In the 17th, 18th and 19th centuries, new countries were being discovered and explored. James Cook's voyages took him to Australia and the Antarctic. John Franklin headed north to the Arctic Circle in search of the North West Passage.

Icebergs

Download a pdf of the instructions here.

You will need...

Several plastic cups
Two small plastic water bottles
Water
Salt
A jug
Coffee filters or filter paper
Stickers to label your cups.

How long will it take?

It will take about half an hour to put this experiment together, but then several hours to wait for enough of the ice to freeze to get some good samples.

What to do...

1.  Have a look at the students' section to see the instructions for this experiment.

2.  Students may want to work in small groups.  If several students are producing salt water and ice water you can have a taste test to find the least salty sample!

Ocean Currents

Download a pdf of the instructions here.

You will need...

Two glasses
Food colouring
Water
Salt
A syringe

How long will it take?

This is a very short experiment and will take only around 15 minutes.

What to do...

1.  Follow the instructions in the students' section.

2.  You may want to carry this out as a demonstration while the students are making their sea ice.

 

Curriculum Links 

Science:

Working Scientifically

 

Upper key stage 2 Year 4
States of matter

 

Upper key stage 2 Year 5
Properties and changes of materials

 

Upper key stage 2 Year 6
Light

Geograhpy:

Geographical skills and fieldwork

History:

A study of an aspect or theme in British history that extends pupils' chronological knowledge beyond 1066

 

Scottish Curriculum

Science 

SCN 2-05a

Planet Earth - Processes of the planet.

 

SCN 2-15a

Materials - Properties and uses of substances.

 

SCN 2-17a

Materials - Earth's materials.

 

SCN 2-18a

Materials - Chemical changes

have investigated different water samples from the environment and explored methods that can be used to clean and conserve water and I am aware of the properties and uses of water.

 

SCN 2-19a

Materials - Chemical changes 

Safely demonstrating simple chemical reactions using everyday chemicals and showing an appreciation of a chemical reaction as being a change in which different materials are made.

Social Studies

 

SOC 2-01a

People, past events and societies

Using primary and secondary sources selectively to research events in the past

 

SOC 2-06a

Discussing why people and events from a particular time in the past were important, placing them within a historical sequence

 

SOC 2-12a

Comparing my local area with a contrasting area outside Britain; investigating the main features of weather and climate and discussing the impact on living things

John Franklin and the North Pole

John Franklin was an Arctic explorer.  Two early expeditions to the Arctic were followed by  seven years as governor of Tasmania, an island off the coast of Australia.  When he returned to England he decided to set out to find the North West Passage.

northwest passage

The North West Passage is a route across the Arctic Ocean found at the top of Canada and Alaska, which connects the Atlantic Ocean with the Pacific Ocean.  In winter it is completely sealed with ice, and frequently it is sealed in the in summer too.  However, as climate change warms the planet, the North West Passage is increasingly easy to travel along.

By 1845 there was more technology available to Franklin than there was to James Cook on his expeditions some 70 years earlier.  There were steam engines which could power and heat the ships, and equipment to make fresh water from sea water.  The new idea of preserving food in cans had been invented in 1810, and canned food was brought on Franklin's expedition.

Despite all of this they didn't find the North West Passage.  Their ships became trapped in the ice and they died trying to head south to safety.

mirage

Mirages don't just happen in the desert  - these drawings made in 1799 show how images of ships and mountains can appear at sea too. 

Mirages happen when light bends as it passes from colder air near the sea to warmer air higher up.  To our eyes it looks like this light has come from a object floating upside down in the air!  A mirage that looked like mountains may have prevented a later expedition from finding the North West Passage.

mirage diagram_500

 

Icebergs

sea iceOn one of James Cook's voyages he brought onboard small icebergs which were made of fresh water for the crew to drink.  People at that time believed that sea water couldn't freeze, and this is why they thought there must be a route across the north of Canada.

Icebergs found at the poles are usually formed by glaciers - rivers of ice - which flow over the land and break off into the sea.  At the North Pole this land could be Greenland or Canada, while at the South Pole this land is the Antarctic.

