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Chapter 8 Practice Paper: Atoms and Molecules — mark scheme

QuizQuipPractice Series
QQ/S1SCI/CH8

Secondary 1 · Lower Secondary Science (G2 / G3)

Mark scheme

Atoms and Molecules

Chapter 8 Practice Paper · Maximum mark: 30

Notes for markers

  • Award one mark for each point marked [1], up to the marks shown for the part.
  • Accept answers worded differently that show the same understanding.
  • Units are required where the answer line shows one. ecf: allow an error carried forward.

Section A: Multiple-choice questions[10 marks]

QuestionAnswer
1AElectrons are negative. Protons are positive. Neutrons have no charge.1
2CProtons and neutrons are in the nucleus, and that is where almost all the mass is.1
3BA neutral atom has one electron for each proton. Atom Q has 17 electrons and atom P has 11, so Q has more.1
4DThe proton number identifies the element.1
5AThe formula shows one sulfur atom and two oxygen atoms, so each molecule contains three atoms.1
6CThe small 2 belongs to the oxygen symbol just before it.1
7DTwo oxygen atoms chemically combined make a molecule of the element oxygen.1
8BCarbon and hydrogen are chemically combined, and there is more than one element, so methane is a compound.1
9AA cheek cell contains a huge number of atoms, so one carbon atom is vastly smaller than the cell.1
10CNeutrons are in the nucleus and have no charge.1

Section B: Structured questions[20 marks]

QuestionAnswer and marking pointsMarks
1(a)

Positive, in the nucleus [1]

1
1(b)

Negative, around the nucleus [1]

1
1(c)

No charge.

  • No charge / neutral [1]
1
1(d)

There are equal numbers of positive protons and negative electrons, so the charges balance.

  • Equal numbers of protons and electrons [1]
  • The charges balance / cancel [1]
2
Total for Question 15
2(a)

There is 1 nitrogen atom. [1]

1
2(b)

There are 3 hydrogen atoms. [1]

1
2(c)

It is a compound. It contains two different elements, nitrogen and hydrogen, chemically combined.

  • Compound [1]
  • More than one element chemically combined [1]
2
2(d)

It contains two or more atoms chemically combined. [1]

1
Total for Question 25
3(a)

Yes, they are the same element.

  • Yes, the same element [1]
1
3(b)

They have the same number of protons.

  • Same proton number [1]
1
3(c)

There are 17 electrons. [1]

1
3(d)

The element is decided by the proton number. Neutrons affect the mass, not which element it is.

  • Proton number decides the element [1]
  • Neutrons do not decide the element [1]
2
Total for Question 35
4(a)

Carbon atom, cheek cell, sesame seed.

  • Atom, then cheek cell, then sesame seed [1]

A sesame seed is large enough to see and is much larger than a cheek cell. Both are far larger than an atom.

1
4(b)

An atom is far too small to see or to draw at its real size. A model shows the charges and where the particles are.

  • Too small to see / draw at real size [1]
  • The model shows charges or positions [1]
2
4(c)

The same knowledge can help people or harm them. Society has to decide how it should be used, not only learn the facts.

  • The knowledge can help and can harm [1]
  • A decision about use is a value question, not only a fact [1]
2
Total for Question 45

— End of mark scheme —