P6- Molecules and matter Flashcards
What is density
The mass per volume of a substance
3 ways to find the volume of an object
Regular object- Use measurements to calculate volume, calculate mass using a balance
Irregular object- Tie string to it, place in half full measuring cylinder, calculate water level rise
Irregular object- Fill eureka can w water up to spout, place object in, collect water from spout in beaker. Measure displaced water with measuring cylinder
When do objects float on water?
If they have a lower density than water
Physical change?
Example?
No new substances are produced
Changing state
Conservation of mass meaning in states of matter
When a substance changes state the mass stays the same
Particles in solid
Arrangement?
Energy?
Next to each other in fixed positions
Least energetic
Particles in liquid
Arrangement?
Energy?
Move around at random, touch each other
More energetic
Particles in gas
Arrangement?
Energy?
Density?
Move randomly and far apart
Most energetic
Much less dense than solids and liquids
The temperature of water when heated over time
-Increases until 0°, ice starts to melt
-Stays at 0° until all ice has melted
-Increases from 0° to 100°, water starts to boil
-Stays at 100° until all water turns to steam
Specific latent heat
The energy transferred to a substance when it changes state
Where does boiling and evaporation occur in a liquid and when?
Boiling- throughout a liquid at its boiling point
Evaporation- surface of liquid when below boiling point
How to tell the melting and boiling point of a substance from a temp-time graph?
The flat section
Internal energy definition and sum
Kinetic energy + potential energy
The energy of particles caused by their motion and position
Kinetic energy increases by…
Potential energy increases by…
Rise in temperature
Change of state
What determines the state of matter? (particles)
The strength of the forces of attraction between particles
Pressure
The force of the particles colliding with the sides of a container
What happens to gas pressure if temp increases?
-Gas particles move quickly in random directions
-Pressure is collision of particles with sides of container
-Particles gain KE, move quicker, collide w sides of container more frequently w more force
-Higher pressure per surface area
How can the random movement of gas molecules be shown?
By smoke as it moves in a similar unpredictable motion
Latent heat
Energy needed for a substance to change state without changing temp
Latent heat of fusion
The energy needed to change the 1kg of a substance from solid to liquid (melting)
Latent heat of vaporisation
The energy need to change 1kg of a substance from liquid to gas (vaporisation)
Boyle’s law
At a constant temp:
-if volume doubles, pressure halves
-if volume halves, pressure doubles
What happens to gas pressure if volume decreases?
-Particles forced closer together
-More collisions with sides of container
-Increases pressure
What happens to gas if it is compressed rapidly and why?
Temp of gas can increase, work is done, energy not transferred to surroundings quick enough
What happens to gas if it is compressed slowly and why?
Work is done, energy is transferred to surroundings at same rate as energy to gas. Temp of gas doesn’t change
