Final challenge: materials and forces

Las preguntas de esta práctica

Puedes leerlas antes de empezar, hacerlas en un papel o repasarlas después. Cada una tiene su solución explicada.

1. 1 · Properties

   Match each material with its property

   Use the opposite words.

   1. Glass
   2. Rubber
   3. Salt
   4. Talc

   • a) Flexible and elastic
   • b) Fragile
   • c) Soft
   • d) Soluble
   Ver la solución

   Respuesta: Glass → Fragile · Rubber → Flexible and elastic · Salt → Soluble · Talc → Soft

   Glass breaks easily, rubber bends and stretches, salt dissolves and talc is easy to scratch.

2. 2 · Properties

   What is the hardest natural material on Earth?

   It is used in jewellery.

   • a) Talc
   • b) Diamond
   • c) Wood
   • d) Glass
   Ver la solución

   Respuesta: b) Diamond

   Diamond is the hardest naturally occurring material.

3. 3 · Conduction

   A material that does not let heat travel through it easily is…

   Like the wooden handle of a pan.

   • a) a conductor
   • b) an insulator
   • c) elastic
   • d) soluble
   Ver la solución

   Respuesta: b) an insulator

   Insulators, like wood or plastic, don't let heat or electricity pass easily.

4. 4 · Properties

   What is the difference between flexible and elastic?

   Think of a wooden ruler and a rubber band.

   • a) Flexible = easy to bend; elastic = stretches and goes back to its shape
   • b) They mean the same
   • c) Flexible = easy to break; elastic = hard
   • d) Flexible = dissolves; elastic = doesn't dissolve
   Ver la solución

   Respuesta: a) Flexible = easy to bend; elastic = stretches and goes back to its shape

   A flexible material bends easily; an elastic one stretches and returns to its original shape.

5. 5 · Forces

   What can a force do?

   Choose the complete answer.

   • a) Only move objects
   • b) Move objects, stop them and change their shape
   • c) Only change colour
   • d) Nothing, forces are invisible
   Ver la solución

   Respuesta: b) Move objects, stop them and change their shape

   Forces can move or stop objects and change their shape.

6. 6 · Contact forces

   Which force slows down or stops moving things?

   It acts when surfaces rub together.

   • a) Gravity
   • b) Magnetism
   • c) Friction
   • d) Inertia
   Ver la solución

   Respuesta: c) Friction

   Friction slows down and stops moving objects.

7. 7 · Match

   Match each action with the force

   Contact or non-contact?

   1. Pushing a trolley
   2. Opening a drawer
   3. A leaf falling
   4. A magnet picking up pins

   • a) Gravity (non-contact)
   • b) Magnetism (non-contact)
   • c) Pull (contact)
   • d) Push (contact)
   Ver la solución

   Respuesta: Pushing a trolley → Push (contact) · Opening a drawer → Pull (contact) · A leaf falling → Gravity (non-contact) · A magnet picking up pins → Magnetism (non-contact)

   Push and pull need contact; gravity and magnetism act without touching.

8. 8 · Gravity

   Why is gravity weaker on the Moon than on Earth?

   More mass, more gravity.

   • a) Because the Moon has less mass
   • b) Because the Moon is hotter
   • c) Because there is no light
   • d) Because the Moon is a magnet
   Ver la solución

   Respuesta: a) Because the Moon has less mass

   The more mass something has, the stronger its gravity. The Moon has less mass than the Earth.

9. 9 · Gravity

   What keeps satellites and space stations in orbit around the Earth?

   An invisible force.

   • a) Friction
   • b) The Earth's gravity
   • c) Magnetism
   • d) The wind
   Ver la solución

   Respuesta: b) The Earth's gravity

   The Earth's gravity keeps the Moon, satellites and space stations in orbit.

10. 10 · Magnetism

    Which metals do magnets attract?

    Three metals.

    • a) Iron, nickel and cobalt
    • b) Gold, silver and copper
    • c) Aluminium and glass
    • d) All metals
    Ver la solución

    Respuesta: a) Iron, nickel and cobalt

    Magnets attract iron, nickel and cobalt, but not all metals.

11. 11 · Magnetism

    When do two magnets repel each other?

    Think about the poles.

    • a) When a north pole meets a south pole
    • b) When two north poles (or two south poles) meet
    • c) Never
    • d) Only in water
    Ver la solución

    Respuesta: b) When two north poles (or two south poles) meet

    The same poles repel; different poles attract.

12. 12 · The three Rs

    Keeping a glass jar to store your pencils is an example of…

    Using something again.

    • a) reducing
    • b) reusing
    • c) recycling
    • d) melting
    Ver la solución

    Respuesta: b) reusing

    Using something again for another job is reusing.

13. 13 · Science English

    The window has broken because glass is…

    Choose the property.

    • a) fragile
    • b) elastic
    • c) soluble
    • d) rigid
    Ver la solución

    Respuesta: a) fragile

    The window has broken because glass is fragile.

14. 14 · Science English

    The apple ___ off the tree because of the force of gravity.

    has + past participle

    • a) has fall
    • b) has fallen
    • c) have falling
    • d) is fall
    Ver la solución

    Respuesta: b) has fallen

    The apple has fallen off the tree because of gravity.