year 8 science
Explain the need for cells to exchange substances with the environment, particularly in the process of respiration.
Cells: Cells are the basic building blocks of all living things. The human body is composed of trillions of cells. They provide structure for the body, take in nutrients from food, convert those nutrients into energy, and carry out specialised functions.
Cells → Respiration
When we breathe, the respiratory system takes in oxygen and sends out carbon dioxide. The cells in our bodies need fresh oxygen to stay alive. As cells do their jobs, they make and give off carbon dioxide. This exchange of oxygen and carbon dioxide is called respiration.
Explain the reasons living things require food in terms of energy, growth and repair. • Explain the requirements of aerobic respiration • Explain the process of aerobic respiration, including the chemical word equation. • Explain the process of digestion with reference to the function of the main organs involved. • Compare mechanical and chemical digestion • Describe structures in the digestive system that allow for absorption of nutrients. • Explain how the energy in food can be measured, when given a formula.
Nutrient: a substance that provides nourishment essential for the maintenance of life and for growth.
Digestive System: The digestive system is made up of the digestive tract and other organs that help the body break down and absorb food. It is a long, twisting tube that starts at the mouth and goes through the oesophagus, stomach, small intestine, large intestine and anus.
Why do living things require food?
Living things require food in terms of energy, growth and repair as it a basic fundamental requirement for the sustainment of life. Within foods are nutrients, which are substances essential for growth, energy and repair; energy from these nutrients is needed to carry out basic life processes
Aerobic Respiration
Requires oxygen (O2)
During aerobic cellular respiration, glucose reacts with oxygen, forming ATP that can be used by the cell. Carbon dioxide and water are created as byproducts
ATP is an organic compound that our body uses for energy.
💡 Glucose + Oxygen ➡ Carbon Dioxide + Water + Energy
Process of Digestion
Digestion is the breakdown of food into simple nutrients the body can absorb
The digestive system breaks food down into proteins, fats and carbohydrates that are needed by the body
MOUTH: The entry point for food passing into the body; (teeth) biting and chewing help with physical digestion. The tongue works the food into a ball called a bolus, then pushes to the back of mouth to be swallowed. Saliva helps with chemical digestion. This is where the breakdown of most nutrients starts.
OESOPHAGUS: The tube that connects the throat to the stomach. Food is squeezed through the oesophagus by peristalsis, even if you're hanging upside down.
STOMACH: A muscular pouch that churns and squeezes food into liquid; churning and squeezing help with physical digestion. Gastric juices help with chemical digestion. Chyme is a semi-liquid mixture of partially digested food, stomach acid, and digestive enzymes that form in the stomach.
SMALL INTESTINE: A long, narrow tube where the body absorbs most nutrients, the small intestine has a large surface area to absorb nutrients into the bloodstream efficiently
LARGE INTESTINE: A wide tube where water is absorbed and most good bacteria live; good bacteria living in the large intestine help it break down fats and complex carbohydrates
ANUS: At the opening at the end of the digestive tract, solid waste is expelled by the body through the anus.
Mechanical vs Chemical Digestion
Mechanical Digestion
Mechanical digestion involves physically breaking down food substances into smaller particles to more efficiently undergo chemical digestion
The breakdown of food by sources such as the mouth by churning, chewing, and biting
Chemical Digestion
The breakdown of food by saliva enzymes saliva, stomach acid and other digestive juices
Chemical digestion forms new substances, including simple nutrients that can be absorbed by the body, through the small intestine.
Absorption of Nutrients
The movement of substances through tiny holes into the bloodstream. Water and nutrients are absorbed through tiny pores in the lining of the intestines.
The small intestine absorbs most of the nutrients in your food, and your circulatory system passes them on to other parts of your body to store or use. Special cells help absorb nutrients cross the intestinal lining into your bloodstream
Food is then squeezed into the lower parts of the small intestine, called the jejunum and the ileum. Nutrients are absorbed from the ileum, lined with millions of finger-like projections called villi. Each villus is connected to a mesh of capillaries. This is how nutrients pass into the bloodstream.
How can Energy be Measured?
The equation for calculating the energy content of a food source via calorimetry is as follows:
💡 Energy (joules) = Mass of water (g) × 4.2 (J/gºC) × Temperature increase (ºC)
Kilocalories
Identify the structures of the human excretory system. •Describe the functions of the structures of the excretory system. •Describe the role of the excretory system in removing wastes and balancing salt and water in the blood.
