N5 Heat & Properties of Matter Flashcards
What does the particle model (or kinetic theory) tell us about the particles of a an ideal gas?
The particles of an ideal gas are in constant random motion.
Define temperature.
The temperature of a substance is a measure of the mean kinetic energy of its particles
What happens to the temperature of a substance when it
a) gains heat energy
b) loses heat energy
The temperature of a substance:
a) increases when heat it gains heat energy.
.b) decreases when heat loses. heat energy/
Define the specific heat capacity (c) of a substance.
The specific heat capacity (c) of a substance is the amount of heat energy required to raise the temperature of 1 kg of the substance 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)
Calculate the amount of heat energy required raise the temperature of 2 kg of water in a kettle from room temperature (20 °C) to boiling point (100°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 of a substance 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.
(i.e. 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 in 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.
(i.e. the substance is vaporising (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 in temperature as a gas.