According to the Bible, hell isn't separated from God.
If I ascend up into heaven, thou art there: if I make my bed in hell, behold, thou art there. (Psalm 139:8)
The same shall drink of the wine of the wrath of God, which is poured out without mixture into the cup of his indignation; and he shall be tormented with fire and brimstone in the presence of the holy angels, and in the presence of the Lamb: (Revelation 14:10)
Sin is what damns us to hell. If we didn't have sin we could walk into heaven no problem, but the Bible says that all have sinned and come short of the glory of God.
As it is written, There is none righteous, no, not one: There is none that understandeth, there is none that seeketh after God. They are all gone out of the way, they are together become unprofitable; there is none that doeth good, no, not one. (Romans 3:10-12)
So we're all condemned to hell unless we believe on Jesus Christ.
He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God. (John 3:18)
He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him. (John 3:36)
Calvinists just can't understand free will. God chose that all those who believed on Jesus Christ would be saved, but he didn't choose who would believe. We have the option to accept or reject. The Bible says that God wants all people to be saved.
The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance. (2 Peter 3:9)
For this is good and acceptable in the sight of God our Saviour; Who will have all men to be saved, and to come unto the knowledge of the truth. (1 Timothy 2:3-4)
The problem is most people don't believe or they think they can earn their way into heaven through their works. They don't want to humble themselves and admit they're a sinner, deserving of hell, and that we shouldn't enter except that God gave us salvation as a gift we are unworthy of.
For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: Not of works, lest any man should boast. (Ephesians 2:8-9)
For what saith the scripture? Abraham believed God, and it was counted unto him for righteousness. Now to him that worketh is the reward not reckoned of grace, but of debt. But to him that worketh not, but believeth on him that justifieth the ungodly, his faith is counted for righteousness. (Romans 4:3-5)