---
title: Why does ice remain at the same temperature while it melts?
description: Water is an amazing substance vital for life on earth. It has many properties that can utilised to stabilise temperatures. We can use it to keep goods cool.
---

[Cargo-Wise Blog ](https://www.cargo-wise.co.uk/blog)

# [Why does ice remain at the same temperature while it melts?](https://www.cargo-wise.co.uk/blog/latent-energy-why-does-ice-remain-at-the-same-temperature-while-it-melts)

 Written by [Michael Steedman](https://www.cargo-wise.co.uk/blog/author/michael-steedman) | Jun 30, 2022 12:09:06 PM

In our business we spend a lot of time working out how to keep things cool.

This often involves using **frozen gel** or **water.**

**T**he gel or water is typically contained in polythene sachets (as shown) and is frozen down to −20ºC before being placed around the goods to be protected from high temperatures.

<https://www.cargo-wise.co.uk/gel-ice-packs>

As significant mounts of energy is required to increase the temperature of the ice and convert it to water, we can reduce the amount of energy reaching the ice, by covering the goods with a thermal foil cover that reflects the thermal energy the ice needs to melt. This maintains low temperatures for longer by slowing the transfer of heat keeping products cool for longer.

<https://www.cargo-wise.co.uk/dynachill-thermal-pallet-covers>

Water is one of the few chemical substances on earth that exists in the solid, liquid and gas states at normal temperatures.

## Phase change

Large amounts of energy are needed to change the phase of water, from solid to liquid (ice to water), and liquid to gas (water to steam).

This energy is called latent heat.

It is **latent** or **hidden**, because in phase changes, energy enters or leaves a system **without causing a temperature change** in the system; so, in effect, the energy is hidden.

**So while ice is melting, its temperature does NOT increase. It remains at 0ºC until all the ice has melted. And it requires a lot of heat energy to melt.**

334 kJ is the **energy** needed to melt a kilogram of ice. This is significantly more than other substances. This is a lot of energy as it represents the same amount of energy needed to raise the temperature of 1 kg of liquid water from 0ºC to 79.8ºC. Even more energy is required to vaporise water; This shows that the **energy** required for a **phase change** is enormous compared to energy associated with temperature changes without a phase change.

The graph below shows the effects of phase change by looking at the effect of adding heat into a sample of ice at −20ºC.

From −20ºC to 0ºC the temperature increases linearly **absorbing heat** at a constant rate of 0.50 cal/g⋅ºC.

Once at this temperature, the ice begins to melt until all the ice has melted, absorbing 79.8 cal/g of heat.

### The temperature remains constant at 0ºC during this phase change.

Once all the ice has melted, the temperature of the liquid water rises, absorbing heat at a new constant rate of 1.00 cal/g⋅ºC.

## The specific heat capacity of water

**Specific heat is a measure of heat capacity, or how much heat a material can store when changing temperature.** A high heat capacity means that a substance can absorb a lot of heat before registering a change in temperature.

This [article](https://blog.prepscholar.com/specific-heat-capacity-of-water) explains why water has such a high specific heat capacity. It explains it very clearly and concisely.

This table is taken from this article.

## A real life example

An air freight customer of our using gel ice packs with foil covers, had a **consignment delayed in Qatar**. The goods had to be kept below 8ºC.

Without any external refrigeration facilities, the goods were delivered in a satisfactory condition despite the high temperatures it was exposed to.

This demonstrates the effective combination of using **ice packs with a reflective foil cover** to maintain the desired temperatures over** three days.**

To find out about our **thermal protective products** you can visit our website [here](https://www.cargo-wise.co.uk/).

[View full post](https://www.cargo-wise.co.uk/blog/latent-energy-why-does-ice-remain-at-the-same-temperature-while-it-melts)

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