Wikipedia to the rescue here:

“Many clay products require the addition of other materials to add strength and durability. In the case of bricks in OT Egypt -- river clay is usually composed of very fine particles and so would dry slowly. Adding straw would ‘open up’ the clay, allowing it to dry more readily and so be more promptly and successfully fired. In addition to aiding in drying, the linear nature of straw adds stability to the clay brick in much the same way that rebar or wire mesh reinforce modern day concrete. Bricks made without straw would break and crumble easily.”

So yes, it was very important that straw be added to those bricks.

2. Exodus 6:3. What is the Lord’s Name?

Difficult passage, discussed by many over the centuries. God says here that He was not known to the Patriarchs by the name Jehovah, or Yahweh, or “I am”. Yet, although His first disclosure was as God Almighty, or El Shaddai, He had indeed told them of this Name that now Moses will make known to His people in a fuller way.

God cannot lie. Moses does not contradict Moses. Genesis and exodus come to us from Moses, as says the longest and best traditions of the Jewish people.

So we seek another explanation. I have hinted at a couple already.

• Is it possible He is talking about introductions? He did introduce Himself to the Patriarchs as God Almighty. Not so with Moses and Israel. They shall first know Him as Lord, to be obeyed, not just to be overwhelmed by.
• Is He talking about responses required? He expected the Patriarchs to trust Him as able to do anything. He expected Israel to obey Him in everything.
• One commentary places the statement in an interrogative form: by My name Jehovah was I not known to them?

But my question really was, What is the Lord’s Name? We call upon the name Jesus today as the name of the Lord. Some still know Him as El Shaddai, others see Him as the great “I AM”.

Is there one Name that covers all? He is Lord, Master, Savior, King. Probably better let it go at that for now. You take it from here.

3. Exodus 7:3. Who hardened Pharaoh’s heart? But how and why?

Can’t do better than the Apostle Paul here. God hardened it. End of discussion. Romans 9:

For the Scripture says to Pharaoh, "FOR THIS VERY PURPOSE I RAISED YOU UP, TO DEMONSTRATE MY POWER IN YOU, AND THAT MY NAME MIGHT BE PROCLAIMED THROUGHOUT THE WHOLE EARTH." So then He has mercy on whom He desires, and He hardens whom He desires.

You say, I don’t like that! You’re not alone. Again Paul:

You will say to me then, "Why does He still find fault? For who resists His will?" On the contrary, who are you, O man, who answers back to God? The thing molded will not say to the molder, "Why did you make me like this," will it?…

Knowing of the severity of God makes grace all the more amazing. All deserved to be treated like Pharaoh. All. But God has called some to Himself, and they are overwhelmed with the unfairness of that too! But God calls it “just” when He Himself pays the price for sin and decides to give you that grace. We think so backwards.

4. Exodus 7:24. What was the water “around the Nile?” Was it not also from the Nile?

Water not specifically in the Nile River at the time of the change could be used. They dug wells and discovered pools of water that perhaps had originally been “Nile” but were not Nile at present.

5. Exodus 10:21. A darkness that can be felt? Explain.

The Pulpit Commentary explains it this way:

“It [the darkness of Exodus] is rightly regarded as an aggravation of a well-known natural phenomenon - the Khamsin, or "Wind of the Desert" which commonly visits Egypt about the time of the vernal equinox, and is accompanied by an awful and weird darkness. This is caused by the dense clouds of fine sand which the wind brings with it, which intercept the sun's light, and produce a darkness beyond that of our worst fogs, and compared by some travellers to "the most gloomy night." The wind is depressing and annoying to an extreme degree. "While it lasts no man rises from his place; men and beasts hide themselves; the inhabitants of towns and villages shut themselves up in their houses, in underground apartments, or vaults." It usually blows for a space of two, or at most three, days, and sometimes with great violence, though more often with only moderate force. …”

Whether God used an aggravation of nature or some other means, the foregoing will at least give an idea of how darkness can be felt. That is, when the means of the darkness is also the means of a physical sensation of touch, how great is that darkness.

6. Exodus 12:15. Why is leaven – yeast – a forbidden substance at Passover, even to the point of excommunication?

There is no question that the most obvious answer to the question is in the text. God wanted this night to be reenacted to the fullest. And one part of the chaos of that night was the fact that the bread being prepared by Jewish mothers all over Goshen, bread which of course normally included yeast, or leaven, was not able even to get to the oven. The yeast had not done its normal function, and the bread was simply left unleavened, unbaked, unprepared. So in the future, Passover meals were to feature this very sort of bread: unleavened.

There seems to be a more serious message being communicated by this command. Leaven represents an impure addition, a decaying substance. It can actually stand for sin. God is opposed to the “mixture” in other places in the Law. Jesus told His men to beware of the “leaven of the Pharisees”, by which He meant the impure additional teachings the religious leaders had concocted over the years.

For us, the warning is still the same. How much of the church’s teaching is pure? How much has been mixed in, to our detriment?

Paul speaks to the ultimate meaning of what God was trying to tell us, in 1 Corinthians 5:7: “Get rid of the old yeast, so that you may be a new unleavened batch--as you really are.”

7. Exodus 12:38. What is meant by the term “mixed multitude” ?

Here is a clear example of why the “mixture” is so abhorred in God’s eyes. People with no true connection to the God of Moses had added themselves to the throng now leaving Egypt. Some may have been natives of the land who were fed up with the oppression of the Pharaoh. Some may have been from other nations, fugitives, refugees. Still others may have been inter-married with an Israelite and did not want to leave their spouse.

The vision of these people was limited. Definitely they wanted out, but for their own reasons. The Jews wanted out, but they also wanted to worship their own God in freedom. Moses was one of them, and God’s chosen leader for them. The mixed multitude could have no connection to this family.

So it is in the church today. Not only is the “leaven” of false teaching among us, but false people, too. These are folks who are coming along for the ride, enjoying the food and the attention and a lot of other good things church provides. But don’t ask them to do anything. Don’t ask them to bear the cross and the shame and the persecution. When the trouble comes, the mixed multitude vanishes.

This particular group of travelers will show up later in the story, leading the congregation in complaints, and stirring up the wrath of God on Israel.