Topic 7 - Matter Flashcards
(34 cards)
What is density?
Mass per unit volume
How can you find the density of a small object?
- Measure its mass
- Fill a Eureka can and place a measuring cylinder beneath it
- Put object into Eureka can
- Measure the volume of water displaced
- Divide the mass of the object by the volume of water displaced to get the density
Why do some objects float in water?
Because they have a lower density than water itself
What is kinetic theory a way of explaining?
Matter
Where is a substance’s thermal energy store held?
In the kinetic energy stores of the particles
Why does a substance melt/boil?
Particles are given more energy through the heating, os they can move around more and overcome the forces attraction, allowing for the state to change
Finish the sentence: Density of a substance ______ with state, but mass _____‘_
Varies
Doesn’t
What is specific heat capacity of a substance?
The amount of energy needed to cause a 1°C increase in temperature for 1kg of the substance
What is the specific heat capacity of water?
4182J/kg°C
How can you measure the specific heat capacity of a liquid?
- Put the liquid in a polystyrene cup with a thermometer
- Put an electric immersion heater in the cup, and attach to a joulemeter
- Start heating the water
- Stop when you reach an increase of 10°C, and record the reading on the joulemeter
- Rearrange the equation to calculate the specific heat capacity of the liquid
What is specific latent heat?
The energy needed to change 1kg of a substance to another state without changing its temperature
Why is energy required to change the state of a substance?
Because it takes energy to make or break intermolecular bonds
What are the two types of specific latent heat, and what state changes do they refer to?
- Specific Latent Heat of fusion (Melting or Freezing)
- Specific Latent Heat of vaporisation (Evaporation or Condensation)
What creates gas pressure?
Colliding gas particles
What is a closed container of gas an example of?
A closed system - no matter can get in or out
In a sealed container, what is the total outward pressure?
The total force exerted by all of the particles on a unit area of the container walls
What two things does gas temperature vary with?
- Volume
- Temperature
Why does an increase in temperature cause an increase in gas pressure?
Because the force exerted by particles is higher, and there are more collisions due to higher particle speeds
Why does an increase in volume cause a decrease in gas pressure?
Because collisions are less frequent due to the larger distances the particles must travel before coming into contact with a container wall
What is absolute zero?
The coldest anything can get (0K or -273°C)
What are the particles like at absolute zero?
They have so little energy in their kinetic energy stores that they barely move, if at all
What can doing work on a gas increase?
Temperature, as you are transferring energy to the kinetic energy stores of the particles
What makes an object elastic?
If it can be stretched and return to its original shape
What is the elastic limit of an object?
Where an object begins to distort inelastically - can’t return to its original shape
