Physical Science · Grade 5 Mr. Mohamed Fawzy Week 6 — Food & Energy
Week 6 · Unit Opener

Food
& Energy

Every animal on Earth must eat. This week you find out why — and trace the energy in your lunch all the way back to where it started.

Taught by Mr. Mohamed Fawzy
ReadLookDoCheck
LookStart here · 4 minutes

Why does anything have to eat at all?

All animals on our planet need food in order to survive. You eat throughout the day. If you have a pet, you provide food for it too. You have probably seen animals outside eating grass, nuts, or even other animals.

But why? A rock does not eat. A car does not eat — though it does need fuel. What is it about living things that makes food necessary?

Think about this first

Name three things your body is doing right now that you are not consciously controlling. All of them cost something. That cost is what food pays for.

nuts grass worms DIFFERENT FOOD. SAME REASON.
Every one of these animals is after the same thing, hidden inside very different meals.
ReadCore idea 1 of 4

Animals eat because they require energy

Animals eat because they require energy. Energy is the ability to do work. Without energy, animals cannot survive.

"Work" here does not mean a job. In science, work means making something happen — moving, building, warming, repairing.

Growing

Building new bone, muscle, and skin takes energy — and it takes raw material, which also comes from food.

Repairing

Healing a scraped knee or fighting off an illness costs energy. This is why rest and food matter when you are unwell.

Moving

Every step, every blink, every heartbeat. Your heart alone beats around 100,000 times a day without ever stopping to rest.

The part that surprises people Most of the energy from food is not used for running around. It is spent on the invisible work of simply staying alive — keeping your body warm, pumping blood, breathing, and running your brain. Your brain alone uses about a fifth of your body's energy, even while you sleep.
LookThis is last week's lesson again

Your body releases energy with a chemical reaction

Last week you learned that chemical reactions rearrange matter and release energy. That is exactly what happens inside your cells.

REACTANTS sugar from food + oxygen from breathing in your cells ENERGY grow · repair · move PRODUCTS C CO₂ H₂O breathed out
You breathe in one reactant and eat the other. The products leave every time you exhale.
Teacher note Ask students to breathe onto a cold mirror. The fog is the water product of this reaction, made inside their own cells. It is the most direct evidence of respiration available in a classroom.
ReadCore idea 2 of 4

Trace it back far enough and you always reach the Sun

Animals cannot make their own food. They have to get energy by eating something else. Plants can — and that changes everything.

Producers

Plants capture energy from sunlight and use it to build sugar out of carbon dioxide and water. This reaction is called photosynthesis.

They are called producers because they produce their own food. They are the doorway that energy uses to enter every living thing on Earth.

Consumers

Animals are consumers. They must consume something that already holds energy — a plant, or an animal that ate a plant.

However far down the chain you are, the energy in your meal was captured by a plant from sunlight at some point.

Try tracing it yourself A cheeseburger. The beef came from a cow. The cow ate grass. The grass caught sunlight. The bun came from wheat, which also caught sunlight. Every calorie on that plate started as light from a star 150 million kilometres away.
DoEnergy lab · click each level

Watch the energy shrink at every step

Start at the Sun and click your way up the chain. Watch the energy bar. Something important happens at each level.

THE SUN ENERGY: 100%

Where did the missing energy go?

It was used. Every animal spends most of what it eats on staying alive — moving, staying warm, breathing. Only about a tenth is left stored in its body for whatever eats it next. This is why food chains are short: after four or five links there is simply not enough energy left to support another animal.

DoClass sort · 4 minutes

Producer or consumer?

Ask one question: can it make its own food from sunlight? Tap your answer.

CheckQuick check · no score

Quick check: energy from food

DoExperiment 1 · 10 minutes

Experiment: proving plants need light

Materials

  • Two similar potted plants, or two trays of grass seed
  • A cardboard box big enough to cover one
  • Water and a ruler
  • Small squares of black paper and paperclips

Part A — the whole plant

  1. Put plant 1 in a sunny window. Cover plant 2 completely with the box.
  2. Water both exactly the same amount on the same days. Everything except light must stay identical.
  3. After one week, uncover plant 2. Compare colour, height, and how firm the leaves are.

Part B — one leaf

  1. On the sunny plant, clip a square of black paper over the middle of one healthy leaf.
  2. After four or five days, take the paper off and look at the shape underneath.

What happened

Part A: the covered plant is pale yellow, thin, and floppy. It may even be taller — stretching desperately in search of light. It had water and air but no energy source, so it could not build food.

Part B: a pale patch in the exact shape of the paper. This is the strongest evidence in the whole unit: the plant only made food where light landed. Same leaf, same water, same air — only light was different.

LIGHT · green DARK BOX NO LIGHT · pale same water · same air only light was changed
Changing exactly one variable is what makes this a fair test.
ReadCore idea 3 of 4

Food is energy in storage

Energy cannot be held in a bucket. Living things store it the only way they can: inside chemical bonds. When your cells break those bonds apart, the energy is released and put to work.

