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Science 8

Science 8 · Worksheets

Cumulative review

Ten questions of mixed difficulty, covering Cells and systems, Light and optical systems, Mechanical systems, Mix and flow of matter. Print it, or work through it on screen — the answer key starts on its own page.

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Science 8 · maddyhelps.com

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Circle the best answer for each question. Show your work in the space provided.

  1. Three gears sit in a row. Gear P turns clockwise and meshes with gear Q, and gear Q meshes with gear R. Which way does gear R turn?

    1. a) Clockwise only if R is larger than P
    2. b) Counterclockwise, opposite to gear P
    3. c) Either way, depending on the size of Q
    4. d) Clockwise, the same way as gear P

  2. A beam of white light passes through a glass prism and comes out as a band of colours, from red to violet. What does this show?

    1. a) The glass adds colour to the light as the light passes through
    2. b) Each colour reflects off a different face of the prism
    3. c) The prism absorbs white light and gives off coloured light
    4. d) White light is a mix of colours, each bent differently

  3. Muddy pond water looks cloudy when it is stirred. Left in a jar overnight, it clears as a layer of silt settles to the bottom. The muddy water was

    1. a) a solution
    2. b) a suspension
    3. c) a pure substance
    4. d) a saturated solution

  4. You step out of a dark movie theatre into bright sunlight, and your pupils shrink. Which part of the eye makes them smaller?

    1. a) The iris
    2. b) The retina
    3. c) The cornea
    4. d) The lens

  5. A pinhole camera is a box with a tiny hole in one end and a paper screen at the other. The image of a tree on the screen is upside down. Why?

    1. a) Rays travel straight, so light from the treetop lands at the bottom
    2. b) Light reflects off the inside walls of the box before reaching the screen
    3. c) The whole image squeezes through the hole and turns over on the way
    4. d) The pinhole acts like a lens, bending the light so that the image flips

  6. Many vaccines contain a weakened or killed germ, or a harmless piece of one. How does a vaccine protect a person from the real disease?

    1. a) It trains the immune system to recognize and destroy the germ
    2. b) It kills any of the germ already in the body, as an antibiotic does
    3. c) It makes the body's cells impossible for any germ to infect
    4. d) It coats the airways so the germ can never get into the body

  7. A clear, colourless liquid looks exactly like water. A student heats 50 mL of it in a dish until all the liquid is gone, and a thin white crust is left behind. The liquid was

    1. a) pure water that turned into a white solid
    2. b) a suspension with solid particles in it
    3. c) a pure substance, since it looked like one
    4. d) a solution with a solid dissolved in it

  8. A student dissolves 12 g of salt in water to make 200 mL of solution. What is the concentration in grams per 100 mL?

    1. a) 0.06 g per 100 mL
    2. b) 12 g per 100 mL
    3. c) 24 g per 100 mL
    4. d) 6 g per 100 mL

  9. A ray of light hits a flat mirror, making an angle of 25° with the mirror's surface. What is the angle of reflection?

    1. a) 50°
    2. b) 65°
    3. c) 25°
    4. d) 130°

  10. Liam can read his phone clearly, but the words on the board at the front of the class are blurry. Which describes his vision and the lenses that correct it?

    1. a) Nearsighted; convex lenses that bring light together
    2. b) Nearsighted; concave lenses that spread light out
    3. c) Farsighted; concave lenses that spread light out
    4. d) Farsighted; convex lenses that bring light together

Answer key · Cumulative review

Science 8 · maddyhelps.com

  1. d) Clockwise, the same way as gear P — Two meshing gears always turn in opposite directions, so Q turns counterclockwise, and R, meshing with Q, turns clockwise again. Size changes how fast a gear turns, never which way; a middle gear used like Q is called an idler gear.
  2. d) White light is a mix of colours, each bent differently — Each colour slows by a slightly different amount in glass, so each bends by a different amount and the colours fan out, violet bending most and red least. The prism adds nothing: a second prism turned the other way can combine the colours back into white light.
  3. b) a suspension — In a suspension, solid particles are spread through a liquid but are big enough to settle out when it stands, and a filter can catch them. The dissolved particles in a solution never settle, however long it stands, so water that clears overnight was never a solution.
  4. a) The iris — The pupil is just an opening; the iris is the coloured ring of muscle around it, which narrows the pupil in bright light and widens it in dim light, as a camera's aperture does. The lens focuses the light, and the retina detects it.
  5. a) Rays travel straight, so light from the treetop lands at the bottom — Light from the top of the tree travels in a straight line down through the hole and lands at the bottom of the screen, while light from the bottom lands at the top, so the image is flipped. A pinhole has no glass and bends nothing; the image is built point by point from straight rays, not carried through the hole as a whole picture.
  6. a) It trains the immune system to recognize and destroy the germ — The immune system learns to recognize the germ from the vaccine without the person falling ill, and remembers it, so if the real germ arrives it is destroyed before it can cause disease. A vaccine prevents an infection rather than curing one; killing bacteria already in the body is what antibiotics do.
  7. d) a solution with a solid dissolved in it — A solution looks like a single substance because the solute's particles are spread evenly among the water particles, too small to see, and evaporating the water leaves the solute behind. Pure water leaves nothing when it evaporates, and a suspension would have looked cloudy.
  8. d) 6 g per 100 mL — 200 mL is two lots of 100 mL, so each 100 mL holds 12 ÷ 2 = 6 g of the salt, which is the solute. Answering 12 g forgets that the salt is spread through 200 mL, not 100 mL, and 24 g doubles where it should halve.
  9. b) 65° — The law of reflection measures angles from the normal, not from the mirror, so the angle of incidence is 90° − 25° = 65°, and the angle of reflection equals it. 25° is the angle to the surface, the usual trap, and 130° is the whole angle between the incoming and reflected rays.
  10. b) Nearsighted; concave lenses that spread light out — Nearsighted people see near things clearly, and distant things blur because the eye brings their light to a focus in front of the retina. A concave lens spreads the rays a little before they enter the eye, moving the focus back onto the retina; the name trips people up, because it describes what you see well, not what is blurry.