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Science 7

Science 7 · Worksheets

Year-end challenge

Ten questions of mixed difficulty, covering Heat and temperature, Interactions and ecosystems, Planet Earth, Plants for food and fibre, Structures and forces. Print it, or work through it on screen — the answer key starts on its own page.

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Year-end challenge

Science 7 · maddyhelps.com

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

  1. A bathtub holds water at 40 °C, and a mug holds water at 80 °C. Which statement is correct?

    1. a) The bathtub's particles move faster, because it holds more water
    2. b) Both hold the same thermal energy, because both are just water
    3. c) The mug's particles move faster, but the bathtub holds more thermal energy
    4. d) The mug holds more thermal energy, because its water is hotter

  2. In a meadow, grasses capture 10 000 kJ of energy from sunlight. Mice eat the grasses, snakes eat the mice, and hawks eat the snakes. If roughly 10% passes on at each step, about how much reaches the hawks?

    1. a) 100 kJ
    2. b) 1000 kJ
    3. c) 7290 kJ
    4. d) 10 kJ

  3. Students test paper bridges. The specification: hold the most pennies for each sheet of paper used. Bridge A used 6 sheets and held 120 pennies; bridge B used 3 sheets and held 80. Which met the specification better?

    1. a) Bridge B, at about 27 pennies per sheet
    2. b) Bridge A, because more paper makes it sturdier
    3. c) Bridge A, because it held 40 more pennies
    4. d) Neither, since both bridges collapsed in the end

  4. Which of these energy sources is renewable?

    1. a) Oil
    2. b) Coal
    3. c) Wind
    4. d) Natural gas

  5. Two mineral samples both look shiny and gold. Rubbed on an unglazed tile, one leaves a greenish-black streak and the other a golden-yellow streak. What is the best conclusion?

    1. a) They are different minerals, since streak is more reliable than colour
    2. b) They are different minerals, since one must be harder
    3. c) They are the same mineral, since they are the same colour
    4. d) They are the same mineral, but one sample is dirtier

  6. Sandstone is buried deep underground, where great heat and pressure change it into a much harder rock without melting it. The new rock is

    1. a) sedimentary
    2. b) metamorphic
    3. c) extrusive igneous
    4. d) intrusive igneous

  7. A town sprays a pesticide in its parks to kill mosquitoes. Which result is an unintended consequence?

    1. a) Families can use the parks more on summer evenings
    2. b) Fewer mosquitoes bite people who visit the parks
    3. c) The number of mosquitoes falls for several weeks
    4. d) Bats and dragonflies that eat mosquitoes have less food

  8. A student heats crushed ice and records the temperature every minute: −10, −5, 0, 0, 0, 0, 5, 10 °C. Why does the temperature stay at 0 °C for four readings?

    1. a) The energy is going into melting the ice, not warming it
    2. b) The burner gave out less energy while those readings were taken
    3. c) The ice gives off heat as it melts, cancelling the burner
    4. d) A thermometer cannot measure the temperature of melting ice

  9. Many First Nations and Métis families dried saskatoon berries to store and eat through the winter. Why does drying keep food from spoiling?

    1. a) The moulds and bacteria that spoil food need water to grow
    2. b) Dried berries are too hard for insects to bite into
    3. c) Heat from the sun kills every germ, so none can return
    4. d) Drying adds vitamins that stop the berries from rotting

  10. A plank is laid across a stream, and a hiker stands in the middle. The plank sags. Which describes the forces inside the plank?

    1. a) The whole plank is in tension, because it is being pulled downward
    2. b) The top is stretched (tension) and the bottom is squeezed (compression)
    3. c) The top is squeezed (compression) and the bottom is stretched (tension)
    4. d) The plank is in torsion, because bending is a kind of twisting

Answer key · Year-end challenge

Science 7 · maddyhelps.com

  1. c) The mug's particles move faster, but the bathtub holds more thermal energy — Temperature is the average motion of the particles, so the hotter mug wins on that. But the bathtub has vastly more particles, and adding up all of their energy gives far more in total, which is why a tub of warm water can melt far more snow than a mug of hot water.
  2. d) 10 kJ — Each step passes on roughly a tenth: 10 000 kJ in the grasses, 1000 kJ to the mice, 100 kJ to the snakes and 10 kJ to the hawks. Taking away 10% at each step gives 7290 kJ, but it is the other way round: about 90% is used for living or lost as heat at every level.
  3. a) Bridge B, at about 27 pennies per sheet — The specification asks for pennies per sheet, so divide: A held 120 ÷ 6 = 20 and B held 80 ÷ 3 ≈ 27. A held more pennies only because it used twice the paper, and both bridges were always going to collapse, since loading until failure is how the maximum load is found.
  4. c) Wind — A renewable source is replaced naturally as fast as we use it, and the wind keeps blowing because the Sun keeps heating the air unevenly. Coal, oil and natural gas formed from ancient living things over millions of years, so what we burn is gone for good on any time scale that matters to us.
  5. a) They are different minerals, since streak is more reliable than colour — Pyrite, known as fool's gold, looks like gold but leaves a greenish-black streak, while real gold leaves a golden-yellow one. The colour of a sample's surface can vary or fool you, but a mineral's streak, the colour of its powder, stays the same.
  6. b) metamorphic — Heat and pressure that change a rock without melting it make metamorphic rock; sandstone becomes quartzite. If the rock had melted and then cooled, the new rock would be igneous, and it cannot still be sedimentary once heat and pressure have changed it.
  7. d) Bats and dragonflies that eat mosquitoes have less food — The spraying was meant to cut mosquito numbers, so fewer mosquitoes and fewer bites are the intended results. An unintended consequence is a side effect nobody was aiming for, such as taking food away from the animals that eat mosquitoes.
  8. a) The energy is going into melting the ice, not warming it — While ice melts, the energy goes into freeing particles from their fixed places rather than making them move faster, so the temperature holds level until all the ice has melted. The burner is adding energy the whole time; a flat part on a heating graph means a change of state, not a pause in heating.
  9. a) The moulds and bacteria that spoil food need water to grow — Moulds and bacteria need water, so taking it out slows them almost to a stop, and dried food keeps for months. Drying does not sterilize food or add anything to it: germs still land on it, but without water they cannot grow.
  10. c) The top is squeezed (compression) and the bottom is stretched (tension) — When a beam bends, its top surface gets shorter and its bottom surface gets longer, so it is in compression on top and tension underneath. Concrete is weak in tension, which is why concrete beams have steel rods set near the bottom, where the pulling is.