In Macbeth, what are examples of where the reality of a situation is hidden by outward appearances in Act 1?
An example is "False face must hide what the false heart doth know." Deceptive appearances are a recurrent theme in the play.
You have certainly put your finger on a key theme in this play. From the first scene of Act I, when the witches say what could be called the motto of the play ("Fair is foul and foul is fair"), deception and the gap between appearance and reality is key, as this motto points towards a world where everything is not what it actually seems. Act I contains many examples you could look at, but to me the character to focus on is Lady Macbeth. Note how she counsels her husband in Act I scene 5:
Your face, my Thane, is a book, where men
May read strange matters. To beguile the time,
Look like the time; bear welcome in your eye,
Your hand, your tongue: look like th'innocent flower,
But be the serpent under't.
Here she says to Macbeth that he is too readable - others can read his intentions like a book. The final simile captures most clearly the theme you have identified. Therefore Lady Macbeth counsels her husband to act like an "innocent flower" that draws people in, whilst all the time secretly being the poisonous viper that lurks beneath it waiting to jump out and kill the prey that it attracts.
In case Macbeth didn't get the message, Lady Macbeth provides an excellent example for us in scene 6, where she welcomes Duncan to her home whilst at the same time knowing that he will never leave there again:
All our service,
In every point twice done, and then done double,
Were poor and single business, to contend
Against those honours deep and broad, wherewith
Your Majesty loads our house...
She plays the part of an excellent hostess, whilst secretly plotting the murder of her guest.
Hope this helps - now re-read the first Act and look for some more! Good luck!
Shakespeare's Macbeth is a play which has, as you mention, the consistent theme of deceptive appearances. The first indicaton that all is not as it appears can be found in the first scene of the play, a short meeting between the witches. They speak this line together:
"Fair is foul, and foul is fair."
The last words in Act I are spoken by Macbeth after he has purposed to murder Duncan:
In between are the following deceptions:
- Macbeth is a loyal soldier who plots, along with his wife, to kill the king.
- The Macbeths act as gracious hosts for a man they plan to kill.
- Macbeth originally says he's just going to let the predictions unfold as they will; later he says Malcolm being named successor to the throne is a step he must "o'erleap" if he is to be king.
- Macbeth laughs and jokes around with Banquo after the predictions are made; however, after he is named Thane of Cowdor, he takes them quite seriously.
- What Macbeth says out loud is not what he says in his asides to the audience.
- Lady MAcbeth appears to be a loving wife and hostess; beyond that, she is cruel and manipulative in order to get her way.
These are just a few instances of hidden motivations behind false fronts which we see early in the play. From beginning to end, Act I of Macbeth is full of things which are not as they appear to be.