Page 161 - Knowledge Organiser Yr8 24-25

Knowledge Base: Science 8.15 Mechanics Year 8
4. Liquid Pressure
4.1
How does liquid pressure change with increasing depth?
Liquid pressure increases the deeper you go
4.2
Why does liquid pressure change with increasing depth?
Liquid pressure increases with increasing depth because the weight of liquid above increases
4.3
Why does the jet from the bottom of this bucket travel further sideways?
The water at the bottom of the bucket is at the highest pressure and therefore is forced out of the hole more
4.4
What is upthrust?
The pressure that liquids (and gases) exert on the surface of an object
4.5
How and why does the force of upthrust change as an object sinks?
As an object sinks, the liquid pressure increases, which means the force of upthrust increases
4.6
Why do some objects float?
When the force of upthrust exerted by the liquid is equal and opposite to the object’s weight
4.7
Why do some objects sink?
If the object’s weight is greater than the force of upthrust exerted by the liquid
5. Convection
5.1
What is a fluid?
A substance which can flow (liquids and gases)
5.2
What is convection?
A heating transfer of energy that occurs in fluids
5.3
When fluids are heated, why do they take up more space?
The particles gain more energy and move more, taking up more space
5.4
When fluids are heated, what happens to their density?
Their density decrease because the particles are now occupying more space
5.5
What will happen to fluids that have a lower density than the fluid they are surrounded by?
They rise to the top
5.6
What will happen to fluids that have a higher density than the fluid they are surrounded by?
They will fall to the bottom
5.7
What is a convection current?
The process of fluids rising and falling due to differences in density
5.8
Why does heating air in a hot air balloon cause it to rise?
Air is a fluid. When it is heated it’s density decreases. This causes the air in the balloon to rise above the surrounding air.
5.9
Draw arrows to show the direction of fluid movement in this pan of water which is heated
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