BECE (Ghana) Density and Mass — practice questions

1. Density is worked out as mass divided by volume. 2. The mass here is 240 grams and the volume is 60 millilitres. 3. Dividing gives 240 divided by 60, which equals 4. 4. So the density is 4 grams per millilitre. 5. Answering 3 would come from dividing 240 by 80, which is not the volume given. 6. Answering 6 would come from dividing 240 by 40, again not the volume given. 7. Answering 8 would come from doubling the correct result by mistake. _Source: Siyavula Natural Sciences Grade 8 (CC BY 4.0), Density tells us how 'tightly packed' a material is_

1. Heating gives the particles more energy so they move further apart. 2. The number of particles does not change, so the mass in grams stays the same. 3. The bar takes up more space, so its volume in millilitres goes up. 4. Density is mass divided by volume, so a larger volume with the same mass lowers it. 5. The density therefore becomes smaller when the bar is heated. 6. It cannot stay the same, because only one of the two quantities has changed. 7. It cannot reach zero, because the bar still has mass. _Source: Siyavula Natural Sciences Grade 8 (CC BY 4.0), Expansion and contraction of materials_