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Session 1. Safe Practical Work with Low-Cost Local Materials
Objective. Choose cheap local materials for a clear science idea, check home-made instruments against a known value, and run a three-question risk assessment that ends in a decision: pupil practical, demonstration or replace.
Many teachers skip practical work because they have no equipment or are afraid something will go wrong. Both worries have the same answer: a little preparation. A home-made instrument that you have checked gives better data than a shop instrument no one has tested, and a five-minute risk assessment makes pupils and you calmer. This lesson goes beyond the key ideas: it shows how to build and check three simple instruments and how to write a risk assessment you will actually use.
Key ideas
Low cost does not mean low quality
- Start with the idea pupils must see, then pick the cheapest safe material that shows it: plastic bottles, balloons, string, stones, coins, cardboard, cloth, sand, soil, clay pots, vinegar, baking soda, salt.
- Ask pupils to bring clean recycled items a week ahead, and keep a box of shared supplies so no lesson depends on one pupil's family.
- Course 8.3 showed how to plan the inquiry. Here we make the equipment trustworthy and the work safe.
Check your instruments before pupils use them
- A bottle cylinder, ruler balance, sand timer or string pendulum is only as good as its check against a known value: pour a known 100 ml three times, weigh 1 litre of water (about 1 kg), time 60 counted seconds.
- Look at the pattern. Readings that agree but are all 10 ml off show a systematic error: re-mark the scale. Readings that scatter show a problem with the tool or the technique: fix it first.
- Write the result on the tool itself ('reads 10 ml low, add 10') so every class can use it honestly.
A risk assessment in three questions
- 1 What could go wrong? Think of heat and hot water, sharp edges and broken glass, chemicals, electricity, spills on the floor, flames, allergies and tasting.
- 2 Who could be hurt, and how badly? A cut finger and a scald are not the same. 3 What will I do to prevent it, and what will I do if it happens?
- Use batteries only, never mains sockets. Never taste or smell unknown things. Use garden soil you know, not soil from a sprayed field. Follow your school's safety rules first; the head of studies decides what needs approval.
Decide: pupil practical, demonstration or replace
- Pupil practical if the risk is low or the control is simple (warm water, a battery, vinegar in small amounts with eye protection).
- Teacher demonstration if there is a flame or hot liquid: pupils watch from 2 metres while you explain. Replace the activity if you cannot make it safe, for example by using a model or a video you have already seen.
- For 40 pupils use a routine: bags under tables, one stop signal, equipment monitors, spills reported at once, hands washed with soap, a 3-minute clean-up. Know where the first-aid kit is.
From idea to a safe practical
Three home-made instruments and how to check each
A ruler balance is a ruler resting on a pencil at its middle. Check it by putting two identical full bottles at equal distances on both sides: it should sit level. If it tips, move the pencil or the ruler until it does, and mark the balance point. A bottle cylinder is checked by pouring a known 100 ml from a medicine cup into it three times and marking the water level each time; read at eye level on a flat table.
A string-and-stone pendulum is checked with a clock that has a second hand: count 10 swings against 60 seconds. Always record what the check found on the instrument itself ('reads 10 ml low'). Keep the instruments in a labelled box so another teacher can use them with the same honesty.
A risk assessment you will actually use
Keep it to half a page: the practical, the main hazard, who might be hurt, the control, and the decision. Think about both how likely something is and how serious it would be: a small spill is likely and harmless; a scald is unlikely but serious, so it gets a stronger control. Ask pupils to find the hazards in the equipment before they start; pupils who spot a hazard themselves follow the rule more willingly.
Decide in advance what you will do if something goes wrong: stop the work, make the area safe, help the pupil, tell the school nurse or head, and write down what happened. Ask families on a form about allergies. Always follow your school's own safety rules first.
Examples from the classroom
The ruler that tipped
Scene. Jasur's Grade 6 class in Samarkand compares the masses of stones on a ruler balance. Before they begin, he puts two identical 500 ml bottles of water on the two sides. The ruler tips to the left. The pencil is not at the middle: the ruler is 30 cm long and the pencil sits at 13 cm. They move it to 15 cm, mark it, and start.
Insight. Checking against a known mass found a fault in the instrument before it spoiled the data.
Pupils find the hazards
Scene. Dilnoza in Tashkent plans vinegar and baking soda in bottles with balloons for Grade 5. She shows the equipment and asks, 'What could go wrong?' Pupils say: vinegar in the eye, the balloon flying off, a spill on the floor. They agree small amounts, a tray, and 'never point a bottle at anyone'. She adds eye protection. The lesson runs calmly with 36 pupils.
Insight. When pupils name the hazards, the controls become their rules, not yours.
A demonstration with a question
Scene. Malika in Fergana decides that a burning candle under a jar is a teacher demonstration. Pupils sit 2 metres away, and she holds the matches. Before lighting, each pupil writes how many seconds the candle will burn under a small jar and under a big jar. Two pupils time the result. The class is quiet and active, and nobody touched a flame.
Insight. A demonstration is still active learning when pupils predict, observe and explain.
Common pitfalls
- Using a home-made instrument without checking it against a known value.
- Treating a risk assessment as paperwork to be filled in once and filed away.
- Banning a useful practical because of one hazard when one extra control would make it safe.
- Forgetting that pupils hold the equipment longer than you plan, and that spills happen on the way to the table.
Risk-Assess Six Practicals and Check Three Cylinders
- Open the Activity Kit: six SAMPLE practical cards (A to F) and three bottle cylinders with readings. Facilitator reminds everyone of the three risk questions (5 min, plenary).
- Pairs (12 min): fill the risk table for cards A to F: main hazard, one control measure, and a decision (pupil practical, demonstration or replace).
- Pairs (8 min): a 100 ml measure was poured into each of three bottle cylinders three times. Decide which cylinder can be used as it is, which needs a correction and which must be fixed first.
- Groups (10 min): compare with another pair. Agree one safety routine for a class of 40 in five lines (what pupils do, what you do).
- Alone (5 min): write your classroom action task from the Kit.
Your facilitator will guide you through this activity in the session.
Questions to discuss
- Which card was hardest to decide, and what tipped the decision?
- What did the three cylinders teach you about trusting a home-made instrument?
- Which practical that you currently avoid could you run with one extra control?
Reflect
- Which practical lesson do you avoid because of materials or safety? What exactly stops you?
- Which measuring tool in your room has never been checked?
- Who in your school could review your risk table with you?
Try it tomorrow
- Check one measuring tool in your room against a known value and write the result on it.
- Write a half-page risk table for the next practical lesson and ask the class to add one hazard.
- Rehearse the 'stop' signal and a three-minute clean-up once with your class.
Further reading and links
Check the tool against a known value, ask three risk questions, and decide: pupil practical, demonstration or replace.