Exam Notes

Motion

• Motion or movement happens around us every day.

• Examples of motion:

  • A DVD spins in a circular manner.

  • A guitar string vibrates when plucked.

  • A car or train moves in linear motion.

Objects Moving in a Straight Line

• This chapter focuses on objects moving in a straight line.

• Terms to describe motion:

  • Speed

  • Velocity

  • Acceleration

• Importance of using SI units.

Speed

• Speed is related to the distance traveled and the time it takes to travel that distance.

Units for Speed

• Distance should always be converted to meters (m).

  • $100 \text{ cm} = 1 \text{ m}$

  • $70 \text{ cm} = 0.7 \text{ m}$

  • $16 \text{ cm} = 0.16 \text{ m}$

  • $1 \text{ km} = 1000 \text{ m}$

  • $4 \text{ km} = 4000 \text{ m}$

  • $7.5 \text{ km} = 7500 \text{ m}$

• Time should always be converted to seconds (s).

  • $1 \text{ minute} = 60 \text{ s}$

  • $5 \text{ minutes} = 60 \times 5 = 300 \text{ s}$

  • $1 \text{ hour} = 60 \times 60 = 3600 \text{ s}$

Calculating Speed

• Triangle method:

  • D = distance

  • S = speed

  • T = time

• To calculate distance: $\text{distance} = \text{speed} \times \text{time}$

• To calculate speed: $\text{speed} = \frac{\text{distance}}{\text{time}}$

• To calculate time: $\text{time} = \frac{\text{distance}}{\text{speed}}$

Speed Sample Calculations

• Calculation 1: A car travels 400 m in 10 s.

  • Answer: $\text{speed} = \frac{400 \text{ m}}{10 \text{ s}} = 40 \text{ ms}^{-1}$

• Calculation 2: A train travels 1.8 km in 1 minute.

  • Answer: $\text{speed} = \frac{1800 \text{ m}}{60 \text{ s}} = 30 \text{ ms}^{-1}$

• Calculation 3: How long does it take a car traveling at $40 \text{ ms}^{-1}$ to travel 720 m?

  • Answer: $\text{time} = \frac{720 \text{ m}}{40 \text{ ms}^{-1}} = 18 \text{ s}$

• Calculation 4: Calculate the distance traveled by a person running at $5 \text{ ms}^{-1}$ for 2 hours.

  • Answer: $\text{distance} = 5 \times 2 \times 60 \times 60 = 36000 \text{ m}$

Calculating Speed with Graphs

• The slope of a distance-time graph represents speed.

• A steeper slope indicates a larger value of speed.

• A horizontal line on a distance-time graph indicates the jogger is not moving.

• A negative slope indicates the jogger is returning to the starting point.

Velocity

• Velocity includes both speed and direction.

• Direction is given using points of the compass (north, south, east, west).

• Unit for velocity is the same as speed: $\text{m/s} \text{ or } \text{ms}^{-1}$

• Skydivers reach a 'terminal velocity' after falling for a short time.

Acceleration

• Acceleration is the rate of change in velocity (can be an increase or decrease).

• Deceleration is negative acceleration.

• Formula for acceleration: $\text{acceleration} = \frac{\text{change in velocity}}{\text{time}}$

• Unit for acceleration: $\text{ms}^{-1} \text{ divided by the second} = \text{m/s}^2 \text{ or } \text{ms}^{-2}$

Acceleration Sample Calculations

• Calculation 6: A car's speed changes from $4 \text{ ms}^{-1}$ to $28 \text{ ms}^{-1}$ in 12 s.

  • Answer: $\text{acceleration} = \frac{28 - 4}{12} = 2 \text{ ms}^{-2}$

• Calculation 7: A train starts from rest and reaches a speed of $90 \text{ ms}^{-1}$ in 2 minutes.

  • Answer: $\text{acceleration} = \frac{90 - 0}{2 \times 60} = 0.75 \text{ ms}^{-2}$

• Calculation 8: A car's speed changes from $50 \text{ ms}^{-1}$ to $8 \text{ ms}^{-1}$ in 14 seconds.

