Science 10 – Climate: Energy Flow in Global Systems

Part 3 – Water and Energy Transfer

Water plays an important role in distributing energy around the globe and in weather and climate.

Three main ways that water distributes energy:

1. Ocean currents (movement of water due to convection)

2. Conduction

3. Radiation

Why does water play such an important role?

1. Absorbs a lot of solar radiation.

Water has a low albedo of about 7% so about 93% of the solar radiation that hits the water is absorbed.

2. Able to retain heat

Water has a high specific heat capacity, heat of fusion and heat of vaporization.

Therefore, water retains much of the heat that it absorbs and releases it slowly.

Specific Heat Capacity and Q=mcT

Specific Heat Capacity: the amount of heat required to raise the temperature of 1 g of a substance by 1C.

We can calculate the amount of heat required, or the temperature change when heat is added, for a given mass of a specific substance using the formula:

Q = mcT

This formula and the heat capacities on the right below are given in your data booklet.

Example

Example Calculations

1. Calculate the amount of energy released when 10 000 kg of air cools from 20C to 15C.

2. Calculate the temperature change of 10 000 kg of water when the same amount of energy is released

Think-pair-share

Instructions: Right an answer to the question below. Share it with your partner. Then you may be called upon to share with the class.

Water and land are both hit with similar amounts of solar radiation. Based on their specific heat capacities, which one would you expect to be warmer during the day? During the night?

Land has a lower specific heat capacity to the same amount of energy will heat it up more than water; therefore, it’ll be warmer than water during the day.

At night, there is no incoming radiation. Water’s higher specific heat capacity means it will cool down less for the same amount of energy released at night and will stay warmer for longer.

The higher the specific heat capacity the lower the amount of energy absorbed or released for a given temperature change.

This results in convection currents that blow cool air onto shore in the daytime (sea breeze) and cool air onto the water during the nighttime (land breeze).

Heat of Fusion and Heat of Vaporization

Gizmos Demo

Instructions: Observe the demonstration and answer the questions below. You will be given the opportunity to write answers and discuss with your peers.

1. Describe what is happening with the temperature of water when it is melting and boiling.

2. Describe what is happening to the average molecule speed during a phase change compared to when there is no phase change occurring.

3. Why do you think this is observed/occurs?

When a substance changes phases it is either releasing or absorbing energy.

When a substance melts or evaporates energy is being used to break the attractive forces between molecules.

When a substance freezes or condenses energy is released as molecules interact and build attractive forces.

The amount of energy released or absorbed can be calculated using the heat of fusion and heat of vaporization.

Heat of fusion: energy required to melt or released when freezing 1 mol of a substance (without changing temperature)

Q = nHfus

Heat of vaporization: energy required to boil or released when condensing 1 mol of a substance (without changing temperature)

Q = nHvap

Heating Curve of Water

Example Calculations

1. People sweat in order to maintain our body temperature during exercise. Sweat cools us through the evaporation of the water. Mr. Funk produced 1.2 L or 1.2 kg of sweat during a run. Determine the amount of heat used to evaporate this amount of sweat. (We will assume the sweat is water).

or 2.7 x 103 kJ

Part 4 – Biomes and Climatographs

Biomes: major geographic region with similar environmental conditions and life forms.

Biomes are an open system.

Adaptations: a characteristic or function that allows an organism to survive.

Ex. The white fur of a snow hare

Thorns on a rose bush

Migration

Ability of bears to hibernate

Climatographs: Show average precipitation and temperatures as both of these are significant in the climate of a region.