Why food packages list Calories

A Calorie is simply a unit for measuring energy, like grams measure mass. A number on a package tells you how much energy that food can release — nothing more mysterious than that.

Different foods, different jobs

Carbohydrates release energy quickly. Fats store more energy per gram, which is why animals that hibernate build up fat first. Proteins are used mostly as building material for growth and repair rather than as fuel.

A nice connection Coal and oil are the stored remains of ancient plants and the animals that ate them. When a power plant burns coal, it is releasing sunlight that was captured 300 million years ago. Even fossil fuels are food chains, just very old ones.
DoExperiment 2 · 12 minutes

Experiment: finding the starch in your food

Materials

  • Iodine solution and a dropper (adult handles this)
  • A white plate or paper towel
  • Test foods: potato, bread, rice, apple slice, cucumber, cheese
  • Safety goggles
Safety first Iodine stains skin, clothing, and desks, and it is not for tasting. Goggles on, an adult does the dropping, and nothing from this experiment gets eaten afterwards.

Steps

  1. Lay a small piece of each food on the plate, well separated.
  2. Predict which ones store their energy as starch. Write your predictions down first.
  3. Place one drop of iodine on each piece.
  4. Watch for about thirty seconds. Record which turned blue-black.

What happened

Blue-black: potato, bread, and rice. Stays brown: apple, cucumber, cheese.

Iodine turns blue-black only when starch is present, so it is a chemical test — a colour change signalling a reaction, exactly like the signs you learned last week.

Starch is how plants pack sugar away for storage. Potatoes are full of it because a potato is the plant's underground energy store. The apple has energy too, but stored as sugar instead, which iodine does not detect.

potato bread rice apple cucumber black = starch brown = none PREDICT FIRST
A colour change is the signal. This is a chemical test, not a taste test.
ReadEnergy explains the living world

Four things this explains

Why bears hibernate

Winter means almost no food available. A bear eats heavily in autumn to build an energy store, then slows its body down so it burns through that store as slowly as possible.

Why there are far more rabbits than foxes

Only about a tenth of the energy passes up each level of a food chain. A landscape can feed many rabbits, but it takes a great many rabbits to support one fox.

Why you feel warm

The reaction inside your cells releases heat as well as usable energy. Your body temperature is a by-product of the energy your food is releasing right now.

Why a volcano needs no food

Volcanoes, wind, and waves all carry enormous energy, but it comes from heat and motion inside the Earth — not from food. Only living things need to eat.

Teacher note Keep this unit at the level of energy flow through ecosystems. Discussions about what individual students should or should not eat belong with families and the school nurse, not in the physical science lesson.
CheckTap a card to flip it

Week 6 vocabulary

Cover the definition, say it in your own words, then flip to compare.

CheckEnd of week quiz · 8 questions

End of week quiz

0 / 8 Answer each question once. Read the explanation even when you are right.
CheckAll six weeks · final review

The whole unit, in one thread

Every week connected to the one before it. Here is the thread:

WeekTopicThe one sentence to remember
1Particles of MatterEverything is made of atoms, far too small to see.
2Properties of MatterProperties are how we describe matter, and they tell us what it will do.
3Heating & CoolingTemperature is particle speed, and it decides solid, liquid, or gas.
4GravityMore mass means more pull; an orbit is a fall that keeps missing.
5Chemical ReactionsAtoms rearrange into new substances, and none are ever destroyed.
6Food & EnergyLiving things run a chemical reaction to release energy that started as sunlight.
The thread Matter is made of atoms → those atoms give matter its properties → heat changes how they move → their mass gives them gravity → they rearrange in reactions → and one of those reactions is what keeps you alive.
ReadExit ticket

What you can now explain

  • Animals need food because they require energy, and energy is the ability to do work.
  • That energy pays for growing, repairing, and moving — and mostly for simply staying alive.
  • Your cells release it with a chemical reaction: sugar + oxygen → energy + carbon dioxide + water.
  • Producers make their own food from sunlight. Consumers must eat something else.
  • Only about one tenth of the energy passes to the next level of a food chain, which is why chains are short.
  • Trace any meal back far enough and the energy came from the Sun.

Exit ticket · write three sentences

  1. Name one thing your body is doing right now that requires energy from food.
  2. Trace a food chain from the Sun to something you ate this week, with at least three links.
  3. Explain why a volcanic eruption does not require energy from food.

You finished the unit

Six weeks ago you could not have explained why a paper towel stays dry in an upside-down cup. Now you can explain that, plus orbits, phase changes, rust, and where the energy in your breakfast came from.

Final challenge: pick any object in this room and explain it using an idea from all six weeks. Everything in here can be described that way — that is what it means to think like a scientist.