P6 - Molecules and Matter

Density =

mass/volume

What objects float in water

Objects that have a lower density than water

How energetic are the particles in the three states of matter?

particles of a solid are the least energetic and are in fixed postion

Particles in a liquid move about randomly but are still in contact with each other. They are more energetic than particles in a solid

Particles in a gas move about randomly and are far from each other. They are the most energetic state of matter

Why does the mass of a substance stay the same if it changes state?

Its mass stays the same because the amount of particles stays the same

What is the definition of a boiling point and a melting point?

Melting point - temperature which it melts at (and soldifies) Boiling Point - temperature which it boils (and condenses)

When does evaporation occur?

Evaporations occur throughout from the surface of a liquid when its temperature is below its boiling point.

What part of a temperature time graph shows the melting and boiling point of a substance?

The flat section

What is internal energy?

The energy stored by the particles of a substance

What factor affects internal energy?

Temperature

What decides if a substance is a solid, liquid or gas?

The strength of the forces of attraction between the particles

What happens when a substance is heated?

If its temperature rises, the kinetic energy of its particles increases.

If it melts or boils, the potential energy of its particles increases

What is pressure of a gas by a surface caused by?

The particles of a gas repeatedly hitting a surface

What is latent heat?

Energy needed for a substance to change its state without changing its temperature.

What is specific latent heat of fusion?

The amount of energy needed to melt (or boil) 1kg of a substance without changing its temperature

Specific latent heat =

energy/mass

How can the specific latent heat of ice be measured?

It can be measure using a low-voltage heater to melt the ice (or to boil the water)

why does the pressure increase if the temperature increases in a sealed container

the pressure increases because the particles have more kinetic energy which leads to harder and more frequent collisions as the particles are moving faster

What is evidence of the random motion of gas molecules?

The unpredictable motion of smoke particles

For a fixed mass of a gas at constant temperature - what happens if its volume decreases?

The pressure increases

Why can the temperature increases if its compressed rapidly?

Work is being done on it and the energy isn't transferred quickly to its surroundings