3. Physical changes only change the appearance of a substance, not its chemical composition. Chemical changes cause a substance to change into an entirely substance with a new chemical formula. Chemical changes are also known as chemical reactions.

4.A chemical reaction is usually accompanied by easily observed physical effects, such as the emission of heat and light, the formation of a precipitate, the evolution of gas, or a color change. Absolute confirmation of a chemical change can only be validated by chemical analysis of the products!

5.Precipitate: In chemistry, a solid formed by a change in a solution, often due to a chemical reaction or change in temperature that decreases solubility of a solid. In meteorology a precipitate is liquid or solid water (rain, snow, etc.) falling from the sky.

6.n simple terms, the endothermic reactions absorb energy from the surrounding that is in the form of heat. On the other hand, an exothermic reaction releases energy into the surrounding of the system.

hope this help plz give me a thxs and brainlyest and a five star thx and you welcome let me know if this helped

Explanation:

4 0

2 years ago

Why are iron needles used in compasses

ludmilkaskok [199]

A compass needle points north because the north pole of the magnet inside it is attracted to the south pole of Earth's built-in magnet . And irons are heavily attracked to magnet .So this is why iron needles used in compasses .

4 0

2 years ago