science yr 8 assessment

Question (Front)

Answer (Back)

What is an element?

A pure substance made of only one type of atom.

What is an atom?

The smallest unit of an element that retains the properties of that element.

Name five elements found in everyday life.

Oxygen (air), hydrogen (water), carbon (living things), iron (tools/structures), and copper (wires).

What is the chemical symbol for oxygen?

O

What is the chemical symbol for hydrogen?

H

What is the chemical symbol for carbon?

C

What is the chemical symbol for iron?

Fe

What is the chemical symbol for copper?

Cu

What is the chemical symbol for aluminium?

Al

What is the chemical symbol for gold?

Au

What is the chemical symbol for silver?

Ag

What is the chemical symbol for helium?

He

What is a physical property?

A feature that can be observed or measured without changing what a substance is, such as colour, hardness or melting point.

What is conductivity?

How well a material carries heat or electricity.

What is lustre?

How shiny or reflective a material looks.

What does malleable mean?

Able to be hammered or rolled into thin sheets without breaking.

What does ductile mean?

Able to be stretched or drawn into a wire without breaking.

What are the usual properties of metals?

Usually shiny, strong, good conductors of heat and electricity, malleable and ductile. Most are solid at room temperature.

Which metal is liquid at room temperature?

Mercury (Hg).

Which two common metals are not silver-grey?

Gold and copper.

What are the usual properties of non-metals?

Often dull, poor conductors of heat and electricity, and not malleable. They can be solids, liquids or gases.

What is an insulator?

A material that does not conduct heat or electricity well.

What is a metalloid?

An element with some properties of metals and some of non-metals.

Why are metalloids useful in electronics?

They can act as semiconductors, conducting electricity under certain conditions. Silicon is used in computer chips.

What is an alloy?

A mixture of two or more metals, or a metal with another element, made to improve properties.

What is a compound?

A substance formed when two or more different elements are chemically joined.

What is a mixture?

Two or more substances physically combined but not chemically joined.

Why is copper used for electrical wires?

It conducts electricity well and can be drawn into wires because it is ductile.

Why is aluminium useful for some transport and structures?

It is lightweight and useful where a lower mass is helpful.

Why is steel used in buildings and tools?

It is strong and durable; it is an alloy based mainly on iron.

Why is silicon used in computer chips?

It is a metalloid and semiconductor, so its electrical conductivity can be controlled.

What is a subatomic particle?

A particle smaller than an atom; protons, neutrons and electrons are subatomic particles.

Where are protons found, and what are their charge and relative mass?

In the nucleus; charge +1; relative mass about 1.

Where are neutrons found, and what are their charge and relative mass?

In the nucleus; charge 0; relative mass about 1.

Where are electrons found, and what are their charge and relative mass?

In electron shells around the nucleus; charge −1; relative mass is very small, about 1/1836 of a proton.

What is the nucleus?

The dense centre of an atom, containing protons and neutrons.

What is the atomic number?

The number of protons in the nucleus.

What does the mass number tell you?

The total number of protons and neutrons in an atom.

How do you calculate neutrons in an atom?

Neutrons = mass number − atomic number.

How many electrons does a neutral atom have?

The same number as protons.

How are electrons arranged in the first 18 elements?

In shells: the first shell holds up to 2 electrons, the second up to 8, and the third up to 8 for these first 18 elements.

What are the shell arrangements of the first 10 elements?

H 1; He 2; Li 2,1; Be 2,2; B 2,3; C 2,4; N 2,5; O 2,6; F 2,7; Ne 2,8.

What are the shell arrangements of elements 11–18?

Na 2,8,1; Mg 2,8,2; Al 2,8,3; Si 2,8,4; P 2,8,5; S 2,8,6; Cl 2,8,7; Ar 2,8,8.

What changes as atomic number increases from one element to the next?

The number of protons increases by one; in a neutral atom, the number of electrons also increases by one.

What did Dalton's atomic model suggest?

Atoms were tiny solid spheres, and each element had its own type of atom.

What did Thomson discover and propose?

He discovered the electron and proposed the 'plum pudding' model, with negative electrons inside a positively charged sphere.

What did Rutherford's gold-foil experiment show?

Most of the atom is empty space, with a tiny, dense, positively charged nucleus.

What did Bohr's model add?

Electrons occupy specific energy levels or shells around the nucleus.

How did technology improve atomic models?

New experiments and instruments provided evidence about particles and how atoms are structured, allowing models to become more detailed.

How is the periodic table organised?

By increasing atomic number, in rows called periods and columns called groups.

What do elements in the same group usually have in common?

Similar chemical properties because they have the same number of outer-shell (valence) electrons.

What does a period tell you about an element's electron arrangement?

The period number indicates the number of occupied electron shells in the basic school model.

Where are metals, non-metals and metalloids found on the periodic table?