As well as icebergs causing a hazard to shipping in the North West Passage the sea does freeze and this is known as sea ice. 

 

Make your own sea ice

Download a pdf of the instructions here.

You will need...

Several plastic cups
Two small plastic water bottles
Water
Salt
A jug
Coffee filters or filter paper
Stickers to label your cups.

What to do...

1.  Start by labelling you cups.  One is labelled 'ice water' the other 'salt water'.

2.  Heat up some water - you may need an adult to help with this.  It doesn't have to be very hot but it helps with dissolving the salt.

3.  Pour some water (around 500ml) into a jug with about two tablespoons of salt.  Stir until you get most of the salt to dissolve.

4.  Pour this salty water through a coffee filter into an empty water bottle.

5.  Fill the second bottle with plain water to compare how the plain water and salt water freezes.

6.  Pop both bottles in a freezer for about two hours.

7.  When the two hours are up, take both bottles out and examine how the water in each one is freezing.  The salt water should be freezing in large flat crystals, while the plain water freezes into one complete crystal which you will almost be able to see through.  You can take the plain water ice out of the freezer now, as you don't need it any more.

8.  Put the salt water bottle back into the freezer for another few hours, checking on it every now and then; you do not want the salt water to freeze completely.  When it is mostly frozen but still 'slushy' open the salt water bottle up and pour the unfrozen water into the cup labelled 'salt water'.  Drain as much of the water out as you can - you can squeeze the bottle and drain the ice a bit like a sponge.

9.  Once all the free water has drained off, shake up the bottle and squeeze it to break up the ice.  Now tip this broken ice into the cup labelled 'ice water'.  Try a piece of the ice!  You should notice that once you get through the salty outside of the ice, the inside tastes like a normal ice cube.

10.  Let the ice melt in the 'salt water' cup (you can put the cup in some warm water to speed up the melting).

11.  Put both cups next to each other.  Dip you finger in the water in one cup and taste it.  Have a drink of plain water from a separate glass, then dip your finger in the water in the other cup and taste that. Does one taste saltier than the other?

12.  Use a syringe to take 10cm3 from each of the cups.  Put each sample in a separate coloured bowl.  Leave in a warm place where the water will evaporate leaving just the salt.  Does one leave more salt behind than the other?

What is happening?

The salt gets in the way of the ice crystals forming in the freezing water.   This is why the salty ice looks difference from the water ice: water ice can form a single large crystal.  As the salty ice freezes some of the salt is also pushed out of the way, so the liquid becomes more salty and the solid ice is made mainly of pure water.

 

Ocean Currents

Download a pdf of the instructions here.

When sea ice forms, the sea water around it is both very cold and very salty.  This water is very important for creating currents in the sea, which are like vast rivers of water that flow within the oceans!

You will need...

Two glasses
Food colouring
Water
Salt
A syringe

What to do...

ocean currents1.  Fill one glass half full of warm water.

2.  Fill the other glass with colder water and add a few drops of food colouring.  Add a tablespoon of salt and stir until it is dissolved.

3.  Take a syringe full of this cold, salty coloured water and pour it carefully down the side of the glass with the clear water.  Add another syringe full and have a look at where the salty water has settled.  Despite pouring it in the top, the colder salty water should have sunk to the bottom of the glass.

What is happening?

The cold, salty water is more dense (heavier) than fresh water.  It sinks underneath the fresh water.

This is what happens at the Earth's poles.  The freezing sea purifies the ice and the more salty water sinks to the ocean floor (in the Antarctic this is called the Antarctic bottom water).  This sinking water helps 'pull' warmer water from the tropics to the poles to take its place.  Luckily for us in the UK, this warm water heats our country, making it much warmer than we might expect given how far north we are. 

What happens if the Arctic ice melts, or if glaciers melt and start adding more lighter fresh water to the ocean in the Arctic?  Scientists are currently studying what effect this may have, but it could dramatically change our climate.