Properties of shapes are also called attributes: specific things that are true about shapes
Examples are:
Similar: the shapes are the same shape (including having the same angles) but may be different sizes.
Congruent: the shapes are the same shape and the same size, though one can be flipped or turned when compared to the other.
Number of sides

	Size of angle
When describing an angle		When describing a triangle
Less than 90°	acute	all 3 angles are acute
greater than 90°	obtuse	one angle is obtuse
exactly 90°	right	one angle is right

Length of sides:
Added later:
Class discussion vid

This file includes an example of each of the combinations of angle and side length properties that are possible.  There are 7 triangles.  Cut them out, and tape them into a table like this:

	acute	right	obtuse
isosceles
scalene

Check your answers here

Communication (verbal and non-verbal: non verbal communication means things like showing diagrams and pictures and modeling what to do, it doesn't mean that you have to not talk)
Collaboration (where you or students work together or discuss together to complete the task)
Inquiry (where part of what you are doing is discovering something/figuring something out)

Here's the class discussion

Line Symmetry	The shape is the same (mirror image) on both sides of a symmetry line.  The line can be horizontal, vertical or diagonal	Show line symmetry by drawing in the symmetry line
Rotational symmetry	The shape is the same after you turn it part way around (usually when you turn it upside down it looks the same)	Show rotation symmetry by drawing a dot in the center, drawing an arrow around the shape to show how much to turn it (and keep it the same), and name how far to turn it.  In higher grades we name how to turn it by an angle in degrees.  In the lower grades, we talk about half turns and quarter turns and 1/3 turns (because you turn it half or a quarter or a third of the whole way around.  A half turn is a turn of 180°

Examples:

an isosceles triangle has one line of symmetry

an equilateral triangle has 3 lines of symmetry, and it has 1/3 turn rotational symmetry

a rectangle has 2 lines of symmetry, and it has 1/2 turn rotational symmetry

 
Here's some of the class discussion on symmetry
The web site http://www.adrianbruce.com/Symmetry/10.htm has some pictures to help you understand rotational symmetry.  Telling the order of a symmetry is almost the same as telling the turn size: an order 5 rotational symmetry, is also called a 1/5 turn symmetry.

How to play:

• Get a lot of geometric shapes
• Make 2 overlapping circles (a Venn diagram)
• The rule-maker comes up with two rules: one for each circle.  Each rule has to be a property that some of the shapes have.
• The rule maker puts at least two shapes on the diagram: one that belongs in each circle
• The guessers ask where various shapes go on the diagram until they start making guesses about what the rules might be.  If a guesser thinks they know the rule, then they tell the rule maker where they think a shape should go, and the rule maker tells them if they are correct or not.
• After all the shapes are on the diagram (some shapes belong in circles, and some shapes belong outside both circles), then someone guesses what they think the rule is. 
  

Here is our class playing the guess my rule game
Here is a third grade class doing a very similar activity: http://www.learner.org/courses/learningmath/geometry/session10/35video.html