Excretory System: The excretory system is a vital biological system that removes excess and waste products from the body to maintain homeostasis. Most of these products are in fact used and broken down components of metabolism that leave the body in the form of urine, sweat, or feces.
Function of the Structure
Kidney: Filters all the impurities out of the blood and removes excess water from the body
Kidneys are in the abdomen, near the liver and stomach, and filter waste products from blood
Ureter: Tubes that carries the urine from the kidney to the bladder
Bladder: Holds urine until it builds up and is released
Anus: Deposits feces
Urethra: Deposits liquid wastes
The bladder receives urine from the kidneys via the ureters and excretes it via the urethra
Salt and Water in the Blood
The urinary system removes waste from your blood in the form of urine
Helps regulate blood volume and pressure, also regulates the levels of salt and chemicals within the body’s blood and cells.
Kidneys remove acid produced by the cells and maintains healthy levels of minerals.
Define energy and how can we detect it • Definition of energy as the ability to make things move and cause changes • Describe types of energy (make a list with examples) • Compare energy transfer and energy transformation
Energy: 1. the strength and vitality required for sustained physical or mental activity
2.power derived from the utilisation of physical or chemical resources, especially to provide light and heat or to work machines
We can detect energy from movement, sound, heat or light as they all are proofs that energy is present and being used
Energy’s Ability to Make Things Move and Change
Energy is defined as the ability to do work
Which technically means that it can cause some kinds of change
Energy that makes things move is “Kinetic Energy”
Types of Energy
Kinetic Energy: Energy which a body possesses by virtue of being in motion
Potential Energy: the energy that is stored in an object due to its position relative to some zero position
Gravitational Potential: energy an object possesses because of its position in a gravitational field
Elastic Potential: energy stored as a result of applying a force to deform an elastic object
Chemical Potential: the energy stored in the chemical bonds of a substance. The various chemicals that make up gasoline contain a large amount of chemical potential energy that is released when the gasoline is burned in a controlled way in the engine of the car
Electrical Energy: the power an atom's charged particles have to cause an action or move an object
Renewable Energy: energy from renewable resources that are naturally replenished on a human timescale
Renewable Solar: Energy created by the heat and light of the sun is called solar energy. Solar power is produced when energy from the sun is converted into electricity
Renewable Wind: Wind turbines harness energy from the wind using mechanical power to spin a generator and create electricity
Thermal Energy: the energy contained within a system that is responsible for its temperature
Energy Transfer
The conversion of one form of energy into another remaining in the same form
A common example of energy moving between objects, called energy transfer, is the transfer of kinetic energy from a moving object to a motionless object. Kinetic energy is the energy of motion. When a bat hits a ball, some of the bat's kinetic energy moves to the ball. However, the energy stays in the same form
Energy Transformation
The changing of forms of energy from one to another
Gasoline (chemical) is put into our cars, and with the help of electrical energy from a battery, provides mechanical (kinetic) energy
Outline the essential elements of an electric circuit. • Compare conductors and insulators. • Identify symbols used in circuit diagrams. • Compare series circuit and parallel circuits. • Draw circuit diagrams to represent simple series circuit and parallel circuit.
Electrical Energy: Electrical energy is the power an atom's charged particles have to cause an action or move an object. The movement of electrons from one atom to another is what results in electrical energy.
Conductors
Electrons in conductors (metals) are free to move
Little to no resistance to the flow of electrons unlike insulators
In a conductor, the outer electrons of the atom are loosely bound and can freely move through the material when an electric charge is applied
Metals, metal alloys, electrolytes, some non-metals such graphite or liquids, including water are good electrical conductors
Insulators
Insulators do not allow electrons to flow through them
Electrons are tightly packed with atoms, not loosely bound like conductors
Many objects made from non-metals are insulators
Plastic and rubber are two very effective insulators
Series
Connected in a one after the other manner
Some currents flow through all the components in the circuit
Different potential voltage exists across each component
Single path
Fault in one of the circuit components causes failure of the whole thing
Less commonly used
Parallel
Components are connected head to head manner
Different current flows through each component in the circuit
The potential voltage across the circuit is equal for the components
Multiple paths
Fault in a single component does not render the circuit unusable
Commonly used in home lighting set ups.
