Atom Frenzy – Lesson 4 – Forces Make Molecules
Students will discover the forces that hold atoms and molecules together. They will explore forces of attraction and repulsion by electrons and protons by exploring magnetic forces and electrostatic forces.
1. Introduction: Introduce our toy atoms and by reviewing key learnings about atoms and molecules from previous lessons. Then present the learning intentions using the Atom Frenzy Lesson 4 PowerPoint.
2. Activity (small groups) – Exploring magnetic forces: Students play with bar magnets to understand magnetic forces and magnetic poles. They also feel the magnetic forces between toy atoms and explore the different arrangements for joining toy atoms.
3. Discussion – How is magnetism made? Review the paper plate atoms, remind students that the electrons are whizzing around very fast. Magnetism is the force made by moving electrons. In magnets the atoms are all lined up so all the electrons are whizzing in the same direction so their tiny forces add up to make the big forces you can feel. Why do the electrons whizz around? Because they are pulled by the protons in the nucleus but their waviness (fuzzy pipe cleaners) stops them getting too close.
4. Activity (various) – Exploring electric forces: Students in groups rub cloth on balloons and plastic rulers to transfer electrons from one to the other. When there are extra electrons their force does not cancel with the opposite force from the protons and we can feel the electric forces of atoms. Students use bits of paper and their own hair to see the electric forces happen. They should be able to see both attraction and repulsion. These forces are forces of static electricity. https://youtu.be/S3sx9BWbEww, https://youtu.be/9jD56GjsNos
5. Discussion – How did we make the electric forces? electrons were transferred from one object to another in the same way that dirt can get rubbed onto our clothes! Electric and magnetic forces have both attraction and repulsion. We say like charges repel, unlike charges attract. Same for magnets: we say like poles repel, unlike poles attract. Why do we use the word pole? We use the word pole because the Earth is a big magnet: That is how compasses work: the south end of a magnetic needle is attracted to the north end of the Earth’s magnet. The north and south poles of the earth are close to the ends of the earth-sized magnet.
6. Activity (small groups) – Forces in molecules: Students return to the magnetic toy atoms, making H2O and CO2, and identifying that it’s electrical forces that hold atoms together.
7. Review and introduce lesson 5: Review the main learning from the lesson and add to the class Word Wall. In addition, let students know that we will learn about solids, liquids, and gases, and how heat interacts with them in the next lessons.
- describe their observations of electric and magnetic attraction and repulsion
- know that atoms and molecules are held together by forces between electrons that come in two forms:
- forces from moving electrons called magnetism
- forces between static (not moving) electrons called static electricity.
- It is advised that teachers test each of the suggested activities before conducting the lesson. Be aware that some of the static electricity activities may not work on humid days.
- Magnets for each group of students, preferably bar magnets with labelled North/South poles, but disk magnets with coloured dots on them may be suitable as well (do not provide students with rare earth magnets without direct supervision)
- Toy magnetic atoms (either magnetic tennis and ping pong balls from the Einstein-First Tatoms kits or alternatively Snatoms)
- Class set of magnetic marbles (optional, ensure these are medium-large and fully encased in plastic)
- Balloons (enough for all students plus demonstration)
- String to hang balloons
- Cloth (woollen is best)
- Plastic rulers
- Tiny pieces of cut or torn up paper (tissue or crêpe paper works best)
In the first lesson, we learnt that atoms are the building blocks of everything, and a group of atoms is called a molecule.
- Are we made of atoms? Yes, we are made up of about 26 different types of atoms, but there are four main ones. With just four elements: oxygen; carbon; hydrogen and nitrogen, we can nearly make a person!
We are mostly hydrogen atoms H, lots of oxygen atoms O, a lot of carbon atoms C, and some nitrogen atoms N. (Teacher info: 62% H, 24% O, 12% C, 1% N by number of atoms)
- Who can work out which molecules have the most hydrogen and oxygen atoms? Water makes up about three quarters of our body.
- Does anyone know of any other atoms in our bodies? Some students might know about other important atoms such as calcium and phosphorous – important for our bones; almost all of our body’s calcium and phosphorous atoms are in our bones; iron in our blood; etc.
In this lesson students will learn about the forces that hold atoms and molecules together. These forces come from the attraction between negative electrons and positive protons, and the movement of electrons which causes magnetism.
Present the learning intentions for this lesson from the Atom Frenzy Lesson 4 PowerPoint.
We recommend viewing the activity video on the right before reading the detailed instructions below.
First, students will explore magnetic forces. It is easy to feel the effect that magnets have on each other. In this lesson students are going to play with some magnets.
- What do you know about magnets? We use them on our fridges, etc; attracted to some metals.
Students will find that they have two different ends – we call these North and South ends: depending on which end we hold near another magnet, sometimes they attract other magnets and at other times they repel – or push them away.
Working in groups, students experiment with magnets, feeling how the magnets attract and repel each other.
Danger: Close teacher supervision needed.
- Never allow students to place the magnets in their mouth or swallow them.
- Do not provide students with unprotected strong rare earth type magnets without direct supervision as these are a swallow hazard and can snap together violently.
- Never provide or demonstrate tiny colourful magnetic balls which are often sold as toys. These magnets represent a significant swallow hazard and are illegal to sell as toys in Australia.
Instruct students to feel some model atoms made from tennis balls and ping pong balls (such as our Tatoms kit), or Snatoms (Teacher supervision required, to prevent loss or misuse of the expensive toy atoms). Feel the forces holding the atoms together and pull the molecules apart by pulling against the forces holding them together.
- What do you feel? A force holding the balls together.
- Why do the atoms stick together? Magnetic forces (which are a type of electrical force).
Note to teacher: We group both magnetic forces and electrostatic forces together and call them electrical forces. They both come from electric charges and are two aspects of the electromagnetic force.
