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# Matter

### Third form matter facts

What are the units for mass? kilogrammes (or grammes)
What are the units for weight? Newtons (N)
On Earth what (approximately) is the weight of 1 kg? 10 Newtons
If my mass on Earth is 50 kg, what is my mass on the Moon where gravity is 1/6 of its value on the Earth? Mass never changes, 50 kg.
If my weight on Earth is 600 N, what is my weight on the Moon where gravity is 1/6 of its value on the Earth? 600/6 = 100 N
What is the effect called when you look through a microscope at smoky air and see bright spots moving randomly? Brownian Motion
In Brownian motion, when you look through a microscope and see bright spots moving randomly, what are the spots? Smoke particles (Brown may have looked at pollen grains)
When you look through a microscope at smoky air and see bright spots moving randomly, what causes the movement? Air molecules bumping into the smoke.
What is diffusion? When something spreads from an area of high concentration into an area of low concentration.
Gas molecules move at about 300 m/s. Why does it take a long time for gas to diffuse across a room? The gas molecules bump into air molecules and keep changing direction.
What do we call a space with no air? A vacuum.
What are the units for pressure? Pascals (Pa) = Newtons per metre squared
Which is it? Force = pressure over area or Pressure = force over area? Pressure = force divided by area.
A 600 N woman in stiletto heels puts all her weight on one heel (area 2 cm squared) and treads on my foot. Find the pressure. pressure = 600/2 = 300 N/cm2
A bag has a string handle, area 0.5 cm squared on my hand. Weight of bag + food = 30 N. What is pressure? pressure = 30/0.5 = 60 N/cm squared
A brick is lying on its side. Will the pressure be bigger or smaller if it is turned onto its end? (end has a smaller area). Pressure = force/area. Divide by smaller area, get a LARGER answer.
Why does an animal with a long neck need high blood pressure? Pressure increases with depth (height) in a liquid. Need high pressure from heart to pump blood to brain.
Pressure throughout liquid at same depth is the same, why are hydraulic brakes force multipliers? Area of pistons at brakes is much greater than area of piston behind brake pedal.
Why is air pressure on top of a mountain less than at sea level? Depth (height) of air above you is greater at sea level.
How do gases put pressure on things? Gas particles (molecules) move fast in all directions and collide with container walls.
Why does a solid expand when heated? Particles move faster and further apart when substance is heated.
Why are most liquids less dense than solids? Particles are not packed so neatly, not so many in the same volume.
Why are gases less dense than liquids or solids? Particles are spread far apart, lots of empty space in between.
Which expands most for the same change in temperature, solid, liquid or gas? Gases expand most for same change in temperature.
Give three words for liquid turning to gas. Evaporation, boiling or vaporisation.
Why does a bi-metallic strip bend when it is heated? One of the two metals it is made of expands more than the other one. It goes on the outside of the curve.
Name one use for a bi-metallic strip. Something that turns off the electric current at a certain temperature, e.g. in an electric iron.
What are the units of density? kg per metre cubed, or grammes per cm cubed.
A 12 kg block of wood has a volume of 3 metres cubed. What is its density? 12/3 = 4 kg per metre cubed.
A 54 kg woman has a volume of 60 metres cubed. what is her density? 54/60 = 0.9 kg per metre cubed.
Iron has a density of 8 grammes per cm cubed. What is the mass of 2 cm cubed of iron? 2 x 8 = 16 grammes
density = mass divided by what? density = mass divided by VOLUME.
mass = density TIMES or DIVIDED by volume? mass = density times volume.
A measuring cylinder contains 20 cm3 of water. A stone is dropped in and the level rises to 25 cm3. What is the volume of the stone? 25 - 20 = 5 cm3
Created by: waslancing