Great Grams and Grahams

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Objective

SWBAT solve problems involving masses of objects and use grams and kilograms to measure the mass of objects.

Big Idea

In this lesson students use grams to measure the mass of graham crackers. Students work with partners to weigh objects as well as solve various word problems.

Number Hook

7 minutes

This is a very fun game that students love playing. I start by telling them that I know a game I can always win. I ask them if they want to play it with me.  Fourth graders usually think they can beat me as soon as I tell them I always win!  I introduce the game of Rotten Apple.  To play the game, I draw 13 circles on the board. These are the apples. The object of the game is to NOT be the person that gets the LAST apple, IT'S ROTTEN!  On a turn, a player may cross out 1 or 2 apples until there is only one last apple left.

I play several rounds with the students, winning of course!  I challenge students to come up with a winning strategy.  If students come up with a strategy that will allow them to win every time, I give extra credit points. In the past, I've had many students find the winning strategy because they go home and play it multiple times in order to manipulate the numbers and situation.

Click here to access directions to this game.  This game is also known as Nim or Poison.

Note:  To win this game, students must figure out that the numbers 10, 7, 4 and 1 are important.  To win, a player must keep track of the number of apples crossed out.  If the player crosses out the above numbers, they will win!

Concept Development

50 minutes

In this lesson, students use grams to measure the weight of graham crackers and various school objects. The distinction between mass and weight is not made until middle school, when students begin their study of gravity. Therefore, the emphasis of this unit should be placed on measurement.

In the classroom, I try to use the correct name (mass or weight) depending of the instrument used to make the measurement. (“Mass” is used when measuring with a balance scale; “weight” is used when measuring with a spring scale, which includes scales like a bathroom scale.) The correct term for this task is mass because students are using a balance scale.

To introduce this lesson, I show a gram weight. I tell students it's name and the symbol and describe it as a standard unit of weight in the metric system.

I then use the balance scale to compare 1 gram (1g) to a large paper clip. I show the other gram weights (5g, 10g, and 20g) and have students estimate how many paper clips would equal each weight. I ask students to share their findings.

Next, I give every student one half of a graham cracker (2 rectangles). I ask students to close their eyes and to concentrate on feeling the graham cracker, thinking about how light or heavy it is.  I then let students eat their graham crackers so they are not tempted to eat the cracker they will use on their balance scales.

Then, I instruct students to place one graham cracker on the scale and ask them to estimate how many grams the cracker is.  Students then use the scales to find the mass of one graham cracker.

I ask students to find the mass of their pencils, a banana, an apple, and a dry erase marker.  Students will find the mass of each object using gram weights. They record the mass in a chart.

You can see in this video, students using the balance scale to find mass.

You can see in this video the amount of mental math this lesson also used.  Students work together to find total amounts of grams.

When most students are done finding the mass of the items, I lead a brief discussion about the results.  Students realize that if the graham cracker was broken in different places, that could account for different gram measurements.  Students were very close in all measurements and we talked about the balance scales we were using and how difficult or challenging it can be to observe if the pans are level or equal.