Every card in Matter and particles, Year 8
The whole deck, in order — so you can read it through before your child ever sees it.
- Under a microscope, specks of smoke lit up in air are seen to do what?
Jitter about randomly
HintThey never keep still or keep to a straight path.
WhyEach speck shows as a bright dot that darts a tiny distance one way, then another, with no pattern. This is called Brownian motion.
- What does Brownian motion reveal about the air around a smoke speck?
It is made of moving particles too small to see
HintSomething invisible must be doing the pushing.
WhyThe specks cannot push themselves about. Their jittering was the first direct evidence that the air is made of fast-moving particles.
- Why is the movement of a smoke speck random, not steady in one direction?
The collisions come unevenly from all sides
HintNo two instants bring an identical set of knocks.
WhyAir particles hit the speck from every direction. By chance the hits never quite balance, and the imbalance keeps changing.
- A smoke cell is watched for an hour. Does the jittering of the specks ever stop?
No — the air particles never stop moving
HintAsk whether the cause has gone away.
WhyAs long as the air is at any ordinary temperature, its particles keep moving and keep colliding with the specks.
- A metal jar lid is stuck. Why does running hot water over it help?
The metal lid expands and loosens
HintThink about what heating does to the size of a solid.
WhyHeated particles vibrate more and push each other slightly further apart. The lid grows a little wider than the glass and loses its grip.
- When a solid expands on heating, do its particles get bigger?
No — they move further apart
HintA hot iron bar is longer, yet it has no extra atoms.
WhyThe particles vibrate more strongly and so take up more room each. The solid grows because the spacing grows.
- Why are small gaps left between the sections of a steel bridge?
To give the steel room to expand on hot days
HintThink about what a long strip of metal does on a hot day.
WhyA long bridge can grow by several centimetres between winter and summer. The gaps, called expansion joints, let it do so safely.
- Which has more mass: a kilogram of feathers or a kilogram of iron?
Neither — they have the same mass
HintRead the two amounts carefully.
WhyA kilogram is a kilogram. The feathers take up far more space because they are much less dense, but the two masses are equal.
- Two cubes are the same size. One is iron and one is wood. Why is the iron cube heavier?
Iron is denser: more mass is packed into the same space
HintCompare how much matter fits in each cubic centimetre.
WhyDensity compares mass with volume. In iron the particles are heavier and more closely packed, so each cubic centimetre has more mass.
- Why is a gas far less dense than the same substance as a solid?
Its particles are much further apart
HintThink about the amount of empty space there is.
WhyThe particles are identical in both states, but in the gas they are spread through a far larger volume, so each cubic centimetre holds very little mass.
1★ KS3-PHYS-MAT-0033
2★ KS3-PHYS-MAT-0034
3★ KS3-PHYS-MAT-0035
4★ KS3-PHYS-MAT-0036
5★ KS3-PHYS-MAT-0037
6★ KS3-PHYS-MAT-0038
7★ KS3-PHYS-MAT-0039
8★ KS3-PHYS-MAT-0040
9★ KS3-PHYS-MAT-0041
10★ KS3-PHYS-MAT-0042
Keep what you learn
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