Burning, cooking
Explanation:
Chemical changes that happens in school are:
Cooking of meals
Burning of wastes
Chemical reactions in laboratories
Rusting of iron used in construction
- A chemical change is a change that produces new kinds of substances.
- These changes are usually accompanied by energy and mass changes.
- Most of such changes are not reversible.
Chemical changes are driven by change in chemical properties of matter.
In a school, iron components might begin to rust. This is a chemical change.
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I’d say A. They are theoretical in the fact that they have not been observed directly, but have been confirmed to exist through experimentation.
Lower flammable limit means the lowest concentration of a material that will propagate a flame.
What is hazardous atmosphere?
It is an atmosphere that may expose employees to risk of death, incapacitation, impairment of ability to self-rescue, injury, or acute illness from one or more of following causes
- Flammable gas, vapor, or mist in excess of 10 percent of lower flammable limit (LFL)
- Airborne combustible dust at concentration that meets or exceeds its LFL
What is lower flammable limit?
- It means the lowest concentration of a material that will propagate a flame.
- The LFL is usually expressed as percent by volume of material in air (or other oxidant)
- Atmospheres with concentration of flammable vapors at or above 10 percent of lower explosive limit (LEL) are considered hazardous when located in confined spaces.
- However, atmospheres with flammable vapors below 10 percent of LEL are not necessarily safe. Such atmospheres are too lean to burn
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