Resources: Class presentation, chocolate chips, coconut oil, icecubes, cooking equipment (including a microwave or hob), caster sugar, golden syrup, bicarbonate of soda, a wooden spoon and a food container.
Core Handout (2): A series of questions for the children to answer and provide examples of intrusive and extrusive igneous rocks.
Challenge Handout (4): As above, with some additional questions to challenge the children.
Enquiry Approach - Research
Using information from a variety of sources to answer scientific questions.
Enquiry Skill - Interpreting and communicating results
Using information, results and data to present findings, including oral and written explanations.
Rocket Thinking - Teacher Notes: A key question is an open-ended prompt that can facilitate discussion, address misconceptions or give children the opportunity to probe more deeply into a topic. This question is deliberately placed at the beginning of the unit to allow you to gauge an understanding of the children’s ideas and misconceptions about how rocks might change. Encourage them to think about different types of rock and whether they are all the same.
You may consider linking this rock topic to a geography topic, such as volcanoes. Recap on the children’s knowledge of the Earth’s layers. Use the presentation to teach the children about the formation of igneous rocks. The children will learn about the 2 different types of igneous rocks and will discover the names of rocks and their uses in everyday life.
Once you have finished the presentation, use the following activities to demonstrate to the children how extrusive igneous rocks are formed.
‘Chocolate’ igneous rock:
1. Mix together 340g of chocolate chips with 150ml of coconut oil by heating it until the mixture is smooth.
2. Then, pour the mixture over an ice cube. The chocolate sauce will set hard like igneous rock - specifically obsidian - as the hot chocolate sauce touches the cold ice.
‘Honeycomb’ igneous rock:
1. Mix 200g of caster sugar with 5 tbsp of golden syrup by gently heating it until the sugar has melted. Once the sugar has melted, turn up the heat and simmer until the caramel has turned to an amber colour.
2.Quickly turn off the heat and tip in 2 tsp of bicarbonate of soda. Stir with a wooden spoon until it has disappeared and the mixture is foaming. Pour the mixture into a container and leave it for 1 hour or until the honeycomb is hard and crumbly. Observe the bubbles formed in the honeycomb, which are there because the mixture was cooled while the bubbles of gas from the bicarbonate of soda were still forming. The honeycomb will resemble the texture of pumice.
Career Film: Take a tour around Widemouth Bay and The Etches Collection Museum on the Jurassic Coast to find out about Jonathan Turner's job. Jonathan works as the Head Geologist for Nuclear Waste Management Services.
Expert Film: This is Jonathan Turner. Jonathan works as the Head Geologist at Nuclear Waste Services. Jonathan explains why it is important to understand why and how rocks are formed to do his job as he explores sites to build a Geological Disposal Facility.
Following the children’s demonstration of how extrusive igneous rock is formed, ask them to write a paragraph to explain how each type of igneous rock is formed. Ask them to include a paragraph on how intrusive igneous rock is rock that has been formed inside the Earth.
Challenge Task: Can the children explain the difference between intrusive igneous rocks and extrusive igneous rocks and include these differences in their explanation texts?
Allow the children time to read out their explanation texts to each other. Give them time to edit their work to ensure they have included all the facts.
Igneous rocks are one of the three main types of rocks found on Earth, alongside sedimentary and metamorphic rocks. They form from the solidification of magma or lava, which are molten rocks that are generated by the melting of pre-existing rocks deep within the Earth's crust or mantle. Igneous rocks can be classified based on their texture and composition.
Formation: The formation of igneous rocks involves the cooling and solidification of molten rock material. When magma or lava cools and solidifies, it crystallises and forms an igneous rock. The cooling rate of the molten rock influences the texture of the resulting igneous rock. If the cooling rate is slow, the crystals have more time to grow and the resulting rock has a coarse texture, whereas a fast cooling rate results in a fine-grained texture.
Properties: The properties of igneous rocks are influenced by their texture and composition. Texture refers to the size and arrangement of the mineral crystals within the rock. The texture of an igneous rock can range from fine-grained (invisible to the naked eye) to coarse-grained (large enough to see without magnification). Glassy texture is also common in some igneous rocks that have cooled too quickly to form crystals.
The composition of igneous rocks is determined by the types of minerals present in the rock. Igneous rocks are composed primarily of silicate minerals, which are made up of silicon and oxygen, along with other elements such as aluminium, iron, magnesium, and calcium. The relative amounts of these minerals determine the composition of the rock. Igneous rocks can be classified as felsic (light-coloured, high in silica), intermediate (moderately coloured, intermediate in silica), mafic (dark-coloured, low in silica), or ultramafic (very dark-coloured, extremely low in silica).
Igneous rocks also have various properties such as durability, hardness, and porosity, which make them suitable for a wide range of applications. For example, the durability of igneous rocks like granite and basalt makes them suitable for use in construction and architecture, while the porosity of some igneous rocks like pumice makes them suitable for use in lightweight concrete. Additionally, the different chemical properties of igneous rocks make them useful for studying the Earth's geological history, as different types of igneous rocks are associated with different tectonic settings and geological events.
In summary, igneous rocks are formed through the solidification of molten rock material and are characterised by their texture and composition. Understanding the properties and uses of igneous rocks is important for a range of applications, from construction to geological research.