year 10 mocks combined set

What is the conservation of mass?

In a chemical reaction, atoms are not created or destroyed, just rearranged, so total mass before equals total mass after the reaction.

When a metal forms a metal oxide, why does the mass increase?

Atoms from gaseous oxygen have been added.

When an acid reacts with a metal, why does the mass decrease?

A gas is produced and escapes.

What is relative formula mass?

The sum of the relative atomic masses of each atom in a substance.

What are the four state symbols and what do they stand for?

(s) solid, (l) liquid, (g) gas, (aq) aqueous or dissolved in water.

How can you tell when a symbol equation is balanced?

The number of atoms of each element is the same on both sides.

What is a mole?

Mass of a substance that contains 6.02×10²³ particles.

Give the value for Avogadro's constant.

6.02×10²³.

Which formula is used to calculate the number of moles from mass and M?

Moles = mass / M.

Which formula is used to calculate the mass of a substance from number of moles and M?

Mass = moles × M.

What is a limiting reactant?

The reactant that is completely used up in a chemical reaction.

What is a unit for concentration?

g/dm³ or mol/dm³.

Which formula is used to calculate concentration from mass and volume?

Concentration (g/dm³) = mass (g) / volume (dm³).

Which formula is used to calculate volume from concentration and mass?

Volume (dm³) = mass (g) / concentration (g/dm³).

Which formula is used to calculate mass from concentration in g/dm³ and volume?

Mass (g) = concentration (g/dm³) × volume (dm³).

How can you convert a volume reading in cm³ to dm³?

Divide by 1000.

If the amount of solute in a solution is increased, what happens to its concentration?

It increases.

If the volume of water in a solution is increased, what happens to its concentration?

It decreases.

What is the yield of a reaction?

Mass of product obtained from the reaction.

What is the theoretical yield of a reaction?

Maximum mass of the product that could have been produced.

Why is the actual yield always less than the theoretical yield?

The reaction may be reversible, some of the product can be lost on separation, or unexpected side reactions between reactants.

What is the percentage yield?

Actual yield as a proportion of theoretical yield.

How is percentage yield calculated?

(Actual yield / Theoretical yield) × 100.

What is atom economy?

Measure of how many atoms of the reactants end up as useful products.

Why is a high atom economy desirable?

It results in less waste and is more sustainable.

How is percentage atom economy calculated?

(M of useful product / M of all products) × 100.

How can concentration in mol/dm³ be calculated?

Moles of solute / volume (dm³).

What is a titration?

Method used to calculate the concentration of an unknown solution.

What is the end-point?

The point at which the reaction is complete (when the indicator changes color) and no substance is in excess.

How should solution be added from the burette close to the end point?

Drop by drop, swirling in between to see the color change better.

What is a titre?

Volume of solution added from the burette.

What are concordant titres?

Titres within 0.1 cm³ of each other.

What volume does one mole of any gas occupy at room temperature and pressure?

24 dm³ or 24,000 cm³.

What is an atom?

Smallest part of an element that can exist.

What is Dalton's model of the atom?

Atoms as solid spheres that could not be divided into smaller parts.

What is the plum pudding model of the atom?

Sphere of positive charge with negative electrons embedded in it.

What did scientists discover in the alpha scattering experiment?

Some alpha particles were deflected by the gold foil, showing that an atom's mass and positive charge must be concentrated in one small space (the nucleus).

Describe the nuclear model of the atom.

Dense nucleus with electrons orbiting it.

What did Niels Bohr discover?

Electrons orbit in fixed energy levels (shells).

What did James Chadwick discover?

Uncharged particle called the neutron.

Where are protons and neutrons located?

In the nucleus.

What is the relative mass of each sub-atomic particle?

Proton: 1, Neutron: 1, Electron: 0 (very small).

What is the relative charge of each sub-atomic particle?

Proton: +1, Neutron: 0, Electron: -1.

How can you find out the number of protons in an atom?

The atomic number on the Periodic Table.

How can you calculate the number of neutrons in an atom?

Mass number - atomic number.

Why do atoms have no overall charge?

Equal numbers of positive protons and negative electrons.

How many electrons would you place in the first, second, and third shells?

Up to 2 in the first shell and up to 8 in the second and third shells.

What is an element?

Substance made of one type of atom.

What is a compound?

Substance made of more than one type of atom chemically joined together.

What is a mixture?

Two or more substances not chemically combined.

What are isotopes?

Atoms of the same element (same number of protons) with different numbers of neutrons.

What are the four physical processes that can be used to separate mixtures?

Filtration, crystallisation, distillation, fractional distillation, chromatography.

What is relative mass?

