Ascientist is performing an experiment on a powder. which of the following is a sign that a chemical change has definitely occurred during his experiment?

the powder catches on fire.
the powder releases bubbles.
the powder heats up.
the powder breaks apart into smaller particles.

How air particles exert a pressure on the inside of the balloon

The alkali metals (group 1) consist of lithium (3), sodium (11), potassium (19), rubidium (37), cesium (55), and francium (87). they are soft, metallic solids with low densities and low melting points. based on the data shown in figure 1, how many valence electrons do alkali metals share?

Gymnast always perform on padded mats. how does the mats protect the gymnast