Section 5 - Solids, Liquids and Gases Flashcards
What is the equation for DENSITY?
Density = Mass / Volume
Describe an experiment to determine the density of an object
- Measure the mass of an object
- Measure the volume of an object. If the object is irregular, then put the object in water making sure it is fully submerged and measure the rise in water. If the object is regular, you can measure its sides to work out the volume
- Then use the formula to work out the density
what is the equation for PRESSURE?
Pressure = Force / Area
In which directions does pressure at a point in a gas or liquid (at rest) act on?
In all directions
What is the equation for PRESSURE DIFFERENCE (in liquids and gases)?
Pressure Difference = Height x Density x Gravitational Field Strength
What happens when a solid melts to form a liquid? *
Heat energy makes the particles vibrate faster until eventually the forces between them are overcome and the particles start to move around - this is melting
What happens when a liquid evaporates or boils to form a gas? *
The heat energy makes the particles move faster. Eventually, when they have enough energy, they will overcome their attraction to each other and big bubbles of gas form in the liquid - this is boiling.
If a particle is travelling in the right direction and they are travelling fast enough to overcome the attractive forces of the other particles, then they can escape when they are near the surface of the liquid. This is evaporation.
Describe the arrangement and motion of particles in solids*
They have strong forces of attraction which holds the particles close together in a fixed, regular arrangement.
They can only vibrate in their fixed positions as they don’t have much energy.
Describe the arrangement and motion of particles in liquids *
There are weaker forces of attraction so the particles are close together, but they can move past each other, and form irregular arrangements.
They have more energy, so they move in random directions at low speeds
Describe the arrangement and motion of particles in gases*
They have almost no forces of attraction between the particles and they have more energy so they are free to move and they travel in random directions at high speeds.
Describe the concept of Brownian Motion
Large, heavy particles (e.g. smoke) can be moved with Brownian motion by smaller, lighter particles (e.g. air) travelling at high speeds.
Why do molecules in a gas always put pressure on the walls of a container?
As they have a random motion and so they exert a force
Why is there an absolute zero of temperature?
Absolute zero (-273*C or 0 Kelvin) is the point at which atoms have as little kinetic energy as possible. Therefore, you can not get any colder.
What happens if you heat up particles (in terms of speed)?
They gain more energy, so there is an increase in the average speed of gas molecules
What is the temperature of a gas (in kelvins) proportional to? *
It is proportional to the average kinetic energy of its particles.
if you double its kelvin, then you double its kinetic energy