  • Answer: $\text{acceleration} = \frac{8 - 50}{14} = -3 \text{ ms}^{-2}$

  • This is a deceleration.

The Sun, Earth, and Moon

• The Sun is a star.

• Earth is a planet.

• The Moon is a satellite of Earth.

• Their relationship is based on their positions relative to one another.

Lunar Cycle

• Lunar cycle refers to the changes in the appearance of the Moon.

• Luna is the Latin term for the Moon.

• Changes in the Moon’s appearance from night to night are called the phases of the Moon.

• Each phase relates to the Moon's position relative to Earth and how much sunlight is reflected.

Phases of the Moon

• Phase 1: New Moon

  • Earth, Sun, and Moon are approximately in a straight line, with the Moon between Earth and the Sun.

  • The Moon is not visible from Earth.

• Phase 2: Waxing Crescent

  • Waxing means ‘growing’.

  • Increasing levels of sunlight are reflected.

  • Less than half of the Moon is visible.

• Phase 3: First Quarter Moon

  • On day 7, exactly half of one side of the Moon is visible.

• Phase 4: Waxing Gibbous

  • More of the Moon becomes visible.

  • Gibbous refers to a moon between a half-moon and a full moon.

• Phase 5: Full Moon

  • On day 14, Earth, Sun, and Moon are approximately in a line, with Earth in the middle.

  • The side of the Moon facing Earth is fully sunlit.

• Phase 6: Waning Gibbous

  • Waning means ‘shrinking’ or ‘getting smaller’.

  • A complete moon is no longer visible due to decreased sunlight.

• Phase 7: Third Quarter

  • On day 21, half of the illuminated side of the Moon is visible.

• Phase 8: Waning Crescent

  • Only part of the Moon (a crescent) is visible.

  • Occurs just before another new moon.

Seasons

• Seasons are linked to the movement of Earth around the Sun.

• Seasons cause changes in weather, temperature, and daylight hours.

• Earth is closest to the Sun during winter and farthest away during summer.

• Earth rotates on a tilted axis of 23.5°.

• The part of Earth tilted towards the Sun experiences summer, while the part tilted away experiences winter.

Angle of Sun's Rays

• Larger angle (e.g., 90°): more direct heat energy, warmer temperatures (summer).

• Smaller angle (e.g., 26°): less direct heat energy, cooler temperatures (winter).

Eclipses

• An eclipse occurs when one celestial body blocks the light from another.

• Types of eclipses: lunar and solar.

Lunar Eclipse

• Earth passes between the Sun and the Moon, blocking the Sun’s light from reaching the Moon.

Solar Eclipse

• The Moon passes between the Sun and Earth, casting the Moon’s shadow on parts of Earth.

Shadows During Eclipses

• Umbra: the dark shadow where light is completely blocked.

• Totality: when the umbra completely covers another body.

• Penumbra: a partial or less darkened shadow seen at the first and final stages of an eclipse.

Chemical Reactions

Rate of Reaction

• The rate of a chemical reaction tells us how quickly it happens.

• Slow reaction: Rusting of iron.

• Fast reaction: Explosion.

• In industry, it's crucial to know how long a reaction will take.

• Chemists measure how many reactants are used up and how much product is formed in a certain time.

• Rate = Amount of reactants used up or product formed / Time

Particle Theory

• During a chemical reaction, reactant particles are always moving.

• Reaction rate depends on how often and how hard reacting particles collide.

• Particles must collide with enough energy to break bonds in molecules.

• Increasing the rate of reaction involves increasing the number of successful collisions.

Factors Affecting Reaction Rate

• Stirring the solution: Increases collisions and reaction rate.

• Increasing temperature: Particles have more energy, move faster, increasing collisions and reaction rate.

• Increasing surface area: Smaller particle size increases surface area, which increases the reaction rate.

• Increasing concentration: Increases the number of particles, resulting in more collisions and a faster reaction rate.

• Catalyst: Alters the rate of a reaction without being used up.

