IGCSE Combined Science Chemistry (Chapter 1- 4)

Salt, sand and water are stirred together in a beaker. The salt dissolves in the water. What does the beaker contain?

• a mixture of solution and a solid

• a mixture of three elements

• only one compound and one solid

• only one compound containing three elements

Which ion is formed from a metal?

• Cl^-

• H⁺

• Na⁺

• NH₄⁺

Sodium burns in oxygen forming sodium oxide. An equation for this reaction is shown.

xNa + yO₂ → zNa₂O

What are x, y and z?

• x = 2, y = 1, z = 1

• x = 2, y = 2, z = 1

• x = 4, y = 1, z = 2

• x = 4, y = 2, z = 2

In which experiment is a compound formed?

• 
• 
• 
• 

A magnesium ion, Mg²⁺, is formed from a magnesium atom, Mg.

Which option about the numbers of protons and neutrons in the magnesium ion and in the magnesium atom is correct?

• Both Mg2+ and Mg have the same number of protons but different number of neutrons

• Both Mg2+ and Mg have different number of protons but same number of neutrons

• Both Mg2+ and Mg have the same number of protons and neutrons

Two different dyes are analysed using chromatography.

Each dye produces only one coloured spot on the chromatogram.

The Rf values of the coloured spots are shown.

The two different dyes are then mixed together to make a purple dye.

What is observed on the chromatogram of the purple dye?

• One spot with R_f value 0.3

• One spot with R_f value 0.6

• Two spots with R_f values 0.2 and 0.4

• Three spots with R_f values 0.2, 0.3 and o.4

Which statement describes a mixture?

• It contains molecules made from the same type of atom.

• It contains only one type of atom.

• It contains two different types of atom joined by chemical bonds.

• It contains two different types of atom that can be separated by physical processes.

Explain why a high temperature is needed to melt solid iron [2]

Write a balanced symbol equation for the complete combustion of pentane, C₅H₁₂, in oxygen. [2]

On the jamboard opened up by your instructor, draw a dot and cross diagram to show the bonding in a molecule of carbon dioxide, CO_2.

Show only the outer shell electrons. [2]