# (c) Change of state

## 5.08 explain why heating a system will change the energy stored within the system and raise its temperature or produce changes of state   ## 5.09 describe the changes that occur when a solid melts to form a liquid, and when a liquid evaporates or boils to form a gas ## 5.10 describe the arrangement and motion of particles in solids, liquids and gases solids:

• Tightly packed
• Held in fixed pattern
• Vibrate about fixed positions

liquids:

• Tightly packed
• Can slide over each other

gasses:

• Very spread out
• Move with rapid, random motion

## 5.11 practical: obtain a temperature–time graph to show the constant temperature during a change of state 1. Remove the boiling tube of stearic acid from
the water bath
2. Place the tube into a beaker of room
temperature water
3. Add a separate thermometer to the water
4. Take readings from the thermometer in the
stearic acid and the water every minute
[Make sure to avoid parallax error while doing so]
5. Note readings in the table below
6. Note on the table when you observe the stearic
acid change from a liquid to a solid.
7. Plot your results in a graph

## 5.12 know that specific heat capacity is the energy required to change the temperature of an object by one degree Celsius per kilogram of mass (J/kg °C)

Specific heat capacity:

• Amount of heat energy required to increase the temperature of 1kg of a substance by 10
• Unit J/kg 0C

## 5.13 use the equation: change in thermal energy: ΔQ = m × c × ΔT

Change in thermal energy [J] = Mass [kg] x Specific heat capacity [J/kg 0C] x Change in temperature [0C]

## 5.14 practical: investigate the specific heat capacity of materials including water and some solids

1. Set up the apparatus as shown the diagram.
2. Make note of all measurements: current (A), potential difference (V), mass (kg).
3. Use the electronic balance to measure the mass of your
4. Record the initial temperature of you block.
5. Switch on the heater and start your stopwatch.
[You will now leave the heater on for 10 minutes]
6. While the heater is switched on take readings from the
Ammeter and the Voltmeter.
7. Use these to calculate the Thermal Energy that will be
supplied to the block in 10 minutes
8. Record the temperature of your block after 10 minutes.
9. Calculate the Change in Temperature
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Section 1: Principles of chemistry

a) States of matter

b) Atoms

c) Atomic structure

d) Relative formula masses and molar volumes of gases

e) Chemical formulae and chemical equations

f) Ionic compounds

g) Covalent substances

h) Metallic crystals

i) Electrolysis

Section 2: Chemistry of the elements

a) The Periodic Table

b) Group 1 elements: lithium, sodium and potassium

c) Group 7 elements: chlorine, bromine and iodine

d) Oxygen and oxides

e) Hydrogen and water

f) Reactivity series

g) Tests for ions and gases

Section 3: Organic chemistry

a) Introduction

b) Alkanes

c) Alkenes

d) Ethanol

Section 4: Physical chemistry

a) Acids, alkalis and salts

b) Energetics

c) Rates of reaction

d) Equilibria

Section 5: Chemistry in industry

a) Extraction and uses of metals

b) Crude oil

c) Synthetic polymers

d) The industrial manufacture of chemicals

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