Explain differences between heat and temperature. • Describe heat energy and the three methods of heat transfer, with examples. • Explain convection currents – use models to visualise them. • Describe radiation – for example infra-red and how this is related to the Sun.
Heat Energy: The term "thermal energy" is used loosely in various contexts in physics and engineering, generally related to the kinetic energy of vibrating and colliding atoms in a substance.
Conduction
Solids are usually very good conductors of heat because the particles in them are packed closely together
Gases are the poorest conductors because the particles that they are made of are far apart
Metals are generally good conductors of heat and electricity
Different metals conduct heat to different extents
Non-metals, such as glass, plastics and wood do not conduct as well
Materials that conduct heat and electricity poorly are insulators
Convection
The spread of heat due to the movement of particles in liquids and gases is called convection
Heat travels through liquids and gases by convection
Heat rises, Cold sinks
Radiation
Heat transfer that moves in waves, does not rely on movement of particles
It does not require particles to transfer heat from one place to another
Heat that travels by radiation is called radiation heat
Radiant heat can be reflected, transmitted, or absorbed
Reflection = bounce off/sent back
Transmitted = pass through/broadcast
Absorbed = heat is taken in and temperatures of the surface rise
When a liquid or gas is heated, the particles in the heated region become more spread out, or less dense. Liquid or gas that is less dense than the rest of the substances will rise, taking heat with it. This flow of warm air up and cool air down creates a circular current called convection currents.
Convection currents are the results of differential heating. Less dense (lighter), warm material rises while more dense (heavier) cool material sinks. This is the movement that creates the circular pattern that we see all throughout our world.
Radiation is the emission of energy in the form of waves or particles.
In the context of the Sun, it includes various forms of electromagnetic radiation.
Infrared radiation is a type of electromagnetic radiation with longer wavelengths than visible light, we can only feel it in the form of heat.
The Sun emits infrared radiation along with other types of electromagnetic radiation.
Infrared radiation from the Sun is responsible for heating the Earth and plays a key role in the Earth's greenhouse effect.
Explain the need for cells to exchange substances with the environment, particularly in the process of respiration.
Cells: Cells are the basic building blocks of all living things. The human body is composed of trillions of cells. They provide structure for the body, take in nutrients from food, convert those nutrients into energy, and carry out specialised functions.
Cells → Respiration
When we breathe, the respiratory system takes in oxygen and sends out carbon dioxide. The cells in our bodies need fresh oxygen to stay alive. As cells do their jobs, they make and give off carbon dioxide. This exchange of oxygen and carbon dioxide is called respiration.
Explain the reasons living things require food in terms of energy, growth and repair. • Explain the requirements of aerobic respiration • Explain the process of aerobic respiration, including the chemical word equation. • Explain the process of digestion with reference to the function of the main organs involved. • Compare mechanical and chemical digestion • Describe structures in the digestive system that allow for absorption of nutrients. • Explain how the energy in food can be measured, when given a formula.
Nutrient: a substance that provides nourishment essential for the maintenance of life and for growth.
Digestive System: The digestive system is made up of the digestive tract and other organs that help the body break down and absorb food. It is a long, twisting tube that starts at the mouth and goes through the oesophagus, stomach, small intestine, large intestine and anus.
Why do living things require food?
Living things require food in terms of energy, growth and repair as it a basic fundamental requirement for the sustainment of life. Within foods are nutrients, which are substances essential for growth, energy and repair; energy from these nutrients is needed to carry out basic life processes
Aerobic Respiration
Requires oxygen (O2)
During aerobic cellular respiration, glucose reacts with oxygen, forming ATP that can be used by the cell. Carbon dioxide and water are created as byproducts
ATP is an organic compound that our body uses for energy.
💡 Glucose + Oxygen ➡ Carbon Dioxide + Water + Energy
Process of Digestion
Digestion is the breakdown of food into simple nutrients the body can absorb
The digestive system breaks food down into proteins, fats and carbohydrates that are needed by the body
MOUTH: The entry point for food passing into the body; (teeth) biting and chewing help with physical digestion. The tongue works the food into a ball called a bolus, then pushes to the back of mouth to be swallowed. Saliva helps with chemical digestion. This is where the breakdown of most nutrients starts.
