Chemistry 8D-8F

What is an independent variable?

The variable for which values we decide to change.

What is a dependent variable?

The variable whose value we measure.

What are control variables?

The variables which must be kept the same (constant).

What is an element?

A pure substance that cannot be broken down into any other substances, made from just one type of atom.

What is a compound?

A substance made from more than one different type of element chemically bonded together in a fixed ratio.

What does it mean if a compound name ends in "-ide"?

It contains just two elements.

What does it mean if a compound name ends in "-ate"?

It contains three or more elements, one of which is oxygen.

What happens to atoms and their total number during a chemical reaction?

Atoms are rearranged, but the total number of atoms does not change.

What is a chemical reaction?

When chemical bonds are broken and made between atoms, so that new substances are made.

What do word equations show, and how are they structured?

They show what happens in a chemical reaction. Structured as: Reactants -> Products.

On which sides of a chemical equation arrow are reactants and products located?

Reactants are on the left; products are on the right.

Why is an arrow used instead of an equals sign (=) in a chemical equation?

It represents that the reactants are changing into a new substance.

What happens in a combustion reaction?

A fuel is burned and reacts with oxygen to release energy.

What is an oxidation reaction?

A reaction where a substance reacts with oxygen and produces oxides (e.g., combustion).

What reactant is always on the left side of a combustion equation?

Oxygen.

What are the typical products written on the right side of a complete combustion equation?

Carbon dioxide and water.

When does complete combustion of a hydrocarbon occur and what does it release?

Occurs when there is a good supply of oxygen. It releases the maximum amount of energy, carbon dioxide, and water.

When does incomplete combustion occur and what is its energy output?

Occurs when there is a poor supply of oxygen. Less energy is released.

What products can be formed during incomplete combustion instead of carbon dioxide?

Carbon monoxide, particulate carbon (soot), or a mixture of both.

Why is carbon monoxide dangerous to the human body?

It is a poisonous gas that binds to haemoglobin in red blood cells, preventing them from carrying oxygen.

Why is carbon monoxide difficult to detect?

It is colourless and has no smell.

What are the products when an acid reacts with a metal?

A salt and hydrogen (Metal + Acid -> Salt + Hydrogen).

What visible observations show a metal is reacting with an acid?

The metal gets smaller (used up) and bubbles of gas are observed.

What is the chemical test for hydrogen gas?

Place a burning splint into the tube; a small explosion occurs making a "squeaky pop" sound.

What determines how fast a metal reacts with an acid?

The reactivity of the metal (more reactive = faster reaction).

What are the two rules for naming a salt?

1. First word is the name of the metal. 2. Second word comes from the acid.

What salt name ending comes from Hydrochloric acid?

Chloride.

What salt name ending comes from Nitric acid?

Nitrate.

What salt name ending comes from Sulfuric acid?

Sulfate.

What is a displacement reaction?

A reaction where a more reactive element displaces a less reactive element out of its compound.

What happens when magnesium is dipped into a blue copper sulfate solution?

A displacement reaction occurs, producing copper and magnesium sulfate solution.

What visual or physical signs should you look for to observe a displacement reaction?

A colour change or a change in temperature.

What practical use do displacement reactions have in industry?

They can be used to extract metals from their compounds (oxides).

What is the reactivity series?

An arrangement of metals in order of their reactivity.

Which metals from the series cannot be extracted using carbon?

Potassium, Sodium, Calcium, Magnesium, Aluminium.

Which metals from the series can be extracted using carbon?

Zinc, Iron, Tin, Lead, Copper.

What is formed when metals react with water?

Metal hydroxides and hydrogen gas (Metal + Water -> Metal Hydroxide + Hydrogen).

Describe the reaction of Lithium with water.

It floats, moves slowly on the surface, and produces bubbles of hydrogen.

Describe the reaction of Sodium with water.

It melts and floats, moves quickly on the surface, self-ignites, and burns with a yellow flame.

Describe the reaction of Potassium with water.

It melts and floats, moves very quickly, self-ignites, and burns with sparks and a lilac flame.

When does a metal object corrode?

When it is exposed to the open air and water.

What is rusting?

The specific corrosion of iron, forming a weaker, flaky brown compound called iron oxide.

How does calcium chloride prevent corrosion?

It dries out the air.

How does sacrificial protection prevent corrosion?

Covering a metal with a more reactive metal from higher in the reactivity series.

How do paint or grease protect metal from corroding?

