Solutions
🌟 This Topic is About...
- 🧪 I will investigate and describe how substances dissolve.
- 💧 I will test if a solid can dissolve in water or not.
- 🌍 I will learn how soluble and insoluble substances affect water pollution.
- 🔬 I will explore how to separate a solution into its parts.
- ✏️ I will make drawings of my scientific observations.
- 📏 I will practise measuring liquids accurately.
- ⚗️ I will choose and use the right equipment for an investigation.
- ❓ I will decide the best type of investigation to answer a science question.
- 🔄 I will learn that dissolving is a reversible process.
- 💡 I will ask scientific questions and find the answers through investigation.
Get ready to explore how things mix, dissolve, and can be separated again! 🧂💦✨
🌟 Key Words
- dissolve
- fertilisers
- insoluble
- pesticides
- reversible
- soluble
- solute
- solution
- solvent
- uniform
- universal
📖 Tap to Learn the Meanings!
- 💧 dissolve: When a solid mixes evenly into a liquid and seems to disappear.
- 🌿 fertilisers: Substances added to soil to help plants grow better.
- 🚫 insoluble: A solid that does not dissolve in a liquid.
- 🐞 pesticides: Chemicals used to kill insects and pests that harm crops.
- 🔄 reversible: A process that can be changed back to its original state.
- 💦 soluble: A substance that can dissolve in a liquid.
- 🧂 solute: The solid that dissolves in a liquid.
- 🥤 solution: A liquid mixture made when a solute dissolves in a solvent.
- 🌊 solvent: The liquid that dissolves another substance.
- ⚖️ uniform: When a mixture looks the same all the way through.
- 🌎 universal: Something that works for everything or everyone, like water being a universal solvent.
Great job learning your science words about dissolving and solutions! 🎉
💧 Dissolving in Liquids
When you stir sugar into tea, it seems to disappear. This is because the sugar has dissolved in the tea — its particles spread out between the particles of the liquid.
🧂 Soluble and Insoluble Solids
Solids that can dissolve in a liquid are called soluble. Those that cannot dissolve are insoluble. Dissolving is a type of mixing where the solid’s particles spread evenly through the liquid.
🧪 What Are Solutions?
A solution forms when a solid dissolves in a liquid. The solid is the solute (for example, sugar), and the liquid is the solvent (for example, tea or water). Every solution always has both a solute and a solvent.
🌊 Water as a Universal Solvent
Water can dissolve many substances, which is why it is called the universal solvent. Sea water is a solution of salt and water — the salt is the solute and water is the solvent.
🚯 Water Pollution
Some dissolved substances can be harmful. Polluted water may look clean, but it can contain dissolved chemicals like acids or factory waste. These substances can harm plants, animals, and people.
Fertilisers and pesticides can also dissolve in rainwater and flow into rivers and lakes, causing water pollution.
🌾 Pesticides and Pollution
Many farmers spray chemicals on their crops to kill pests. These chemicals are called pesticides. They can also pollute natural water sources when they dissolve in rainwater and get washed into rivers and the sea.
Insoluble substances in water can also cause pollution. Examples include human body waste, oil, and plastics.
💧 FUN QUESTIONS: Dissolving and Water Pollution
1. What is dissolving? 🤔
🌟 Show me!
2a. Can all solids dissolve? 🧂
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2b. How do we know if a solid has dissolved? 🔍
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3a. Name the two parts of a solution. 🧪
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3b. Give an example of each of the two parts. 🧉
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4. Why is a solution a mixture? 🌀
🌟 Show me!
5. Why is water sometimes called the universal solvent? 🌍
🌟 Show me!
6. Why can’t we sometimes see water pollution? 🧫
🌟 Show me!
7a. Name two soluble substances that cause water pollution. ⚗️
🌟 Show me!
7b. Name two insoluble substances that cause water pollution. 🛢️
🌟 Show me!
8. How do you think the use of pesticides affects the environment? 🐞
🌟 Show me!
🔍 Think like a Scientist 1: Make a Solution
🧰 You will need: water, coloured crystals, a glass jar, a teaspoon, a measuring cylinder, and a watch ⏱️
⚠️ Safety first: Do not touch or taste the crystals. ❌👅
🧪 Steps:
- Measure and pour 100 ml of water into the jar. 💧
- Put a teaspoon of coloured crystals into the jar and observe what happens. 👀
- Describe what you see in the water around the crystals. ✍️
- Draw and label your observations. 🖍️
- Wait five minutes. Can you still see the solid crystals? ⏳
- Think about which substance is the solute and which is the solvent. 💡
- Decide which type of scientific enquiry you used in this investigation. 🧠
❓ Follow-up Questions:
🌟 Tap to See Answers
- 1: The crystals dissolved and the water became coloured. 🌈
- 2: The particles of the crystals spread out between the particles of water — the crystals dissolved. 💧
Brilliant work, young scientist! 👏🌟
🌊 How Solute Particles Spread in Water
When a substance dissolves, the particles of the solute move between the particles of the solvent. The solute particles spread evenly throughout the solvent. Because of this, you cannot see the solute in a solution once it has dissolved.
We say that a solution has a uniform appearance — it looks the same throughout. The diagram below shows how solute particles spread out evenly among water particles when salt dissolves.
💧 Separating a Solution
A solution is a mixture of the solute and the solvent. We can separate most mixtures because the particles of the substances in the mixture are not chemically joined together. But can we separate a solution? Let’s find out!
🔍 Think like a Scientist 2 — How can we get back the salt?
🧠 Background: Most of the salt we eat comes from sea water. Sea water is a solution. How can we get solid salt from sea water? Use your knowledge of evaporation to plan how to get solid salt from a salt solution.
📝 Plan first — think about these questions:
- What materials and equipment will you need?
- Which type of scientific enquiry will you use?
- What will you do?
- Where should you set up the investigation?
- How long must you leave it to get any results?
🚀 Carry out the investigation:
- Carry out the investigation. Make a labelled drawing to show what you used and what you did.
- Make a labelled drawing to show the results of your investigation.
❓ Questions:
- A solution is a mixture. Say how your results show this.
- Complete this sentence to write a conclusion:
I found out that it was possible / impossible to separate a solid from a liquid by evaporation. - Suggest one way you could obtain results faster.
- Could we choose suitable materials and equipment to use?
- Did we work together to plan and carry out the investigation?
- Did we use a suitable method to get back the salt?
🌟 Teacher/Example prompts (optional)
- Possible approach: Leave salty water in a shallow dish in a warm, sunny place. As water evaporates, salt crystals form.
- Faster results: Increase surface area (shallow tray), gentle heat, or airflow — while keeping it a fair test.
- Safety: If using heat, take care with hot equipment and ask an adult to supervise.
💧 Evaporation and Reversible Changes
We can separate the dissolved solute from a solution by evaporation. When the solvent (usually water) evaporates, the solute is left behind as a solid.
We call this a reversible process because we can get back the dissolved solute from the solution without changing it into a new substance.
🔍 Think like a Scientist 3 — Ask and Investigate a Question
🤔 Challenge: Work with a partner to think of a question about dissolving and solutions that you would like to find the answer to.
🧭 Plan your enquiry:
- Decide what type of scientific enquiry you will use to answer your question — for example, a fair test, doing research, pattern seeking, or observing over time.
- Find out the answer to your question by carrying out the investigation.
- Make a presentation to share your findings with the class.
🌟 Helpful tips
- Ask a clear, testable question — e.g., “Does temperature affect how quickly sugar dissolves?”
- Record your observations carefully with drawings or data tables. 📊
- Explain what you found out and how it answers your question. 💡