Grade 8 · Science

Grade 8 science

Grade 8 science gets more precise: measuring density, looking inside cells, explaining why a ship floats and a pebble sinks. Here is what it covers, where kids usually get stuck, and one way to help.

What your child learns this year

Topics differ by province and state, but most grade 8 classes cover several of these:

  • Cells. Plant and animal cells, their parts, and how cells make up tissues and organs.
  • Fluids. Density, buoyancy, viscosity and pressure, and how fluids are used in machines.
  • Systems. How the parts of a system, natural or built, work together.
  • Water on Earth. Oceans, watersheds, glaciers, and how water shapes climate and land.
  • Doing science. Measuring mass and volume carefully, and calculating with the results.

In the US, states that follow the Next Generation Science Standards teach grades 6 to 8 as one band, so grade 8 topics vary from school to school.

Where kids usually get stuck

  1. 1Dividing the wrong way. Density is mass ÷ volume. Doing volume ÷ mass flips the answer, and the float-or-sink prediction with it.
  2. 2Thinking only animal cells have mitochondria. Plant cells have them too. Plants also have chloroplasts and a cell wall, which animal cells don't.
  3. 3Thinking a thicker liquid is always heavier. Thickness (viscosity) and density are different: oil is thicker than water but floats on it.

One of Pip's tricks

Density decides floating

Use it when predicting whether an object or a liquid will float or sink when you know its mass and volume.

  1. Find the density: mass ÷ volume, in g/mL or g/cm³.
  2. Compare it with the density of the fluid. Water is 1 g/mL, the same as 1 g/cm³.
  3. Less dense than the fluid, it floats; more dense, it sinks.

Watch it work. A block has a mass of 30 g and a volume of 40 cm³. Its density is 30 ÷ 40 = 0.75 g/cm³. That is less than water's 1 g/cm³, so the block floats.

Why it works: density is the mass packed into each cubic centimetre, so an object less dense than the fluid weighs less than the same volume of that fluid, and the fluid's upward push wins.

Try three

Tap a choice to see if it is right, with the reason.

  1. 1.A block has a mass of 60 g and a volume of 40 cm³. Will it float in water?

  2. 2.Oil (0.9 g/cm³) is poured into water (1 g/cm³). The oil…

  3. 3.Do plant cells have mitochondria?

How Sparkpip fits in

Pip, Sparkpip's tutor, works through questions like these with your child one small step at a time, using ways of thinking like the one above.

Start freeSee how it works

Your curriculum

Sparkpip is built on the grade 8 science curriculum for your province or state. The official pages:

Also: Grade 7 science · Grade 9 science · Grade 8 math · Grade 8 English