Metals are mainly on the left and centre; non-metals are mainly on the right; metalloids lie near the staircase boundary.

What is reactivity?

How easily a substance reacts with other substances.

How does position in the periodic table help predict properties?

An element's group and period give clues about its outer electrons, likely reactions and whether it is a metal, non-metal or metalloid.

Who developed an early periodic table and how did he organise it?

Dmitri Mendeleev arranged elements mainly by atomic mass and similar properties, leaving gaps for elements not yet discovered.

What did Moseley change about the periodic table?

He organised elements by atomic number rather than atomic mass.

What does a chemical symbol represent?

A particular element; symbols use one or two letters, with the first letter capitalised and the second, if present, lowercase.

What elements are in water, H₂O?

Hydrogen and oxygen; each water molecule has 2 hydrogen atoms and 1 oxygen atom.

What elements are in carbon dioxide, CO₂?

Carbon and oxygen; each molecule has 1 carbon atom and 2 oxygen atoms.

What elements are in sodium chloride, NaCl?

Sodium and chlorine, in a 1:1 ratio in the formula unit.

What does a subscript in a chemical formula tell you?

How many atoms of that element are in the formula; for example, the 2 in CO₂ means two oxygen atoms.

What does a flame test do?

Heats a sample and uses the flame colour to help identify certain metal ions/elements.

What does the glowing splint test identify?

Oxygen; a glowing splint relights if oxygen is present.

What does the lit-splint pop test identify?

Hydrogen; it can make a squeaky pop. This test should only be done under teacher supervision.

How can you compare mystery elements in a school investigation?

Measure properties such as density and melting/boiling point, observe flame colour, and compare several results with known data.

How do availability and cost affect a material's use?

A material may be chosen because it is available, affordable and has the right properties; a rare or expensive material may be reserved for specialised uses.

What is energy?

The ability to do work or cause things to move, heat up, light up or change.

What is kinetic energy (KE)?

Energy an object has because it is moving.

What is potential energy (PE)?

Stored energy, for example because of an object's position or shape.

What is gravitational potential energy?

Stored energy an object has because it is raised above the ground; greater height means more stored energy.

What is elastic potential energy?

Energy stored when an object is stretched or squashed, such as a spring or rubber band.

What is chemical energy?

Energy stored in substances such as food, fuels and batteries.

What is thermal energy?

Energy associated with the temperature of an object or substance.

What is energy transfer?

Energy moving from one object or place to another without changing its form.

What is energy transformation?

Energy changing from one form to another.

What is conduction?

Energy transfer through direct contact between particles, especially in solids.

What is convection?

Energy transfer by the movement of warmer and cooler fluids, such as liquids or gases.

What is radiation?

Energy transfer by waves; it can travel through empty space, such as sunlight reaching Earth.

How can you remember conduction, convection and radiation?

Conduction = contact; convection = moving fluid; radiation = waves.

What is the law of conservation of energy?

Energy cannot be created or destroyed; it can only be transferred or transformed, so the total amount remains the same.

What energy transformations happen in a light bulb?

Electrical energy transforms into light energy and thermal (heat) energy.

What energy transformations happen when a bow is released?

Elastic potential energy transforms mainly into kinetic energy, with some sound and heat.

What energy transformations happen in a solar panel?

Radiant energy from the Sun is transformed into electrical energy.

What energy transformations happen in photosynthesis?

Light energy from the Sun is stored as chemical energy in glucose.

What energy transformations happen in a falling object?

Gravitational potential energy transforms into kinetic energy as it falls; some energy may also transfer as sound and heat.

What is an open system?

A system that can exchange both matter and energy with its surroundings.

What is a closed system?

A system that can exchange energy but not matter with its surroundings.

Give an example of an open system and explain why.

A dog: food, water and air enter; waste, carbon dioxide and heat leave.

Give an example of a closed system and explain why.

A battery-operated flashlight: energy leaves as light and heat, but matter does not enter or leave during normal operation.

What are input, useful and wasted energy?

Input energy enters a system; useful energy is the wanted output; wasted energy is not useful and is often released as heat or sound.

Why does a bouncing ball bounce to a lower height each time?

Some energy is transferred to the surroundings as heat and sound, leaving less energy for the next bounce.

What is a physical change?

A change in state, size or shape where no new substance is formed; often reversible.

What is a chemical change?

A change in which one or more new substances form.

What are common signs of a chemical reaction?

Colour change, gas bubbles, a precipitate (solid) forming, temperature change, light or a new smell. One sign alone does not always prove a reaction.

What is a reactant?

A starting substance in a chemical reaction.

What is a product?

A substance formed by a chemical reaction.

How is a word equation written?

Write the names of the reactants on the left and the names of the products on the right, with an arrow meaning 'produces'.

Write the word equation for cellular respiration.

Glucose + oxygen → carbon dioxide + water + energy.