Surface Area and Reaction Rate

• The steepest part of the curve is at the start (fastest part), but the curve becomes less steep as the reaction slows down.

• The curve becomes flat, indicating the end of the reaction.

Concentration and Reaction Rate

• Reaction is fastest at the start (steep curve), gradually becoming slower as the reaction proceeds.

• The curve goes flat when the reaction is complete.

Catalysts

• Transition metals (between Group 2 and Group 3) and their compounds are important catalysts (e.g., iron, copper, chromium, nickel, gold).

• Catalysts lower the activation energy, making it easier for particles to react, increasing the rate of reaction.

• Activation energy is the minimum energy needed for reactant particles to react.

Biochemical Reactions

• Factors affecting respiration, photosynthesis, etc.

• Photosynthesis is affected by light intensity, carbon dioxide, and temperature.

Energy Changes in Chemical Reactions

Temperature Change

• Changes in temperature can indicate that a chemical reaction has taken place.

• Heat energy is usually released or taken from the surroundings.

Exothermic Reactions

• Energy is transferred from the chemicals to the surroundings.

• The temperature of the reaction mixture rises.

• Example: Combustion (burning fuels or fireworks).

Endothermic Reactions

• Energy is absorbed by the chemicals from the surroundings.

• The reaction mixture shows a fall in temperature.

• Example: Ammonium chloride dissolving in water.

Heat Transfer

• Exothermic: Heat 'exits' (is given out), temperature outside goes up.

• Endothermic: Heat 'enters' (is taken in), temperature outside goes down.

Bonds and Energy

• During a chemical reaction, old bonds are broken (reactants) and new bonds are formed (products).

• Breaking bonds requires energy (endothermic).

• Energy is released when new bonds are formed (exothermic).

Bond Energy

• Bond energy: Energy required to break different bonds.

• Units: kilojoules per mole (kJ/mol).

• A mole (symbol ‘mol’) is the unit used to measure the amount of a substance.

• Examples of bond energies:

  • H―H: $436 \text{ kJ/mol}$

  • Cl―Cl: $242 \text{ kJ/mol}$

  • H―Cl: $431 \text{ kJ/mol}$

  • C―H: $413 \text{ kJ/mol}$

  • C―C: $347 \text{ kJ/mol}$

  • C―O: $335 \text{ kJ/mol}$

Energy Profile Diagrams

• Show the energy transfer in reactions.

• Show the energy stored in reactants vs. products to determine if a reaction is exothermic or endothermic.

• Activation energy is the minimum energy that colliding particles must have for a reaction to occur.

Exothermic Reaction Diagram

• Products are at a lower energy than reactants, so energy has been given out.

• $\Delta H$ (change in energy) is negative.

• The difference in energy is given out as heat, so the temperature of the surroundings rises.

Endothermic Reaction Diagram

• Products are at a higher energy than reactants.

• Extra energy was required to form the products, which was taken in from the surroundings; the temperature of the surroundings falls.

• $\Delta H$ (change in energy) is positive.

Energy Transfer

• Energy transfer is not always heat.

• Photosynthesis requires light energy, not heat energy.

• Photosynthesis converts light energy from the Sun to chemical energy (glucose).

Atoms, Elements, Molecules, and Compounds

Atoms

• Atoms are the basic building blocks of all materials.

• The word ‘atom’ comes from a Greek word meaning something that cannot be divided.

Element

• An element is a substance made up of only one type of atom.

• Carbon is an element because it contains only carbon atoms and cannot be broken down.

Periodic Table

• The periodic table shows a list of all the elements.

Symbol

• Each element has a symbol.

  • Hydrogen: H

  • Iron: Fe (from Latin ferrum)

  • Oxygen: O

  • Carbon: C

  • Potassium: K

  • Nitrogen: N

Molecules

• A molecule is formed when two or more atoms join (bond) together chemically.

Compounds

• A compound is a molecule made up of two or more different types of elements chemically combined.

• All compounds are molecules, but not all molecules are compounds.

