Year 9 Semester 1 Science Examination Revision

Includes Atoms, Cell Biology, Energy

What is the definition of energy?

The ability to do work.

What unit is energy measured in?

Joules (J).

State the Law of Conservation of Energy.

Energy cannot be created or destroyed; it can only be transferred or transformed.

What is the difference between energy transfer and energy transformation?

Energy transfer is when energy moves from one object to another, staying in the same form. Energy transformation is when energy changes into other forms.

What is wasted or unwanted energy?

Energy that is produced during a transfer or transformation but is not useful.

What is the formula for calculating energy efficiency?

Efficiency = (useful energy output / total energy input) x 100%

What is a Sankey diagram?

A diagram where the width of an arrow shows the size of the energy flow. It was first published by Captain Matthew Henry Phineas Riall Sankey in 1898.

What are the three methods of heat transfer?

Conduction, convection, and radiation.

Describe conduction.

The transfer of heat between substances that are in direct contact with each other. It occurs when particles gain energy and vibrate, transferring energy to neighbouring particles.

Describe convection.

The transfer of thermal energy in liquids and gases where warmer, less dense areas rise and cooler, denser areas sink, creating a circulation pattern.

Describe radiation.

The transfer of heat that does not require a medium; it can be transmitted through empty space as thermal radiation (infrared radiation).

What materials are good conductors of heat?

Metals.

What materials are good insulators of heat?

Materials like plastic, wood, and Pink Batts.

What does it mean if an object is a good absorber of radiant heat?

The object will have its temperature increase. Black, dull objects are good absorbers.

What does it mean if an object is a good reflector of radiant heat?

The object's temperature will not change quickly. Shiny, light-colored objects are good reflectors.

How do double-glazed windows reduce heat loss?

They reduce heat loss by conduction (a layer of trapped air/gas acts as an insulator) and convection (gaps between panes limit air movement).

How does a thermos flask reduce heat loss by conduction?

It uses a plastic stopper (poor conductor) and a vacuum (no particles to conduct heat).

How does a thermos flask reduce heat loss by convection?

It uses a vacuum (no particles to form convection currents) and a stopper that prevents hot air from escaping.

How does a thermos flask reduce heat loss by radiation?

The silvered surfaces reflect infrared radiation back towards the contents.

In a hangi, where does heat transfer by conduction occur?

Within the stones; between hot stones; between stones and air; between touching pieces of food.

In a hangi, where does heat transfer by convection occur?

In the hot steam region.

In a hangi, where does heat transfer by radiation occur?

Mainly from the hot stones.

What is the current percentage of renewable electricity in New Zealand?

Approximately 80–85%.

What is New Zealand's goal for renewable electricity?

100% renewable electricity.

What are the three main renewable energy sources in New Zealand mentioned?

Geothermal, wind, and hydroelectric.

What role does geothermal energy play in NZ's electricity grid?

It provides continuous baseload electricity.

What is a major limitation of geothermal energy?

It is location-specific (mainly in the Taupō Volcanic Zone).

What is an advantage of wind energy?

It has very low emissions and large expansion potential.

What is a major challenge for wind energy?

It is intermittent and requires storage or backup power.

What role does hydroelectric power play in NZ's energy system?

It is the largest electricity contributor and provides flexible backup for wind.

What is a challenge for hydroelectric power?

Drought risk.

What is hydrogen?

An element and an energy carrier (to store and transport energy), but not an energy source.

What is green hydrogen?

Hydrogen produced by electrolysis (splitting water into hydrogen and oxygen) using electricity from renewable sources.

What is grey hydrogen?

Hydrogen produced using fossil gas (through steam methane reforming), which produces significant carbon emissions.

What is blue hydrogen?

Hydrogen produced using emissions-intensive methods like steam methane reforming, but with some of the CO2 captured.

What is electrolysis?

The process of splitting water into hydrogen and oxygen gas using electricity.

What are the potential uses of green hydrogen?

Heavy transport (trucks, buses), industrial heat, making climate-friendly fertilisers and steel, and as a possible export industry.

What is a major challenge for using green hydrogen in NZ?

The production cost, energy losses in production, and the need for new infrastructure.

What is the estimated annual hydrogen requirement for NZ to meet its climate ambitions?

About 150 petajoules of hydrogen each year, which is about a quarter of NZ's current energy use.

How much water would be consumed annually to produce this hydrogen?

About 13 million tonnes of water each year.

How does this water consumption compare to Auckland's water demand?

It is the equivalent of a month's worth of Auckland's water demand.

Why is storing hydrogen in high-pressure tanks considered impractical for NZ?

We would need more tanks than we have people. They would be costly, cover large areas of land, and be prone to damage by natural hazards.

What is a potential solution for storing large amounts of hydrogen in NZ?

Storing hydrogen underground in great caverns carved in salt or in old oil and gas fields.

What are some potential risks associated with underground hydrogen storage?

Hydrogen can react with certain types of rock, be consumed by hungry microbes, some injected gas may never come back out (cushion gas), and some may escape into the atmosphere through small cracks.

Why is it important to engage with iwi and hapū when developing green hydrogen infrastructure?

Freshwater has enormous significance to iwi and hapū, and their views on hydrolysis as a consumptive water use need to be understood and addressed to ensure the technology fits appropriately within NZ society.

What existing method in Taranaki is used to store natural gas?

Gas is injected into an old field called Ahuroa and then extracted as required.

