P6

Question 1

What is equation for density?

Answer 1

density = mass / volume

Question 2

How do you find a solid or liquid objects density?

Answer 2

Measure it’s mass and it’s volume, then use the density equation p = m / V

Question 3

What happens to objects that have a lower density than water?

Answer 3

The float in water

Question 4

Particles in a solid

Answer 4

Cannot be compressed, all touch and are in fixed positions, vibrate about a fixed point
• Least energetic state of matter

Question 5

Particles in a liquid

Answer 5

Move about at random and are in contact with each other
• more energetic than a solid

Question 6

Particles in a gas

Answer 6

Far apart (so less dense than a liquid)
Move about randomly
Most energetic

Question 7

Mass when changing state

Answer 7

Mass remains the same when a substance changes state because the number of particles stays the same

Question 8

MP and BP in a pure substance

Answer 8

For a pure substance:
•its melting point is the
temperature at which it melts (which is the same temperature at which it solidifies)
• its boiling point is the temperature at which it boils (which is the same temperature at which it condenses).
• Energy is needed to melt a solid or to boil a liquid.
• Boiling occurs throughout a liquid at its boiling point. Evaporation occurs from the surface of a liquid when its temperature is below its boiling point.
• The flat section of a temperature-time graph gives the melting point or the boiling point of a substance.

Question 9

Internal energy

Answer 9

• Increasing the temperature of a
sunstanco increases ire infernal
energy.
• The strength of the forces of attraction between the particles
of a substance explains why it is a solid, a liquid, or a gas. when a substance is heated:
•if its temperature rises, the kinetic energy of its particles increases
•if it melts or it boils, the potential energy of its particles increases.
• The pressure of a gas on a surface is caused by the particles of the gas repeatedly hitting the surface.

Question 10

Specific latent heat

Answer 10

• Latent heat is the energy needed for a substance to change its state
without changing its temperature.
• Specific latent heat of fusion (or of vaporisation) is the energy needed to melt (or to boil) 1 kg of a substance without changing its temperature.
• In latent heat calculations, use the equation E= m L.
• The specific latent heat of ice (or of water) can be measured using a low-voltage heater to melt the ice (or to boil the water).

Question 11

Pressure in gases

Answer 11

• The pressure of a gas is caused by the random impacts of gas molecules on surfaces that are in contact with the gas.
• If the temperature of a gas in a sealed
container is increased, the pressure of the gas increases because:
the molecules move faster so they
hit the surfaces with more force
• the number of impacts per second of gas molecules on the surfaces of a sealed container
increases. so the total force of the impacts increases.
• The unpredictable motion of smoke particles is evidence of the random motion of gas molecules.