• Hydrogen gas (H2) and oxygen gas (O2) are not compounds because each is composed of one element.

• Water (H2O) and carbon dioxide (CO2) are compounds because each is made up of more than one type of element.

• All compounds are non-elements.

Models

• Models show how atoms bond (join) to each other.

Structure of the Atom

• The atom is made up of smaller particles called sub-atomic particles:

  • Protons

  • Neutrons

  • Electrons

Properties of Sub-Atomic Particles

Size of Sub-Atomic Particles

• Electrons are much smaller than protons and neutrons.

• 1840 electrons ≈ 1 proton.

Atomic and Mass Numbers

• Atoms of different elements differ by the number of protons, neutrons, and electrons.

• Atomic number: Number of protons (same as the number of electrons).

• Mass number: Number of protons and neutrons.

Example

• Atomic number: 3 protons, 3 electrons

• Mass number: 7 – 3 = 4 neutrons

Arrangement of Electrons

• Electrons move around the nucleus in energy levels called shells, or orbits.

• First shell: Holds up to 2 electrons.

• Second and third shells: Each holds up to 8 electrons.

• Electrons fill up the shells one by one starting with the first shell.

• Atoms 'like' to have full electron shells.

• If the outer shell is not full, the atom 'wants' to react to fill it.

Bohr Model

• Niels Bohr suggested the idea of electron shells.

• The way electrons are arranged is called the electron configuration.

• The way they are explained is the Bohr model.

  • Examples: Helium, Lithium, Magnesium

Reproduction

Sexual vs. Asexual Reproduction

• Reproduction: Production of new individuals

• Asexual reproduction: Offspring from one parent only

• Sexual reproduction: Offspring from two parents

• Humans reproduce sexually.

Male Reproductive System

Testis

• Makes sperm, starting between 12 and 14 (puberty).

• Sperm created in huge numbers

• Puberty also leads to:

  • Enlargement of the penis and testes.

  • A rapid growth spurt.

  • Enlargement of the voice box (larynx or Adam’s apple), causing the voice to deepen.

  • Growth of hair on the body.

Scrotum

• Sac holding testes outside the body.

• Keeps testes at a temperature just lower than body temperature for successful sperm production.

Sperm Ducts

• Carry sperm from the testes to the penis.

• Glands produce seminal fluid.

• Mixture of sperm and seminal fluid is called semen.

Penis

• Sperm ducts join the urethra.

• Sperm pass through the urethra in the penis.

• Allows semen to pass out of the male body into the female.

Female Reproductive System

Ovary

• Produces eggs, starting at puberty (10-13).

• Puberty in girls also lead to:

  • Growth of the pelvis, breasts, vagina, and uterus.

  • Growth of hair on parts of the body.

• Beyond 35, egg production decreases; stopping between 45 and 55 (menopause).

Fallopian Tube

• Collects egg from the ovary and carries it to the uterus.

• Sperm may join (fuse) with the egg in the fallopian tube.

• Egg dies within 2 days if no sperm is present.

Cervix

• Opening/neck of the uterus.

• Sperm pass through the cervix to reach an egg.

Vagina

• Muscular tube into which the penis releases sperm.

• Forms the birth canal when the baby passes down during childbirth.

Menstrual Cycle

• Series of changes that take place in females about every 28 days between puberty and menopause.

• Does not take place during pregnancy.

• Outline:

  • Days 1-5: Breakdown of the uterus lining, along with blood, passed out of the body (menstruation). A new egg matures in the ovary.

  • Day 14: Egg released from the ovary (ovulation). Egg can survive for 2 days in the fallopian tube.

  • Days 15-28: The lining of the uterus remains in place and breaks down on the first day of the next menstrual cycle.

Fertile Period

• Sperm can survive in the female reproductive system for 5-7 days.

• The egg stays alive for 2 days.

• Fertile period: Time in the menstrual cycle when pregnancy is most likely to take place (day 9 to day 16 of a 28-day cycle).

Sexual Intercourse

• Also called copulation.