OESOPHAGUS: The tube that connects the throat to the stomach. Food is squeezed through the oesophagus by peristalsis, even if you're hanging upside down.
STOMACH: A muscular pouch that churns and squeezes food into liquid; churning and squeezing help with physical digestion. Gastric juices help with chemical digestion. Chyme is a semi-liquid mixture of partially digested food, stomach acid, and digestive enzymes that form in the stomach.
SMALL INTESTINE: A long, narrow tube where the body absorbs most nutrients, the small intestine has a large surface area to absorb nutrients into the bloodstream efficiently
LARGE INTESTINE: A wide tube where water is absorbed and most good bacteria live; good bacteria living in the large intestine help it break down fats and complex carbohydrates
ANUS: At the opening at the end of the digestive tract, solid waste is expelled by the body through the anus.
Mechanical vs Chemical Digestion
Mechanical Digestion
Mechanical digestion involves physically breaking down food substances into smaller particles to more efficiently undergo chemical digestion
The breakdown of food by sources such as the mouth by churning, chewing, and biting
Chemical Digestion
The breakdown of food by saliva enzymes saliva, stomach acid and other digestive juices
Chemical digestion forms new substances, including simple nutrients that can be absorbed by the body, through the small intestine.
Absorption of Nutrients
The movement of substances through tiny holes into the bloodstream. Water and nutrients are absorbed through tiny pores in the lining of the intestines.
The small intestine absorbs most of the nutrients in your food, and your circulatory system passes them on to other parts of your body to store or use. Special cells help absorb nutrients cross the intestinal lining into your bloodstream
Food is then squeezed into the lower parts of the small intestine, called the jejunum and the ileum. Nutrients are absorbed from the ileum, lined with millions of finger-like projections called villi. Each villus is connected to a mesh of capillaries. This is how nutrients pass into the bloodstream.
How can Energy be Measured?
The equation for calculating the energy content of a food source via calorimetry is as follows:
💡 Energy (joules) = Mass of water (g) × 4.2 (J/gºC) × Temperature increase (ºC)
Kilocalories
Identify the structures of the human excretory system. •Describe the functions of the structures of the excretory system. •Describe the role of the excretory system in removing wastes and balancing salt and water in the blood.
Excretory System: The excretory system is a vital biological system that removes excess and waste products from the body to maintain homeostasis. Most of these products are in fact used and broken down components of metabolism that leave the body in the form of urine, sweat, or feces.
Function of the Structure
Kidney: Filters all the impurities out of the blood and removes excess water from the body
Kidneys are in the abdomen, near the liver and stomach, and filter waste products from blood
Ureter: Tubes that carries the urine from the kidney to the bladder
Bladder: Holds urine until it builds up and is released
Anus: Deposits feces
Urethra: Deposits liquid wastes
The bladder receives urine from the kidneys via the ureters and excretes it via the urethra
Salt and Water in the Blood
The urinary system removes waste from your blood in the form of urine
Helps regulate blood volume and pressure, also regulates the levels of salt and chemicals within the body’s blood and cells.
Kidneys remove acid produced by the cells and maintains healthy levels of minerals.