The average mass of all the atoms of an element.

How are covalent bonds formed?

By atoms sharing electrons.

Which type of atoms form covalent bonds between them?

Non-metals.

Describe the structure and bonding of a giant covalent substance.

Billions of atoms bonded together by strong covalent bonds.

Describe the structure and bonding of small molecules.

Small numbers of atoms group together into molecules with strong covalent bonds between the atoms and weak intermolecular forces between the molecules.

Describe the structure and bonding of polymers.

Many identical molecules joined together by strong covalent bonds in a long chain, with weak intermolecular forces between the chains.

Why do giant covalent substances have high melting points?

It takes a lot of energy to break the strong covalent bonds between the atoms.

Why do small molecules have low melting points?

Only a small amount of energy is needed to break the weak intermolecular forces.

Why do large molecules have higher melting and boiling points than small molecules?

The intermolecular forces are stronger in large molecules.

Why do most covalent substances not conduct electricity?

Do not have delocalised electrons or ions.

Describe the structure and bonding in graphite.

Each carbon atom is bonded to three others in hexagonal rings arranged in layers - it has delocalised electrons and weak forces between the layers.

Why can graphite conduct electricity?

The delocalised electrons can move through the graphite.

Explain why graphite is soft.

Layers are not bonded so can slide over each other.

What is graphene?

One layer of graphite.

Give two properties of graphene.

Strong, conducts electricity.

What is a fullerene?

Hollow cage of carbon atoms arranged as a sphere or a tube.

What is a nanotube?

Hollow cylinder of carbon atoms.

Give two properties of nanotubes.

High tensile strength, conduct electricity.

Give three uses of fullerenes.

Lubricants, drug delivery (spheres), high-tech electronics.

What is an ion?

Atom that has lost or gained electrons.

Which kinds of elements form ionic bonds?

Metals and non-metals.

What charges do ions from Groups 1 and 2 form?

Group 1 forms 1+, Group 2 forms 2+.

What charges do ions from Groups 6 and 7 form?

Group 6 forms 2-, Group 7 forms 1-.

Name the force that holds oppositely charged ions together.

Electrostatic force of attraction.

Describe the structure of a giant ionic lattice.

Regular structure of alternating positive and negative ions, held together by the electrostatic force of attraction.

Why do ionic substances have high melting points?

Electrostatic force of attraction between positive and negative ions is strong and requires lots of energy to break.

Why don't ionic substances conduct electricity when solid?

Ions are fixed in position so cannot move, and there are no delocalised electrons.

When can ionic substances conduct electricity?

When melted or dissolved.

Why do ionic substances conduct electricity when melted or dissolved?

Ions are free to move and carry charge.

Describe the structure of a pure metal.

Layers of positive metal ions surrounded by delocalised electrons.

Describe the bonding in a pure metal.

Strong electrostatic forces of attraction between metal ions and delocalised electrons.

What are four properties of pure metals?

Malleable, high melting/boiling points, good conductors of electricity, good conductors of thermal energy.

Explain why pure metals are malleable.

Layers can slide over each other easily.

Explain why metals have high melting and boiling points.

Electrostatic force of attraction between positive metal ions and delocalised electrons is strong and requires a lot of energy to break.

Why are metals good conductors of electricity and thermal energy?

Delocalised electrons are free to move through the metal.

What is an alloy?

Mixture of a metal with atoms of another element.

Explain why alloys are harder than pure metals.

Different sized atoms disturb the layers, preventing them from sliding over each other.

What is a pure substance?

A pure substance is something made of only one type of substance.

What is the difference between the melting and boiling points of a pure and impure substance?

A pure substance has sharp melting and boiling points at specific temperatures, while an impure substance has broad melting and boiling points that occur across a range of temperatures.

What is a formulation?

A formulation is a mixture designed for a specific purpose.

What are some examples of formulations?

Examples of formulations include fuels, cleaning agents, paints, medicines, alloys, fertilizers, and foods.

What is chromatography?

Chromatography is a process for separating colored mixtures.

How is R calculated in chromatography?

R is calculated as R = (distance moved by substance) / (distance moved by solvent).

What is the test for hydrogen?

The test for hydrogen is that a lit splint gives a squeaky pop sound.

What is the test for oxygen?

The test for oxygen is that it re-lights a glowing splint.

What is the test for carbon dioxide?

The test for carbon dioxide is that it turns limewater milky when bubbled through it.

What is the test for chlorine?

The test for chlorine is that it bleaches damp litmus paper.

What is the test for aluminium, calcium, and magnesium ions?

The test involves adding sodium hydroxide solution to the sample to observe precipitate formation.