• Erect penis of the male is placed in the vagina of the female, causing semen to be released.

Sperm in the Vagina

• Millions of sperm are released into the vagina.

• Sperm move through the cervix and into the uterus, then toward a fallopian tube.

• Sperm are attracted by a chemical released from the egg.

• The head of one of the sperm enters the egg.

• If there is no egg, sperm die within five days.

Fertilisation

• Nucleus of a sperm joins/fuses with the nucleus of an egg.

• Takes place in the fallopian tube.

• Fertilized egg forms a single cell called a zygote.

Pregnancy

• Zygote goes through cell divisions to form a ball of cells, then an embryo.

• Within a few days of fertilisation, the embryo becomes attached to the lining of the uterus (implantation).

• Embryo becomes surrounded by a membrane called the amnion, which fills with amniotic fluid (shock absorber).

• After 8 weeks, the embryo becomes a foetus.

• Pregnancy normally lasts 40 weeks (9 months).

Placenta

• Baby’s blood passes through the umbilical cord to and from the placenta.

• Allows materials to pass between the mother and the baby.

• These materials pass by diffusion.

  • Food and oxygen pass from the mother’s blood into the baby’s blood.

  • Waste products (carbon dioxide and salts) pass from the baby to the mother.

  • Harmful substances (e.g., alcohol, smoke, drugs) can also pass into the baby.

Birth

Stage 1

• Muscles in the uterus contract (labor).

• The amnion bursts.

• Release of the amniotic fluid is ‘the breaking of the waters.’

Stage 2

• The cervix widens.

• The baby is pushed head first out through the cervix and the vagina.

• The umbilical cord is clamped and cut.

• The baby starts to breathe through its lungs.

Stage 3

• The uterus continues to contract.

• The placenta and the remains of the umbilical cord are pushed out of the vagina (afterbirth).

• The remains of the umbilical cord fall away from the baby’s navel after about 7 days.

Growth of the Baby

• Breast milk: Ideal nutrients + antibodies.

Medical, Ethical, and Societal Issues Surrounding Sexual Reproduction

• Contraception

• In vitro fertilisation (IVF)

• Stem cells

Contraception

• Deliberate use of artificial methods to prevent pregnancy.

• Two main types:

  • Preventing fertilisation

  • Preventing implantation

Preventing Fertilisation

• Natural methods: Avoiding intercourse during the fertile period.

• Artificial methods:

  • Contraceptive pill (stops the female from producing eggs).

  • Condom (covers the penis).

  • Cap (covers the cervix).

  • Chemical creams or foams (kill sperm).

  • Medical operations (sperm ducts or fallopian tubes are cut and sealed).

Preventing Implantation

• Pills that stop the embryo from attaching.

• T-shaped device inserted in the uterus.

Ethical Issues

• Some couples find certain contraceptive methods unacceptable due to reliability, ethical concerns, or religious beliefs.

Societal Issues

• Different societies have different views on contraception, often reflected in laws.

In Vitro Fertilisation (IVF)

• Infertility: Inability to have offspring. IVF allows some couples to have a child.

• Taking eggs from the female and sperm from the male, allowing them to fertilize outside the body.

• One (or more) of the embryos is placed into the uterus of the female.

Advantages of IVF

• Allows a couple unable to achieve fertilisation naturally to have a child.

• The child develops normally in the uterus.

Disadvantages of IVF

• Risk of multiple pregnancies (premature births or low birth weight).

• Side effects of drugs.

• Higher risk of birth defects.

• Costly process that often does not result in pregnancy.

Ethical Issues

• Some people feel that IVF is wrong due to:

  • It is not a natural process.

  • Not all embryos are used.

  • Increased risk of birth defects.

Societal Issues

• Different societies have different views on IVF, often reflected in laws.

Stem Cells

• Stem cells: Cells that can develop into any type of body cell.

• Used to learn about body formation and test new drugs.

• Potential treatments for spinal cord injuries, heart diseases, strokes, Parkinson’s disease, etc.

