Howardites

A printable worksheet for the lesson Chondrites: the oldest rocks (Start here: Explorer). It prints on A4 without the website around it. The answers are on a separate sheet for the teacher.

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Start here: Explorer · Ages 10 and upHowardites worksheet

Chondrites: the oldest rocks

Name:Class:Date:

Key words

Chondrite
A chondrite is a stony meteorite full of tiny round grains called chondrules, and almost unchanged since the Solar System formed.
Stony meteorite
A stony meteorite is one made mostly of rocky minerals, with little or no metal.
Parent body
The asteroid, moon or planet that a meteorite was originally part of before it was knocked off into space.
Chondrule
A chondrule is a tiny round grain, often smaller than a grain of rice, that formed as a melted droplet in space before the planets existed.
Mineral
A mineral is a natural solid with a fixed chemical recipe and an orderly inner arrangement of atoms.
Olivine
A green mineral that is very common in meteorites and makes the gem called peridot.

Choose the right answer

Circle the letter of the right answer.

  1. A cut slice of a carbonaceous chondrite shows irregular white patches. What are they most likely to be?
    • AIron-nickel metal
    • BTroilite grains
    • CChondrules
    • DCAIs
  2. Why are hydrogen and helium left out when chondrites are compared with the Sun?
    • AThey are gases that solid rock did not keep
    • BRocks contain far more of them than the Sun
    • CThey cannot be measured in the Sun
    • DThey are made inside meteorites
  3. How big are chondrules usually?
    • ARoughly the size of a football, about 20 cm
    • BFrom a fraction of a millimetre to a few millimetres
    • CFrom a few centimetres to about a metre across
    • DSo small they cannot be seen with any microscope
  4. What is troilite?
    • AA kind of chondrule
    • BA green silicate like olivine
    • CA white calcium mineral
    • DAn iron sulphide mineral
  5. How does the overall chemistry of chondrites compare with the Sun's?
    • AVery close, if gases like hydrogen and helium are left out
    • BJust the same as the rocks in Earth's continental crust
    • CCompletely different, sharing almost no elements with it
    • DExactly the same, including all of its hydrogen and helium

True or false?

Is the answer given right? Tick True or False.

  1. How much of a chondrite can chondrules make up?

    Answer given: Always exactly a quarter TrueFalse

  2. Why are CAI minerals expected to be the first solids to form as hot gas cools?

    Answer given: They were made inside other stars and arrived later TrueFalse

Write your answer

Answer in a word or a short sentence.

  1. How can a grain inside a chondrite be older than the Sun?
  2. A grain formed "1 million years after time zero". What does that mean?
  3. In the fruit cake model of a chondrite, which part stands for the matrix?

Task

Look closely at a slice of fruit cake or a chocolate chip cookie. Draw it and label the parts: the round fruits or chips are like chondrules, the odd-shaped pieces are like CAIs, and the cake around them is like matrix.

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