Still new to chess. May I ask why this queen a4 check is considered a mistake?

Yes, after he defends the check with his bishop, he will have a developed bishop and you will have lost time.

Time is as valuable as material in some situations.

Basically you just gave away white's first move advantage.  Tempo is a crucial element of chess and you do not want to move the same piece twice in the opening unless you have a very good reason.  Giving check accomplished nothing here but allowing your opponent to develop.  Better moves would have been Nc3, Nf3, or even e3.  It's OK, beginners love to move their Q out early and love to give check, so you're just doing what most beginners would have probably done.  I'm sure you'll get the hang of this whole "development" thing with a few more games experience.  Good luck!

Thanks guys for your insights. Will keep learning from these mistakes and learn not to repeat them in future games.

I recommend you to buy (download) a chess book for beginners. In a book for beginners everything should be structured in a system. And if you don't want to make a research - buy a premium membership and do lessons. You need a system to develop your skill.

You end up with exactly the same position of the White pieces as if you played Qc2 in the first place, but Black's bishop is now on d7 instead of c8.  If the bishop is better on d7, you helped Black out.

In general these checks are worthwhile if the king has to move, or the piece that blocks is forced to a square it doesn't want to be on, or you can follow up with an attack on the blocking piece.  None of those apply here.

You are giving away white's precious tempo. However, it black plays 2... dxc4 then 3. Qa4+ is a viable way to win the pawn back.

Play slow time controls, and use this guide to help you decide on moves.

Opening Principles:

1. Control the center squares – d4-e4-d5-e5
2. Develop your minor pieces toward the center – piece activity is the key
3. Castle
4. Connect your rooks

Tactics...tactics...tactics...

The objective of development is about improving the value of your pieces by increasing the importance of their roles. Well-developed pieces have more fire-power than undeveloped pieces and they do more in helping you gain control.

Now we will look at 5 practical things you can do to help you achieve your development objective.

They are:

1. Give priority to your least active pieces.

• Which piece needs to be developed (which piece is the least active)
• Where should it go (where can its role be maximized)

2. Exchange your least active pieces for your opponent’s active pieces.
3. Restrict the development of your opponent’s pieces.
4. Neutralize your opponent’s best piece.
5. Secure strong squares for your pieces.

Don’t help your opponent develop.

There are 2 common mistakes whereby you will simply be helping your opponent to develop:

1. Making a weak threat that can easily be blocked
2. Making an exchange that helps your opponent to develop a piece

Pre Move Checklist:

1. Make sure all your pieces are safe.
2. Look for forcing moves: Checks, captures, threats. You want to look at ALL forcing moves (even the bad ones) as this will force you look at, and see the entire board.
3. If there are no forcing moves, you then want to remove any of your opponent’s pieces from your side of the board.
4. If your opponent doesn’t have any of his pieces on your side of the board, then you want to improve the position of your least active piece.
5. After each move by your opponent, ask yourself: "What is my opponent trying to do?"

now that's what a chess community is all about ! well replied you lot  you do cc proud

You also get 1 free lesson a day here. I don't think they advertise this enough. 1 lesson a day is quite enough. I take about a couple of days, to months, with just one lesson, depending on how difficult the concepts introduced in it are.

I guess that's another reason why players cherish those single lessons they get from their icons and famous chess players, a single lesson can last an entire lifetime. That's because they take a lifetime to master.

This is the best run down of chess strategy I have seen in one place on this site so thanks very much to all the contributors in this thread.

As IMBacon says:

Don’t help your opponent develop.

There are 2 common mistakes whereby you will simply be helping your opponent to develop:

1. Making a weak threat that can easily be blocked