• Sources: 3- to 5-day-old embryos, umbilical cords, adult sources (bone marrow, fat, nose cells).

Ethical Issues

• Embryonic stem cells: Often obtained from embryos left over after IVF treatment.

• Some believe this is wrong as it destroys a potential life.

• Others feel the benefits outweigh this issue.

Societal Issues

• Different societies have different views on the use of stem cells.

• The conflict of two sets of values:

  • Prevent or reduce suffering

  • Respect the value of human life

• Some countries ban all stem cells, others legalize all, others legalize non-embryonic stem cells.

• New and evolving issue

Acids and Bases

Acids

• Acids are substances that have a sour taste.

• Examples: lemon juice (citric acid), vinegar (ethanoic acid).

• Acids found in the laboratory are usually strong acids, so use caution.

• A substance that is an acid is said to be acidic.

• Everyday acids: Lemon juice, rainwater, vinegar.

• Laboratory acids: Hydrochloric acid (HCl), sulfuric acid (H2SO4).

Bases

• Bases are the chemical opposite of acids.

• Examples: bleach, washing soda, oven cleaner, toothpaste.

• A substance that is a base is said to be basic.

• Some bases are corrosive and dangerous like acids.

• Alkalis are bases that dissolve in water.

• A substance that is an alkali is said to be alkaline.

• Neutral substances: Substances that are neither acid nor base, including water and salt solution.

• Everyday bases: Toothpaste, bleach, indigestion tablets.

• Laboratory bases: Sodium hydroxide (NaOH), calcium carbonate (CaCO3), Limewater Ca(OH)2

Indicators

• Indicators are chemicals that show, by means of a colour change, whether a substance is an acid or a base.

• Types of indicators:

  • Litmus paper

  • Universal indicator

Litmus Indicator

• Litmus paper is paper that has been treated with a water-soluble mixture of different dyes from lichens.

• Blue litmus paper turns red in acids.

• Red litmus paper turns blue in bases (or alkalis).

Universal Indicator

• Universal indicator is a mixture of dyes that change to different colours according to how strong the acid or base is.

• Universal indicator gives a range of colours, which can be used to give a value on the pH scale.

pH Scale

• pH scale is from 0 to 14 and it compares the strengths of acids and bases.

  • 0‒7 is an acid (lower the number, the more acidic it is).

  • 7 is neutral (pure water has a pH of almost 7).

  • 7‒14 is an alkali (the higher the number, the greater the alkalinity).

• The pH can be measured using a pH meter or universal indicator.

• Household substances and their position on the pH scale

• * Battery – pH 1–2

• * Vinegar – pH 3–4

• * Lemon – pH 4–6

• * Toothpaste – pH 8–9

• * Water – pH 7

• * Washing powder – pH 9–10

Reactions of Acids

• Acids react with many substances, always producing a salt.

Acid and Metal

• Acids react with a metal to produce a salt and hydrogen gas.

• $\text{metal} + \text{acid} \rightarrow \text{salt} + \text{hydrogen}$

• Naming the salt: first part is the name of the metal, the second is based on the acid used.

  • Zinc + hydrochloric acid → zinc chloride + hydrogen

  • Zinc + nitric acid → zinc nitrate + hydrogen

  • Zinc + sulfuric acid → zinc sulfate + hydrogen

• Test for hydrogen: Place a lighted splint into the test tube; hydrogen is flammable, and you will hear a distinctive ‘squeaky pop’ sound if hydrogen is present.

Neutralisation

• Acids and bases react together and neutralise (cancel) each other to produce a salt and water. Salt and water are neutral.

• $\text{HCL} + \text{NaOH} \rightarrow \text{NaCl} + \text{H2O}$

• $\text{an acid} + \text{a base} \rightarrow \text{a salt} + \text{water}$

• Titrations allow you to find out exactly how much acid is needed to neutralise a base.

Particle Theory Explanation of Neutralization

• Laboratory acids have one atom in common: the hydrogen atom.

