GCSE Combined Science Chemistry — Questions and Answers
Question 1: What is the relative charge of a proton?
- +1 (Correct answer)
- -1
- 0
- +2
Correct answer: +1
A proton has a relative charge of +1 and a relative mass of 1. Protons are found in the nucleus of an atom alongside neutrons (which have no charge). The number of protons defines the element (atomic number).
Question 2: Which of the following substances has a giant covalent structure?
- Sodium chloride
- Diamond (Correct answer)
- Methane
- Magnesium oxide
Correct answer: Diamond
Diamond has a giant covalent structure where each carbon atom is bonded to four others in a tetrahedral arrangement. This creates a very strong, rigid lattice, which is why diamond is extremely hard and has a very high melting point.
Question 3: What is produced when a metal reacts with an acid?
- Metal oxide + water
- Salt + water
- Salt + hydrogen (Correct answer)
- Metal hydroxide + water
Correct answer: Salt + hydrogen
When a metal reacts with an acid, a salt and hydrogen gas are produced. For example: magnesium + hydrochloric acid → magnesium chloride + hydrogen. This is a key reaction type for GCSE Chemistry.
Question 4: In the periodic table, what name is given to the elements in Group 7?
- Alkali metals
- Noble gases
- Halogens (Correct answer)
- Transition metals
Correct answer: Halogens
Group 7 elements are called halogens. They include fluorine, chlorine, bromine, iodine, and astatine. Halogens are reactive non-metals that form salts when they react with metals — the name 'halogen' means 'salt-former'.
Question 5: What happens to the mass of a substance when it is burned in an open container?
- The mass always decreases
- The mass always stays the same
- The mass may appear to decrease because gaseous products escape (Correct answer)
- The mass doubles
Correct answer: The mass may appear to decrease because gaseous products escape
In an open container, gaseous products (like carbon dioxide and water vapour) escape into the air, so the measured mass appears to decrease. In a closed system, the total mass would remain the same, as stated by the law of conservation of mass.
Question 6: What type of bonding is found in a molecule of water (H₂O)?
- Ionic bonding
- Covalent bonding (Correct answer)
- Metallic bonding
- Hydrogen bonding
Correct answer: Covalent bonding
Water has covalent bonding — the hydrogen and oxygen atoms share pairs of electrons. Covalent bonds form between non-metal atoms. Each hydrogen atom shares one electron with oxygen, forming two single covalent bonds.
GCSE Combined Science Chemistry
What is the relative charge of a proton?