The questions are on the periodic table test. Take it under real conditions before reading the mark scheme.
Quick answer: An element is a pure substance made of only one kind of atom, written with a symbol such as Na or Fe. This mark scheme gives the model answers and the marks for the 8 questions of the grade 8 science test on periodic table, from symbols to predict rubidium, with the equivalent answers to accept.
The model answers show what earns full marks. Look at the marking notes to see where marks are awarded, and notice that explanations need a reason as well as a statement.
Level: Grade 8 science (Year 9 · Class 8) · Curriculum: MS-PS1-1
Question 1 Symbols (3 marks)
(a) Na. (b) Fe. (c) K.
Marking: 1 mark each; the capital letter must be correct.
Question 2 Using the table (3 marks)
(a) Magnesium. (b) Ne and Ar. (c) Chlorine (Cl).
Marking: 1 mark each.
Question 3 Compound or mixture (2 marks)
In a mixture the iron and sulfur are not chemically joined, so each keeps its own properties and a magnet can remove the iron. In a compound, iron sulfide, they are chemically joined in a fixed ratio and the properties are new.
Marking: 1 mark for a mixture description, 1 mark for a compound description.
Question 4 Metals and non-metals (3 marks)
Metals are shiny and conduct electricity well; non-metals are dull and are usually poor conductors. Metals are malleable but solid non-metals are brittle.
Marking: 1 mark for each correct property of metals and 1 for each matching property of non-metals, maximum 3.
Question 5 Fixed ratio (3 marks)
(a) 15.0 ÷ 6.0 = 2.5 times as much, so 2.5 × 4.0 = 10.0 g of oxygen. (b) 15.0 + 10.0 = 25.0 g.
Marking: 1 mark for the scale factor, 1 for the oxygen mass, 1 for the oxide mass.
Question 6 Noble gases (2 marks)
Neon is a noble gas in group 18 and its atoms are very unreactive, so it does not react with oxygen or burn. It glows when electricity passes through the gas.
Marking: 1 mark for unreactive/group 18, 1 mark for not burning.
Question 7 Spot the mistake (2 marks)
Sodium and chlorine are chemically joined, so salt is a compound. A mixture is not chemically joined, and salt has properties unlike sodium or chlorine.
Marking: 1 mark for compound, 1 mark for the reason.
Question 8 Predict rubidium (2 marks)
Rubidium is a soft, shiny metal and, like the other alkali metals, it reacts quickly with water. Its reactivity is higher than potassium because reactivity increases down group 1.
Marking: 1 mark for two properties, 1 mark for the comparison.