Define energy and how can we detect it • Definition of energy as the ability to make things move and cause changes • Describe types of energy (make a list with examples) • Compare energy transfer and energy transformation
Energy: 1. the strength and vitality required for sustained physical or mental activity
2.power derived from the utilisation of physical or chemical resources, especially to provide light and heat or to work machines
We can detect energy from movement, sound, heat or light as they all are proofs that energy is present and being used
Energy’s Ability to Make Things Move and Change
Energy is defined as the ability to do work
Which technically means that it can cause some kinds of change
Energy that makes things move is “Kinetic Energy”
Types of Energy
Kinetic Energy: Energy which a body possesses by virtue of being in motion
Potential Energy: the energy that is stored in an object due to its position relative to some zero position
Gravitational Potential: energy an object possesses because of its position in a gravitational field
Elastic Potential: energy stored as a result of applying a force to deform an elastic object
Chemical Potential: the energy stored in the chemical bonds of a substance. The various chemicals that make up gasoline contain a large amount of chemical potential energy that is released when the gasoline is burned in a controlled way in the engine of the car
Electrical Energy: the power an atom's charged particles have to cause an action or move an object
Renewable Energy: energy from renewable resources that are naturally replenished on a human timescale
Renewable Solar: Energy created by the heat and light of the sun is called solar energy. Solar power is produced when energy from the sun is converted into electricity
Renewable Wind: Wind turbines harness energy from the wind using mechanical power to spin a generator and create electricity
Thermal Energy: the energy contained within a system that is responsible for its temperature
Energy Transfer
The conversion of one form of energy into another remaining in the same form
A common example of energy moving between objects, called energy transfer, is the transfer of kinetic energy from a moving object to a motionless object. Kinetic energy is the energy of motion. When a bat hits a ball, some of the bat's kinetic energy moves to the ball. However, the energy stays in the same form
Energy Transformation
The changing of forms of energy from one to another
Gasoline (chemical) is put into our cars, and with the help of electrical energy from a battery, provides mechanical (kinetic) energy
Outline the essential elements of an electric circuit. • Compare conductors and insulators. • Identify symbols used in circuit diagrams. • Compare series circuit and parallel circuits. • Draw circuit diagrams to represent simple series circuit and parallel circuit.
Electrical Energy: Electrical energy is the power an atom's charged particles have to cause an action or move an object. The movement of electrons from one atom to another is what results in electrical energy.
Conductors
Electrons in conductors (metals) are free to move
Little to no resistance to the flow of electrons unlike insulators
In a conductor, the outer electrons of the atom are loosely bound and can freely move through the material when an electric charge is applied
Metals, metal alloys, electrolytes, some non-metals such graphite or liquids, including water are good electrical conductors
Insulators
Insulators do not allow electrons to flow through them
Electrons are tightly packed with atoms, not loosely bound like conductors
Many objects made from non-metals are insulators
Plastic and rubber are two very effective insulators
Series
Connected in a one after the other manner
Some currents flow through all the components in the circuit
Different potential voltage exists across each component
Single path
Fault in one of the circuit components causes failure of the whole thing
Less commonly used
Parallel
Components are connected head to head manner
Different current flows through each component in the circuit
The potential voltage across the circuit is equal for the components
Multiple paths
Fault in a single component does not render the circuit unusable
Commonly used in home lighting set ups.
Explain differences between heat and temperature. • Describe heat energy and the three methods of heat transfer, with examples. • Explain convection currents – use models to visualise them. • Describe radiation – for example infra-red and how this is related to the Sun.
Heat Energy: The term "thermal energy" is used loosely in various contexts in physics and engineering, generally related to the kinetic energy of vibrating and colliding atoms in a substance.
Conduction
Solids are usually very good conductors of heat because the particles in them are packed closely together
Gases are the poorest conductors because the particles that they are made of are far apart
Metals are generally good conductors of heat and electricity
Different metals conduct heat to different extents
Non-metals, such as glass, plastics and wood do not conduct as well
Materials that conduct heat and electricity poorly are insulators
Convection
The spread of heat due to the movement of particles in liquids and gases is called convection
Heat travels through liquids and gases by convection
Heat rises, Cold sinks
Radiation
Heat transfer that moves in waves, does not rely on movement of particles
It does not require particles to transfer heat from one place to another
Heat that travels by radiation is called radiation heat
Radiant heat can be reflected, transmitted, or absorbed
Reflection = bounce off/sent back
Transmitted = pass through/broadcast
Absorbed = heat is taken in and temperatures of the surface rise
When a liquid or gas is heated, the particles in the heated region become more spread out, or less dense. Liquid or gas that is less dense than the rest of the substances will rise, taking heat with it. This flow of warm air up and cool air down creates a circular current called convection currents.
Convection currents are the results of differential heating. Less dense (lighter), warm material rises while more dense (heavier) cool material sinks. This is the movement that creates the circular pattern that we see all throughout our world.
Radiation is the emission of energy in the form of waves or particles.
In the context of the Sun, it includes various forms of electromagnetic radiation.
Infrared radiation is a type of electromagnetic radiation with longer wavelengths than visible light, we can only feel it in the form of heat.
The Sun emits infrared radiation along with other types of electromagnetic radiation.
Infrared radiation from the Sun is responsible for heating the Earth and plays a key role in the Earth's greenhouse effect.
