Physics - 0625 CIE

Density

Gbogbo ọrọ náà

Lead is called heavy and cork is called light, yet a tiny lead pellet weighs far less than a whole cork life-ring. What we really mean is that lead packs much more mass into each unit of volume. That idea, mass per unit volume, is density, and it lets you predict whether a pebble sinks, why an iron ship floats, and which liquid settles on top when two will not mix.

In this lesson you will define density, learn the equation that links mass, volume and density, and measure it for a liquid, a regular solid and an awkward irregular solid using displacement. You will then use density data the way examiners ask: to decide whether an object floats or sinks, and whether one liquid floats on another.

Ebumnobi

Define density as mass per unit volume; recall and use the equation m ρ = V
Describe how to determine the density of a liquid, of a regularly shaped solid and of an irregularly shaped solid which sinks in a liquid (volume by displacement), including appropriate calculations
Determine whether an object floats based on density data
[Supplement] Determine whether one liquid will float on another liquid based on density data given that the liquids do not mix

Akọmọ Ojú-ẹkọ

Engineers work out the weight of a bridge from the volumes and densities of its materials before a single beam is cut. A diver chooses weights so their average density matches the water. A cook knows oil floats on vinegar. All of these are density at work, and in the exam density is one of the most reliable sources of marks because the equation is short and the reasoning about floating is logical, not memorised.

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Ayẹwo Ẹkọ

Ekele diri gi maka imecha ihe karịrị na Density. Ugbu a na ị na-enyochakwa isi echiche na echiche ndị dị mkpa, ọ bụ oge iji nwalee ihe ị ma. Ngwa a na-enye ụdị ajụjụ ọmụmụ dị iche iche emebere iji kwado nghọta gị wee nyere gị aka ịmata otú ị ghọtara ihe ndị a kụziri.

Ị ga-ahụ ngwakọta nke ụdị ajụjụ dị iche iche, gụnyere ajụjụ chọrọ ịhọrọ otu n’ime ọtụtụ azịza, ajụjụ chọrọ mkpirisi azịza, na ajụjụ ede ede. A na-arụpụta ajụjụ ọ bụla nke ọma iji nwalee akụkụ dị iche iche nke ihe ọmụma gị na nkà nke ịtụgharị uche.

Jiri akụkụ a nke nyocha ka ohere iji kụziere ihe ị matara banyere isiokwu ahụ ma chọpụta ebe ọ bụla ị nwere ike ịchọ ọmụmụ ihe ọzọ. Ekwela ka nsogbu ọ bụla ị na-eche ihu mee ka ị daa mba; kama, lee ha anya dị ka ohere maka ịzụlite onwe gị na imeziwanye.

Density is defined as A. mass times volume B. mass divided by volume C. volume divided by mass D. weight divided by area Answer: B
A block has mass 240 g and volume 30 cm3. Its density is A. 0.125 g/cm3 B. 8 g/cm3 C. 80 g/cm3 D. 7200 g/cm3 Answer: B
A stone of mass 75 g raises the water in a measuring cylinder from 40 cm3 to 65 cm3. Its density is A. 1.15 g/cm3 B. 3.0 g/cm3 C. 1.88 g/cm3 D. 25 g/cm3 Answer: B
An object will float in a liquid if the object's density is A. greater than the liquid's density B. equal to its own weight C. less than the liquid's density D. equal to the liquid's mass Answer: C
The density of water is 1.0 g/cm3. In kg/m3 this is A. 0.001 B. 1 C. 100 D. 1000 Answer: D