Calorimetry — Part 1: Specific heat capacity and mixtures: visual lesson, ICSE Class 10 Physics (Science Paper 1)

Lesson

Why is the sand hot and the sea cool?

Part 1 — on a sunny afternoon the beach sand is too hot to walk on, yet the sea stays cool. Different materials need different amounts of heat to warm up.

In this lesson you will

Distinguish heat from temperature and state their units
Use Q = mcΔT and relate heat capacity to specific heat capacity
Apply the principle of mixtures to find a final temperature or a specific heat capacity
Explain effects of the high specific heat capacity of water

Table of specific heat capacities of five substances
Substance	Specific heat capacity (J kg⁻¹ K⁻¹)
Water	4200
Ice	2100
Aluminium	900
Copper	400
Lead	130

Concept

Heat and temperature

Heat is a form of energy that flows from a hotter body to a colder one; SI unit joule (J); also the calorie (1 cal ≈ 4.2 J), the heat needed to warm 1 g of water by 1 °C. Temperature is the degree of hotness that decides the direction of heat flow; SI unit kelvin (K), commonly degree Celsius (°C); a change of 1 °C equals a change of 1 K. A bucket of warm water holds more heat than a cup of boiling water, though its temperature is lower.

Table comparing heat and temperature
Feature	Heat	Temperature
What it is	Energy in transfer	Degree of hotness
SI unit	Joule	Kelvin
Measured with	Calorimeter	Thermometer
Depends on mass?	Yes	No

Concept

Heat capacity and specific heat capacity

Heat capacity $C$ of a body: heat needed to raise its temperature by 1 °C (1 K); unit J K⁻¹. Specific heat capacity $c$ of a substance: heat needed to raise the temperature of 1 kg of it by 1 K; unit J kg⁻¹ K⁻¹ (also J g⁻¹ °C⁻¹). Relation: $C = mc$ . Heat absorbed or given out: $Q = mc\,\Delta T$ . Water has a very high value, $c = 4200\ \text{J kg}^{-1}\ \text{K}^{-1}$ (4.2 J g⁻¹ °C⁻¹).

Table comparing heat capacity and specific heat capacity
Quantity	Symbol	Depends on	SI unit
Heat capacity	C	Material and mass	J K⁻¹
Specific heat capacity	c	Material only	J kg⁻¹ K⁻¹

Cookies