Lots of what is a physical and chemical reaction?

See explanation.

Explanation:

In a chemical reaction, the substances change. Put hydrogen and oxygen together and the chemical reaction results in water.

A physical reaction there is a change in form, but the chemical composition remains the same. Take water below freezing, and ice forms - a physical reaction.

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the menstrual cycle – higher tier. negative feedback mechanisms affect the production of hormones in the menstrual cycle. oestrogen also stimulates the release of lh (luteinising hormone) from the pituitary gland, which in turn controls the production of progesterone.