Grade 8 Science: 10 Free Practice Questions

Answer: Protons and neutrons
The nucleus holds the protons and neutrons, which together account for nearly all the atom's mass. Electrons move in the space around the nucleus and are far lighter. Choosing protons and electrons mixes up the two charged particles - the proton is positive and sits in the nucleus, while the negative electron does not. Nucleus means heavy centre.

Answer: 5 chains
Follow the arrows from Plankton to Shark and list each complete path. Plankton, Small fish, Shark is one. Plankton, Small fish, Tuna, Shark is a second. Through Shrimp there are three more: Shrimp to Small fish to Shark, Shrimp to Small fish to Tuna to Shark, and Shrimp to Crab to Tuna to Shark. That makes five.

Answer: Kinetic to elastic, then electrical, then light
Your hand's motion winds a spring, storing elastic energy; the spring then drives a generator to make electricity, which the bulb turns into light, with heat lost at every step. There is no chemical store in a wind-up torch, which rules out two options, and no battery to charge.

Answer: Material Z
Material Z is the best sunshade because only 5 percent of the light is transmitted, the lowest in the table. A sunshade should stop light from passing through, whether by reflecting it or absorbing it. Material X reflects the most, but 20 percent still passes through. If you chose the highest reflector, you ignored what is transmitted. Compare the transmitted column to see what gets through.

Answer: Nuclear
The nuclear bar is the shortest, at 10 TWh. Solar and hydro each generated 20 TWh and wind generated 40 TWh. The least is found by looking for the shortest bar, not the lightest shading. Notice that nuclear power plants use uranium, which is nonrenewable, so the dark shading matches the key. Always check the scale before comparing bar heights.

Answer: Organisms with helpful inherited traits have more young
Natural selection works on variation that already exists in a population. Individuals whose inherited traits suit the environment survive and reproduce more, so those traits become more common in later generations. Organisms do not change because they need to, traits gained during life such as muscles are not inherited, and individuals do not evolve; populations do.

Answer: Letter Q
Letter Q marks a compression, a region where the particles are squeezed close together. Regions where the particles are spread far apart are rarefactions. In the figure Q sits over the tight cluster of lines, while the other letters sit over the wide gaps. Sound is a longitudinal wave, made of compressions and rarefactions. Look for where the particles bunch up.

Answer: Diagram B
In a lunar eclipse Earth is between the Sun and the Moon, so Earth's shadow falls on the Moon. Diagram B has Earth in the middle. Diagram D has the Moon in the middle, which is the arrangement for a solar eclipse. Diagrams A and C have the Sun between the other two bodies, so no eclipse is possible. A lunar eclipse happens only at full moon.

Answer: Gamma rays, ultraviolet, infrared, radio waves
The correct list is gamma rays, ultraviolet, infrared, radio waves. Gamma rays have the shortest wavelength, and wavelength gets longer through ultraviolet and infrared until radio waves, which are the longest. The first distractor lists them from longest to shortest, so it is the reverse. Remember that high frequency pairs with short wavelength, so the highest-energy waves come first.

Answer: C uses most per person, but B uses most in total
Total use equals people times energy per person. Country A: 50 x 100 = 5000. Country B: 200 x 40 = 8000. Country C: 20 x 300 = 6000, million GJ. Country C has the highest per-person use at 300 GJ, but Country B has the highest total because its population is largest. Per-person and total values answer different questions, so check which one a statement makes.