Combined Science Chemistry IGCSE

What is the atomic number of an element?

• The atomic number of an element is the number of neutrons in its nucleus.

• The atomic number of an element is the number of electrons in its nucleus.

• The atomic number of an element is the number of protons in its nucleus.

• The atomic number of an element is the number of isotopes it has.

Choose a suitable test to test the presence of hydrogen gas.

• Lighted splint test

• Glowing splint test

• Lime water test

• Bromine test

Explain the difference between an atom and an ion.

• An atom and an ion are the same thing.

• An atom is smaller than an ion.

• An atom has a charge, while an ion is neutral.

• An atom is neutral, while an ion has a positive or negative charge.

How do ionic bonds form?

• By sharing protons between atoms.

• By forming covalent bonds.

• By releasing neutrons during a reaction.

• By one atom transferring electrons to another atom.

What is the colour change of anhydrous copper (II) sulphate when added with water?

• Blue to pink

• Blue to white

• White to blue

• White to pink

Describe the process of neutralization.

• Neutralization is a chemical reaction between an acid and a base, resulting in the formation of water and a salt.

• Neutralization results in the formation of oxygen and carbon dioxide.

• Neutralization is a biological process involving plants and animals.

• Neutralization is a physical reaction between an acid and a base.

What is the difference between exothermic and endothermic reactions?

• Exothermic reactions occur in cold environments while endothermic reactions occur in hot environments

• Exothermic reactions absorb energy while endothermic reactions release energy

• Exothermic reactions release energy, usually in the form of heat, while endothermic reactions absorb energy from their surroundings.

• Exothermic reactions are slower than endothermic reactions

What is the role of catalysts in chemical reactions?

• Catalysts slow down reactions by increasing activation energy.

• Catalysts speed up reactions by lowering activation energy.

• Catalysts change the products of reactions.

• Catalysts have no effect on the speed of reactions.

Explain the concept of oxidation and reduction in electrolysis.

• Oxidation and reduction both happen at the same electrode.

• Oxidation occurs at the cathode and reduction at the anode.

• Electrons are gained at the anode and lost at the cathode.

• Oxidation happens at the anode, where electrons are lost, and reduction occurs at the cathode, where electrons are gained.

What are hydrocarbons?

• Synthetic materials used in construction.

• Minerals found in the ocean.

• Organic compounds consisting of hydrogen and carbon atoms.

• Inorganic compounds consisting of hydrogen and carbon atoms.