Heat-sealed seams and boiler: what they have in common

1. Step 1. Heat-sealed seams — is part of — Plastic bag. Heat-sealing of the bottom and sides.
2. Step 2. Plastic bag — is made of — Polyethylene. Polyethylene.
3. Step 3. Polyethylene — is made of — Crude oil. Made from petroleum products.
4. Step 4. Crude oil — uses — Oil well. Oil is extracted from wells.
5. Step 5. Oil well — is made of — Wrought iron. The casing pipes are iron.
6. Step 6. Wrought iron — is material for — Boiler. Later — made of sheet wrought iron.

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