If magnetic marbles are available (larger plastic-encased magnetic balls that are less of a swallow hazard), then students should make some model molecules with these.
- Who has worked out a rule for when magnets attract, and when they repel each other?
- North and North repel, South and South repel – So like poles repel.
- North and South attract and South and North attract – So, opposite poles attract
Now let’s explore a little bit about where the magnetic force comes from:
- Who can remember what atoms are made of? (Refer back to the model atoms made in Lesson 1)
All atoms have a nucleus in their middle. The nucleus is made of protons and neutrons. There are also electrons in atoms. The electrons are in a fuzzy cloud around the nucleus.
Electrons are tiny little bits of negative electric charge. The amazing thing is that moving electrons cause the magnetic forces. This is the principle behind an electromagnet, but also occurs at an atomic level. When all the magnetic fields from each atom align, they combine to produce the magnetic materials we use to make permanent magnets.
We recommend viewing the two activity videos below before reading the detailed activity instructions that follow.
Now students know a little about one of the electric forces, magnetism, they will next learn about the other. In atoms, opposite charges hold them together. The positive charge of the protons in the nucleus and the negative charge of the electrons in the electron cloud attract each other, holding everything together just like if you made a ball-shaped jelly.
Note to teacher: the following activities may not work as well when the weather is very humid; dry conditions are best.
We call this force static electricity or simply the electric force. The electric force comes from the electrons themselves because the electrons can move from one object to another object, causing a build-up of negative electrons on one object, and leaving an excess of positive protons on the other object.
Provide each student with a worksheet (Worksheet – Electric Forces) for the following activities.
Demonstration: Two hanging balloons
Take two balloons and hang them from the ceiling. Ask two students to help by each rubbing a balloon with a cloth.
Then ask the class:
- If someone generates static electricity on an object like a balloon by rubbing it, and then another person touches the balloon, who can work out what might happen? The static electricity will disappear from the balloon, and you’ll have to start the activity over again.
Once both balloons are charged, ask one of the students to bring their balloon close to the other balloon, by moving the string. The class observes what happens. Ask:
- What did we observe? The two balloons pushed apart or repelled each other.
Students record this on their worksheets.
Individual Activity: Picking up pieces of paper
Hand out tiny bits of crepe paper to each student (or get them to tear or cut up some paper into tiny bits, tissues work well). Hand out plastic rulers if students don’t have one.
Ask students to rub their plastic ruler on their uniform to generate static electricity and then see how many bits of paper they can pick up with their ruler. Students record what they observe on their worksheets.
Check for understanding:
- Why do the balloons repel each other? When the balloons were both charged using the cloth, they had the same charge and so they repelled each other. Remember: like charges repel.
- Why does the paper ‘stick’ to the ruler? The ruler is charged by rubbing it on fabric. This attracts the opposite charges on the pieces of paper.
Group Activity: A hair-raising experience
Give each group an inflated balloon and a cloth for their group.
Each student rubs their balloon with the cloth (alternatively, students can rub the balloon on their uniform) and then holds it over the head of another student in their group – this works particularly well with long hair.
Students observe what happens and complete their worksheet.
Now, let’s develop a model to explain what happens when electrons are transferred from one object to another.
- Who can remember what we learnt about the number of protons and electrons in an atom that is not charged? They are the same – the positive charges of the protons and the negative charges of the electrons cancel each other out.
- How did the balloon become charged when rubbed with the cloth? Electrons moved from the cloth to the balloon.
- If a balloon now has more electrons than before, will it be positively charged or negatively charged? It will have more bits of negative charge so it will be negatively charged.
- On the other hand, who can explain what will happen to our cloth? The cloth loses electrons so will have fewer bits of negative charge. As a result, it will have more positive charges than negative ones and will be positively charged.
- Remember that when the charged balloons were brought close together, they repelled each other. Who can explain why? Because they both had a negative charge because they had each ended up with extra electrons that moved onto them from the cloth. We said before that if two objects have the same charge they will repel each other; that is what is happening with these balloons with the same charge.
Provide two H atoms, three O atoms and one C atom (either magnetic toy atoms such as Einstein-First Tatoms or Snatoms atomic models) to each group.
Ask students to use the models to make an H2O and a CO2 molecule. Feel the forces holding the atoms together and pull the molecules apart by pulling against the forces holding them together. Provide each group with a Forces in Molecules worksheet.
- What type of forces hold the atoms together to make the molecule? Electrical forces.
Identify and review all new words and write them on the class Word Wall. In addition, let students know that we will learn about solids, liquids, and gases, and how heat interacts with them in the next lessons.
Optional Extension Task
The following YouTube video may be a useful reference for students who would benefit from extension:
This would be a useful YouTube video to watch preferably with a parent, grandparent, or other carer to reinforce the need to ensure we eat a healthy balanced diet: Calcium and phosphorus are needed for our bones and are about 2.5 percent of our weight and iron is needed to help carry oxygen from our lungs around our body in our blood.
A further interesting reference related to vitamins and is located at: https://www.compoundchem.com/2015/01/13/vitamins/
Don’t worry about the complicated chemical structures, all you need to remember is that vitamins are just large molecules that different parts of our body need and our bodies can’t make all of them on its own.
Electric/Electrical forces: Forces caused by electric charges.
Electrostatic forces: Forces between charges that are not moving.
Magnetic forces: Forces caused by moving charges.
North and south pole: Ends of a magnet.
Positive charge: The charge on a proton.
Negative charge: The charge on an electron.
Charged object: Something that has more protons than electrons is positively charged and something with more electrons than protons is negatively charged.
Neutral: No charge, the number of positive and negative charges balance out.
Attract: To pull together.
Repel: To push apart.