2. why is nuclear fusion able to sustain the life of a star over a long period of time without the input of outside energy?

By nuclear fusion the nuclei of the star masses fuse into each other producing a high energy that creates an outward pressure which releases in the space as electromagnetic radiation that keeps the star alive.

Explanation:

As the gravitational pull gathers gas and dust and forms a huge ball, the temperature of the ball increases immensely causing a nuclear fusion. Through this fusion the contraction in the gas and dust increases ultimately crashing the nuclei of the electrons into each other and fusing them.

A great amount of energy is released in the process that creates a pressure outwardly and balances the inward gravity. When this energy moves out of the outer layer and reaches space it creates electromagnetic radiation that makes the star bright and intact in their position.

d

explanation:

water is a polar molecule. a chemical bond is a force of attraction between atoms or ions. bonds form when atoms share or transfer valence electrons. atoms form chemical bonds to achieve a full outer energy level, which is the most stable arrangement of electrons. so, false

explanation:

in h2o molecule, two water molecules are bonded by a hydrogen bond but the bond between two h - o bonds within a water molecule are covalent. the greater the electronegativity difference, the more ionic the bond is. bonds that are partly ionic are called polar covalent bonds. nonpolar covalent bonds, with equal sharing of the bond electrons, arise when the electronegativities of the two atoms are equal.