They create a physical barrier that stops oxygen/water from reaching the metal.

What is galvanising?

Coating iron in zinc to stop oxygen and water from attacking the iron.

What is the Law of Conservation of Mass?

The total mass of chemicals before and after a reaction remains the same.

What are physical properties?

Properties that tell us the state of a substance, or how it looks, feels, or behaves (e.g., colour, density, melting point).

What is a mixture?

Two or more different elements or compounds that are not chemically bonded together.

Give 4 examples of mixtures.

Air, sea water, iron and sulphur, or solutions.

What is a pure substance?

A single type of substance with nothing mixed in it.

What is a solute?

The substance that dissolves in a liquid.

What is a solvent?

The liquid that dissolves a solute.

What is a solution?

A mixture formed when a solute dissolves in a solvent (Solute + Solvent = Solution).

What is a saturated solution?

A solution in which no more solute can dissolve.

What does it mean if a substance is soluble vs insoluble?

Soluble means it is able to dissolve in a liquid; insoluble means it is unable to dissolve.

What does solubility refer to?

How well a substance dissolves.

What processes can separate mixtures?

Physical processes: filtration, crystallisation, simple distillation, fractional distillation, and chromatography.

What is crystallisation used for and how does it work?

To obtain salt crystals from a solution by gently evaporating the water out.

Why does filtration work?

Insoluble solid particles are too large to pass through the small holes in the filter paper.

Define residue and filtrate in filtration.

Residue is the solid left on the filter paper; filtrate is the liquid that passes into the flask.

What equipment is used during filtration?

Filter paper, funnel, and conical flask.

What is distillation used for?

To separate a mixture of two or more liquids, or a soluble solid from a liquid.

What three steps are involved in distillation?

Heating (evaporation), condensation, and collection.

What is the role of a condenser in distillation?

It cools down gas, turning it back into a liquid.

When is chromatography useful?

When you want to separate a mixture of several solids that are soluble.

In chromatography, how does solubility affect how far a dye travels?

The MORE soluble the dye, the further it will travel up the paper.

What are the three layers of Earth's structure?

The crust (rocky outer layer), the mantle (semi-solid middle layer), and the core (innermost layer).

Describe the mantle.

The thickest, semi-solid rock layer below the crust that moves very slowly, like a liquid.

What metals make up the core and what is their state?

Iron and nickel. The inner core is solid, and the outer core is liquid.

What gives Earth its magnetic field?

The magnetic metals (iron and nickel) in the core.

What are the two main gases in Earth's atmosphere and their percentages?

Nitrogen (approx. 78%) and Oxygen (approx. 21%).

What are the three types of rock found on Earth?

Igneous, metamorphic, and sedimentary.

How are grains arranged in sedimentary rocks, and where are the oldest layers?

Arranged in layers; the oldest layers are at the bottom.

Give 4 examples of sedimentary rocks.

Chalk, limestone, shale, and sandstone.

What are the 5 processes that form a sedimentary rock, in order?

Transport -> Deposition -> Sedimentation -> Compaction -> Cementation.

What unique features can sedimentary rocks contain?

Fossils of animals and plants trapped as the rock formed.

How are metamorphic rocks formed?

From other rocks that change due to high heat or pressure without melting.

Give 2 examples and uses of metamorphic rocks.

Marble (decorative statues) and slate (roof tiles).

How are igneous rocks formed?

From molten (liquid) rock that has cooled and solidified.

What is the difference between magma and lava?

Magma is molten rock underground; lava is molten rock that reaches the surface.

Describe the crystal structure of igneous rocks.

They contain randomly arranged interlocking crystals.

How does cooling speed affect igneous crystal sizes?

Fast cooling makes small crystals (extrusive); slow cooling makes large crystals (intrusive).

What is an extrusive igneous rock and what is an example?

Formed from magma/lava cooling quickly on the surface. Example: Obsidian.

What is an intrusive igneous rock and what is an example?

Formed from magma cooling slowly deep underground. Example: Granite.

What is the recycling of rocks called?

The rock cycle.

What are precise measurements?

Measurements where there is little spread about the mean value.

What are accurate measurements?

Measurements that are close to the true value.

What makes an experiment valid?

If it directly answers the question being asked.

When is a measurement repeatable?

If the same person uses the same method/experiment and obtains the same results.

When is a measurement reproducible?

If a different person or group carries out the same experiment and gets the same results.