  • Hydrochloric acid (HCl)

  • Nitric acid (HNO3)

  • Sulfuric acid (H2SO4)

Acid dissociation in water

• When laboratory acids are dissolved in water, the hydrogen atoms separate from the other atoms to make solution acidic.

• The more hydrogen ions (H+) there are, the lower the pH will be.

• Acids are compounds that dissociate (break) into their ions when placed in water.

• HCl → H+1 + Cl−1

Base dissociation in water

• The common laboratory base sodium hydroxide (NaOH) will also dissociate when added to water.

• $\text{NaOH} \rightarrow \text{Na+1} + \text{OH‒1}$

Neutralization (Ions Rearranged)

• When you add an acid to a base they neutralize – all the ions are rearranged and the products salt and water are formed.

• $\text{H+} + \text{OH‒1} \rightarrow \text{H2O}$

• $\text{Na+1} + \text{Cl‒1} \rightarrow \text{NaCl}$

Acid and carbonate

• Acids can also be neutralized by reacting them with carbonates (which are also bases).

• $\text{an acid} + \text{a carbonate} \rightarrow \text{salt} + \text{water} + \text{carbon dioxide}$

Biochemical Processes

Definition

• A biochemical process is a chemical reaction (or series of chemical reactions) that takes place in a living thing.

• Respiration and photosynthesis are biochemical processes.

• They both involve energy conversions: In respiration, energy is released from food In photosynthesis energy is used to make food.

Respiration

• It is the release of energy from food.

• If it needs oxygen, it is called aerobic respiration; if not, it is anaerobic respiration.

• $\text{food} \rightarrow \text{energy} \qquad \text{respiration}$

Aerobic Respiration

• Living things need energy to move, grow, stay warm, and repair damaged parts, which they get from food in a process called respiration.

• For the majority of living things respiration is aerobic.

• $\text{glucose} + \text{oxygen} \rightarrow \text{carbon dioxide} + \text{water} + \text{energy}$

• Glucose is carried by blood plasma from the small intestine to all the cells of the body, Oxygen is carried by haemoglobin in red blood cells from the lungs to all the cells of the body.

• In living cells- glucose + oxygen = energy + waste products(CO2 & water vapor)

• Aerobic respiration starts in the cytoplasm of a cell but finishes (and releases most of the energy) in the mitochondria.

Factors Affecting Respiration

• Temperature

• Oxygen

• Water

• Temperature: biological reactions are controlled by enzymes (proteins). Above a certain temperature enzymes change shape- dont work well >reaction slows down (humans= enzyme peak- 37°C, plants= 20-30°C)

• Oxygen :Lack of oxygen, cells respire anaerobically(break down glucose w/o O2- small amount of extra energy, dangerous waste products)

• Anaerobic respiration formula: glucose → lactic acid + a small amount of energy.

• In yeast: glucose → alcohol + carbon dioxide + a small amount of energy

• Water : Essential to allow enzymes to work, lack of water slows down the rate of respiration (sweating).

Products of Respiration

• Energy, Carbon Dioxide & Water (Vapor).

• Energy- more active, the more an organism respirates.

• Carbon Dioxide- waste product of respiration; released into the air.

  • Plants may use some carbon dioxide for photosynthesis but whats not used is released into the atmosphere.

• Water : waste product- released into the air

Photosynthesis

• Plants use solar energy to make food.

• light → chemical energy / photosynthesis

Summary of photosynthesis

CO2 + Light + Water --> Glucose + Oxygen.

• $\text{carbon dioxide} + \text{water} \rightarrow \text{glucose} + \text{oxygen}$

Factors affecting photosynthesis:

• Light- energy needed to form food; sunlight is absorbed by the leaves.

• Carbon Dioxide- if plants dont get it photosynthesis will slow down

• Water- if enzymes don't work, photosynthesis cant take place

• Chlorophyll- catalyst - speeds up reaction without being used. (Plants that lack it are yellow and undergo photosynthesis less).

• Temp- enzymes control this. Ideal enzyme temp is 20-30°C.

Products of Photosynthesis:

• Glucose - is the food manufactured