What are the characteristics of living things (MRS GREN)?

Movement, Respiration, Sensitivity, Cells, Growth, Reproduction, Excretion, Nutrition.

What is a cell?

The basic structural and functional unit of all living organisms.

What is the function of the cell membrane?

To control what enters and leaves the cell. It is a partially permeable membrane.

What is the function of the cytoplasm?

A jelly-like substance where many chemical reactions take place.

What is the function of the nucleus?

To contain the genetic material (DNA) and control the activities of the cell.

What is the function of the mitochondria?

The site of aerobic respiration, where energy is released from glucose.

What is the function of ribosomes?

The site of protein synthesis.

What is the function of the cell wall?

A rigid outer layer that provides support and maintains the shape of the cell (found in plant cells).

What is the function of chloroplasts?

To contain chlorophyll and are the site of photosynthesis (found in plant cells).

What is the function of the large vacuole?

A fluid-filled sac (containing cell sap) that helps maintain turgor pressure and stores substances (found in plant cells).

List three differences between a plant cell and an animal cell.

Plant cells have a cell wall, chloroplasts, and a large vacuole; animal cells do not have these structures.

What is the function of a neuron?

To transmit electrical signals. It has long extensions for this purpose.

What is the function of a red blood cell?

To carry oxygen around the body.

What is the function of a root hair cell?

To absorb water and minerals from the soil. It has a large surface area for this purpose.

What is the function of a palisade cell?

To carry out photosynthesis. It contains many chloroplasts.

What is the function of xylem cells?

To transport water from the roots to the rest of the plant.

What is the function of phloem cells?

To transport sugars (like sucrose) from the leaves to the rest of the plant.

What is a tissue?

A group of similar cells that work together to perform a specific function.

What is an organ?

A structure made of different tissues working together to carry out a function.

What is an organ system?

A group of organs that work together to perform a major body function.

What is the correct order of organisation from simplest to most complex?

Cells → Tissues → Organs → Organ Systems → Organism.

What are the main steps to view a specimen under a light microscope?

Place the specimen on a slide with a coverslip, place it on the stage, start with the lowest magnification, focus using the coarse then fine adjustment knob.

What are the rules for biological drawings?

Use a pencil, draw clear single lines with no shading, make the drawing large, label with ruled lines, and include a title and magnification.

What is the formula for calculating magnification?

Magnification = Image size ÷ Actual size.

What is the word equation for aerobic respiration?

Glucose + Oxygen → Carbon Dioxide + Water + Energy (ATP).

What is the purpose of respiration?

To release energy from food for processes like movement, growth, and active transport.

What is a key difference between aerobic and anaerobic respiration?

Aerobic respiration uses oxygen and releases a relatively large amount of energy. Anaerobic respiration does not use oxygen and releases a smaller amount of energy.

What is an atom?

The smallest unit of matter with unique characteristics of an element.

What is the charge and relative mass of a proton?

Charge: +1, Relative Mass: 1.

What is the charge and relative mass of an electron?

Charge: -1, Relative Mass: ~0 (1/2000).

What is the charge and relative mass of a neutron?

Charge: 0, Relative Mass: 1.

What is the nucleus of an atom?

The centre of the atom, composed of protons and neutrons, and possessing most of the mass.

What is an element?

A substance that contains just one type of atom.

What is the atomic number?

The number of protons in the nucleus of an atom. It identifies the element.

What is the mass number?

The total number of protons and neutrons in the nucleus of an atom.

What is an ion?

An atom that has gained or lost electrons to obtain a full, stable outer shell.

What is an isotope?

Atoms of the same element with the same number of protons but a different number of neutrons.

What is the periodic table?

A table that arranges elements in order of increasing atomic number, showing repeating patterns in their properties.

What is a group (in the periodic table)?

A vertical column. Elements in the same group have similar properties and the same number of valence electrons.

What is a period (in the periodic table)?

A horizontal row. The period number shows how many electron shells an atom has.

What is a physical property?

A characteristic that can be observed without changing the substance into a new substance, e.g., melting point, state of matter.

What is a chemical property?

A characteristic that describes how a substance reacts to form a new substance, e.g., reactivity with water or acid.

What is a molecule?

A group of two or more atoms chemically bonded together, forming the smallest unit of a substance that can exist independently.

What is a compound?

A substance made of two or more different atoms chemically combined.

What is a mixture?

A substance made of two or more different elements or compounds that are not chemically combined.

What is a fair test?

An experiment where only one variable (the independent variable) is changed and all others are kept the same.

What is the independent variable?

The variable that is changed on purpose by the scientist.

What is the dependent variable?

The variable that is measured or observed as a result of the change.

What are fixed/controlled variables?

Variables that are kept the same to ensure a fair test.

What are the physical properties of Group 1 (Alkali Metals)?

Soft metals, low density, good conductors, low melting points.

What are the chemical properties of Group 1 (Alkali Metals)?

Very reactive with water and oxygen, reactivity increases down the group.

What are the physical properties of Transition Metals?

High melting points, high density, hard, strong, malleable, and good conductors.

What are the chemical properties of Transition Metals?

Less reactive than Group 1, can form multiple oxidation states (e.g., Fe²⁺, Fe³⁺), and form coloured compounds.

What are the physical properties of Group 7 (Halogens)?

Exist as diatomic molecules (F₂, Cl₂, Br₂, I₂), low melting and boiling points, and are poor conductors.