National 5 Properties of Matter Flashcards
What does the particle model (or kinetic theory) tell us about the particles of a substance?
Normally the particles of a substance are in constant random motion.
Define temperature.
The temperature of a substance is a measure of the mean kinetic energy of its particles
What can happen to the temperature of a substance when heat is gained or lost?
The temperature of a substance can increase when heat is gained
or decrease when heat is lost.
Define specific heat capacity.
Specific heat capacity is the amount of heat energy required to change the temperature of 1 kg of a material by 1 °C.
Eh = cmΔT
(Define symbols and units)
Eh - Heat energy (J)
c - specific heat capacity (J kg-1 °C-1 - see data sheet)
m - mass (kg)
ΔT - Change in temperature (°C)
Example
Calculate the amount of heat energy required to boil a kettle of water (2 kg) from a room temperature of 20 °C.
E<sub>h</sub> = ? c = 4180 J kg<sup>-1</sup> °C<sup>-1</sup> (from data sheet) m = 2 kg ΔT = 100 - 20 = 80 °C
*E<sub>h</sub> = cmΔT E<sub>h</sub> = 4180 x 2 x 80 E<sub>h</sub> = 669 000 J (to 3sf)*
What happens to a substance when heat is gained or lost at its melting or boiling point?
The substance will change state.
Describe what happens to the particles of a substance when it changes state.
The bonds between particles are either loosened or strengthened (meaning the particles gain or lose potential energy).
What happens to the temperature during a change of state?
There is no change in temperature during a change of state.
Eh = ml
(Define symbols and units)
Eh - Heat energy (J)
m - mass (kg)
l - specific latent heat (J kg-1 - see data sheet)
Example
How much water will evaporate when 500 kJ of heat is applied?
Eh = 500 kJ = 500 x 103 J
m - ?
l = 22·6 x 105 J kg-1 (from data sheet)
Eh = ml
500 x 103 = m x 22·6 x 105
m x 22·6 x 105 = 500 x 103
m = 500 x 103/22·6 x 105
m = 0·221 kg
The heating curve (graph of temperature versus time) for a substance is shown.
What is happening in the section labelled A?
(The substance is a solid to begin with because there are only three states of matter with solid being the coolest).
The substance is increasing temperature as a solid.
The heating curve (graph of temperature versus time) for a substance is shown.
What is happening in the section labelled B?
(The substance is a solid to begin with because there are only three states of matter with solid being the coolest).
The substance is changing state from solid to liquid.
(or the substance is melting)
The heating curve (graph of temperature versus time) for a substance is shown.
What is happening in the section labelled C?
(The substance is a solid to begin with because there are only three states of matter with solid being the coolest).
The substance is increasing tempearture as a liquid.
The heating curve (graph of temperature versus time) for a substance is shown.
What is happening in the section labelled D?
(The substance is a solid to begin with because there are only three states of matter with solid being the coolest).
The substance is changing state from liquid to gas.
(or the substance is boiling)
The heating curve (graph of temperature versus time) for a substance is shown.
What is happening in the section labelled E?
(The substance is a solid to begin with because there are only three states of matter with solid being the coolest).
The substance is increasing temperature as a gas.