother’s milk.

– Artificial: antibodies are injected into the body.

Malaria

• Caused by a protozoa (Plasmodium)

• Can contract malaria if you are bitten by a female mosquito that has been infected with the Plasmodium parasite

• Parasite moves into the salivary glands of the mosquito and passes into your bloodstream when bitten

• Symptoms: fever, aches & pains, shivering, night sweats, fatigue, low blood cell counts, jaundice

• Can have severe complications such as cerebral malaria, anaemia and death

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Malaria

• Once malaria is in your body the parasites grow and

multiply in your liver cells and then in your red blood

cells (RBCs)

• The continue growing in your RBCs until the RBCs burst

• The new malaria parasites infect new cells in the body

ECOSYSTEMS

Ecology: The study of organisms and

how they interact with each other

and their environment.

Introduction to Ecosystems

• Species: Organisms that

can reproduce with each

other and produce fertile

offspring (offspring that

are also able to

reproduce) are members

of the same species.

• Population: A group of

organisms of the same

species living in the same

area at the same time.

Introduction to Ecosystems

• Community: Two or more populations of organisms living in the same area and the same time.

• Ecosystem: A community of organisms living together and interacting with each other and their environment, including non-living (abiotic) factors.

Introduction to Ecosystems

• Producer/autotroph: make own food via photosynthesis.

Convert inorganic compounds (water and carbon dioxide)

into organic materials (glucose)

• Consumer/heterotroph: obtain nutrition by eating other

organisms

– Herbivore: eat plants

– Carnivore: eat other animals

– Omnivore: eat both plants & animals

– Detritivore: feed on organic matter in rotting leaves, dung,

decaying animal remains

– Decomposer: convert organic matter into inorganic matter.

Inorganic material enters soil & is reused by producers.

Interactions Between Species

• Within an ecosystem, organisms occupy a

niche

• The niche of a species includes:

– its habitat (the place where it lives)

– nutrition (how it obtains its food)

– relationships (interactions with other species in

the ecosystem)

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Interactions Between Species

• Competition: organisms compete with each other for resources such as food, shelter or mates

• Interspecific competition:competition between members of different species

• Intraspecific competition:competition between members of the same species

Interactions Between Species

• Predator-prey relationship: one species kills and eats another species. Predator is the killer/eater & prey is the food source

– e.g. eagles/rabbits, spiders/flies, snakes/mice

• Herbivore-plant relationship:herbivore eats a plant. Plants defend with thorns, spines, stinging hairs, chemicals that are distasteful, dangerous or poisonous

Types of Symbiotic Relationships

• Symbiotic relationship:an interaction between species where at least one species benefits

• Parasitism: one organism lives in or on its host, gaining benefits (e.g. food, shelter) while harming the host

Types of Symbiotic Relationships

• Mutualism: both species benefit from the interaction

• Commensalism: one species benefits from the interaction while the other species does not benefit and is not harmed (i.e. no effect on the second species)

Biotic and Abiotic Factors

• Biotic factors: living things in an ecosystem

– E.g. other organisms of the same species,

predators, prey, plants

• Abiotic factors: non-living things in an

ecosystem

– E.g. water, pH levels, temperature, light levels

Biotic and Abiotic Factors

• Tolerance range: the range of a particular abiotic factor within which an organism can survive

• Optimum range: range within the tolerance range in which an organism functions best

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Sampling Ecosystems

• Sampling methods used to determine the following information:

– Population Density: how many organisms live in a particular area (e.g. number of gum trees per square km)

– Population Distribution: the geographical area in which that species can be found

– Population size: how many organisms live in that population

Sampling Ecosystems:

Quadrats

• Squares

• Placed in a particular area & the number of individuals

of a species in each quadrat are counted

• Can use the results from several quadrats to estimate

population size

• Organisms should be slow moving or stationary

Sampling Ecosystems: Mark-

Recapture Technique

• Used when animal populations are very mobile

STEP 1

• Collect a sample of the animal population being

studied (e.g. with nets, traps)

• Mark the animals (e.g. leg bands, tiny spots of

paint, trackers)

• Release them

Sampling Ecosystems: Mark-

Recapture Technique

STEP 2

• Collect another sample of the population & note down how many tagged/untagged individuals there are

• Estimate the total population size using the following formula

Size of population (N) = total number of animals marked and released (first sample; M) x total number of recaptured animals (second sample; C) ÷ number of

animals in second sample that are marked (R)

• N = M x C / R

Food Chains and Food

Webs

Producer/1st trophic level 1st order consumer/2nd trophic level

2nd order consumer/3rd trophic level

Top carnivorePlant Structure and Function

• Roots: anchor plants into soil, hold soil in

place & prevent erosion, absorb water &

nutrients for the plant

• Root hairs: tiny hairs on roots that increase

the amount of surface area available for

absorption

• Stems: support the plant, keep it upright,

carry nutrients throughout the plant, contain

xylem and phloem for transport

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Plant Structure and Function

• Xylem: thick tubes that assist in supporting

the plant, transport water from roots to leaves

(transpiration stream)

• Phloem: transports organic substances such as

sugars throughout the plant (translocation)

Plant Structure and Function

Plant Structure and Function

• Leaves: trap sunlight so plants can perform

photosythesis, allow plant to take in carbon

dioxide and release oxygen

• Chloroplasts: structures found in leaf cells

that contain a chemical called chlorophyll.

• Chlorophyll: absorbs light energy from the sun

to be used for photosynthesis

Photosynthesis

• Used by producers to make their own food

• Carbon dixoide enters plant via leaves

• Water travels from roots to leaves

• Sunlight energy absorbed by chlorophyll

• Glucose used by the plant for energy (to

perform cellular respiration)

• Oxygen released from leaves into atmosphere

Leaf Structure and Photosynthesis

• Leaves have openings called stomata: small pores on surface of leaves

Leaf Structure and Photosynthesis

• Stomata allow carbon dioxide and oxygen enter and leave the plant

• The can open or close based on the plants needs: will close to prevent water loss but cannot remain closed as the plant can’t take in carbon dioxide and release oxygen

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Leaf Structure and Photosynthesis

• When plant has lots of water, water moves into guard cells, making them turgid

• This opens the stoma

• If the plant does not have enough water, guard cells lose water and become flaccid

• This closes the stoma as the guard cells collapse into each other

Cellular Respiration

• Carried out by all living things in order to

produce energy

• Energy is used to: move, grow, reproduce….

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