7. Solids Liquids + gases Flashcards
What is mass?
Amount of matter
What is volume?
Amount of space
What is density?
How compact the matter is - tells you how much matter is in a particular volume
What is the density equation?
Density kg/m3= mass(g/kg)/volume (cm3/m3)
p=m/v
How do you convert cm2 to m2?
Divide by 10,000
How do you find the density of solid objects?
- Measure mass with balance
- Measure length, width + height of object
- Calculate volume using volume = length x width x height
- Calculate density
- Repeat for different objects
How do you find the density using water displacement with a Eureka can?
- Measure mass using balance
- Fill eureka can up to spout
- Add object + measure water that leaves eureka can - this is equal to volume of object
- Calculate density
- Repeat for different objects
How do you find density with water displacement with a measuring cylinder?
- Measure mass using a balance
- Measure initial volume of water in measuring cylinder
- Add object = measure new reading in measuring cylinder
- Calculate volume of object by subtracting volume readings
- Calculate density
- Repeat for different objects
What are 4 common ways to reduce the accuracy of these experiments?
- Not zeroing balance
- Not taking measurement from measuring cylinder at eye level (parallax error)
- Placing measuring cylinder on uneven surface before taking a measurement
- Not filling eureka can up to the spout
Would a measuring cylinder or beaker lead to more precise measurements?
Measuring cylinder
Objects made out of the same material have the same…
Density
An object will float if its average density is…
Less than the liquid it is floating in
Why does a boat float?
Average density of boat and air inside is less than density of water - air is much less dense than water
What is pressure a measure of?
How spread out a force is
As you increase the size of the force you ..
Increase the size of the pressure
As you decrease the size of the area over which a force acts, you increase
The pressure`
Pressure equation
Pressure = force/area
Measured in pascals (Pa) or N/cm2
Area is measured in m2 (so don’t forget to convert)
What causes a balloon to be forced outward when it is filled with a gas?
- more particles inside balloon
- more collisions with the balloon
- greater outward pressure
Does pressure increase in depth?
Yes
Why are Magdeburg hemispheres forced together when there is a vacuum inside them?
- no outward pressure cos vacuum inside
- inward pressure caused by atmosphere pushing them together
What is the pressure difference equation?
Pressure difference = density x g x depth
P = pgh
Explain how pressure is exerted by gases in containers
- particles continually colliding w each other + walls of container
- exert force on wall
- pressure is the combined force of all the collisions
Explain why heating a material will change the energy stored in the material and raise its temperature?
- particles increase in speed
- kinetic energy increases
- thermal store increases
What are the differences between evaporation and boiling?
Boiling occurs at boiling point, but evaporation occurs below boiling point
Evaporation only occurs at surface, whereas boiling occurs throughout the liquid
A source of energy is needed for boiling whereas energy is taken from the surroundings for evaporation
What happens during evaporation?
- faster particles near surface able to escape liquid
- avg kinetic energy of remaining particles is lower than before
- lower avg kinetic energy corresponds to lower temp
- thermal energy stored in surroundings is transferred to cooler liquid by heating
Does the temp remain constant during a change in state?
Yes
What is the change in thermal energy equation?
Triangle E = m x c x triangle T
What is Boyle’s law?
For a gas with a constant mass and temp the pressure will increase when the volume decreases
Why does boyle’s law occur/
- elastic collisions with the particles and container cause gas to exert an outward force on container
- when gas expands at constant emp speed of particles is unchanged
- force of each collision is unchanged
- however particles collide less frequently, resulting in avg force and pressure to decrease
Why does boyle’s law occur/
- elastic collisions with the particles and container cause gas to exert an outward force on container
- when gas expands at constant emp speed of particles is unchanged
- force of each collision is unchanged
- however particles collide less frequently, resulting in avg force and pressure to decrease
What is the equation for volume and pressure of a fixed mass of gas at constant temp?
P1 x V1 = P2 x V2
P1 is initial pressure
P2 is final pressure
V1 is initial vol
V2 is final vol
What units do you use for pressure?
Pascals
Pa
What happens to the particles of a gas when temp increases?
- as temp of gas increases, speed and avg kinetic energy of particles increases
What is absolute zero?
-273 degrees Celsius
Where particles stop moving
How to convert between kelvin and Celsius?
Temp (K) = temp (c) + 273
Temp (c) = temp (K) -273
-273 c = 0K
What is the relationship between kinetic energy and absolute temp of the gas? (Measured in kelvin)
Directly proportional
Eg as temp of gas doubles kinetic energy of particles would double
Why is pressure directly proportional to absolute temperature (kelvin) if volume remains fixed?
- as temp increases speed and kinetic energy of particles increases
- increases force of each collision and frequency of each collision
- pressure that gas exerts increases
What is the relationship between pressure and volume?
As pressure increases volume decreases
What is the pressure law?
P1/T1 = P2/T2
T1 = initial absolute temp, T2 = final absolute temp both in kelvin
