Answer:
SA node
Explanation:
The SA node (called the pacemaker of the heart) sends out an electrical impulse. The upper heart chambers (atria) contract. The AV node sends an impulse into the ventricles. The lower heart chambers (ventricles) contract or pump.
<span>c.)The product only has different physical properties than the reactants because a chemical reaction occurred.
This is because rust can behave differently than oxygen and iron. This is because a chemical reaction has happened- a chemical reaction is when a new product is formed. Rust can be change chemically and physically. </span>
