In which changes do the particles move further apart?

• W and X

• W and Z

• X and Y

• Y and Z

Which statement about the atoms of all the isotopes of carbon is correct?

• They are all radioactive.

• They have the same mass.

• They have the same number of neutrons.

• They have the same number of electrons in the outer shell.

Which diagram represents the structure of silicon(IV) oxide?

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Lithium and fluorine react to form lithium fluoride.

A student writes three statements about the reaction.

1 Lithium atoms lose an electron when they react.

2 Each fluoride ion has one more electron than a fluorine atom.

3 Lithium fluoride is a mixture of elements.

Which statements are correct?

• 1 and 2 only

• 1 and 3 only

• 2 and 3 only

• 1, 2 and 3

Which definition of isotopes is correct?

• atoms of the same element that have the same number of electrons and nucleons

• atoms of the same element that have the same number of neutrons and protons

• atoms of the same element that have the same number of protons but a different number of electrons

• atoms of the same element that have the same number of protons but a different number of nucleons

In which molecule are all the outer shell electrons from each atom used to form covalent bonds?

• CH₄

• Cl₂

• H₂O

• NH₃

A compound has the formula XF₂ and has a relative mass of 70.

What is element X?

• gallium

• germanium

• sulfur

• ytterbium

The diagram shows a section of an overhead power cable.

Which statement explains why a particular substance is used?

• Aluminium has a low density and is a good conductor of electricity.

• Ceramic is a good conductor of electricity.

• Steel can rust in damp air.

• Steel is more dense than aluminium.

Three substances are electrolysed using inert electrodes.

Which substances produce hydrogen at the negative electrode?

1 concentrated hydrochloric acid

2 concentrated aqueous sodium chloride

3 dilute sulfuric acid

• 1, 2 and 3

• 1 and 2 only

• 1 and 3 only

• 2 and 3 only

Which row describes an endothermic reaction?

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