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A printable worksheet for the lesson Isotopes as fingerprints (GCSE). It prints on A4 without the website around it. The answers are on a separate sheet for the teacher.

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GCSE · Ages 14 to 16 (Years 10 and 11)Howardites worksheet

Isotopes as fingerprints

Name:Class:Date:

Key words

Isotope
One of two or more forms of the same chemical element whose atoms have different numbers of neutrons, and so different masses.
Meteorite
A meteorite is a piece of space rock that has survived its fall through the air and landed on Earth.
Parent body
The asteroid, moon or planet that a meteorite was originally part of before it was knocked off into space.
Mineral
A mineral is a natural solid with a fixed chemical recipe and an orderly inner arrangement of atoms.
Asteroid
A rocky or metal-rich object, smaller than a planet, that goes around the Sun.
Mass spectrometer
A mass spectrometer is an instrument that separates atoms or molecules by mass to measure isotopes and elements.

Choose the right answer

Circle the letter of the right answer.

  1. Why is the Aᵣ of oxygen so close to 16?
    • AOxygen-17 and oxygen-18 have no mass
    • BNearly all oxygen atoms are oxygen-16
    • CAᵣ always equals the lightest isotope
    • DOnly oxygen-16 has protons
  2. How many electrons does a neutral atom of oxygen-18 have?
    • A10
    • B18
    • C8
    • D16
  3. Which pair of atoms are isotopes of the same element?
    • A8p + 10n and 10p + 8n
    • B8p + 8n and 9p + 8n
    • C6p + 6n and 8p + 8n
    • D8p + 8n and 8p + 10n
  4. Why do meteorite oxygen isotopes need a mass spectrometer to measure?
    • AOxygen isotopes are too radioactive to handle
    • BThe differences are tiny, often parts per thousand or less
    • CEach isotope has different chemistry that hides it
    • DMeteorites contain almost no oxygen
  5. How many protons are in an atom of oxygen-17?
    • A9
    • B17
    • C8
    • D16

True or false?

Is the answer given right? Tick True or False.

  1. How many more neutrons does chlorine-37 have than chlorine-35?

    Answer given: 1 TrueFalse

  2. An element has isotopes of mass number 6 and 7, and its Aᵣ is 6.9. Which isotope is more common?

    Answer given: They are equally common TrueFalse

Write your answer

Answer in a word or a short sentence.

  1. What does a mass spectrometer do?
  2. Why is adding 16, 17 and 18 and dividing by 3 the wrong way to find Aᵣ for oxygen?
  3. A meteorite's oxygen matches Earth's almost exactly. Using the lesson, where could it have come from?

Task

Chlorine is about 75% chlorine-35 and 25% chlorine-37. Calculate its relative atomic mass. Then write three sentences explaining why two rocks with very different minerals can still be shown to come from the same asteroid.

Howardites · free to copy for use in your classroom · answers are on the separate teacher's answer sheet