Ask the students if they know about the primary colours, red, yellow, and blue. Tell them that mixing the primary colours can create other colours. This can be demonstrated by mixing yellow and blue acrylic paint to get green.
Problem: “Picasso has three recipes for mixing green paint. They are:
A: One part of blue with three parts of yellow (1:3)
B: Four parts of blue with eight parts of yellow (4:8)
C: Three parts of blue with five parts of yellow (3:5)
Which recipe will give him the darkest shade of green?” (It is the relative quantity of blue to yellow that makes the green darker.)
Get the students to build Unifix cube or beans models of the three recipes:
Ask the students how the different ratios could be compared. Their responses might
(i) Relating the recipes to equivalent fractions, e.g., 1:3 is the same as 1/4 , 4:8 is the same as 4/12 = 1/3 , 3:5 is the same as 3/8 .
(ii) Equalising the lengths of the cube models by building up or breaking down, for example, 1:3 makes up to 6:18 (six times), which is a smaller ratio than 4:8, which makes up to 8:16 (two times). Both stacks have 24 cubes.
(iii) Mapping one of blue onto so many yellows, for example, 3:5 means that one blue is mapped onto one and two-thirds yellows (1:1 2/3), 4:8 means that one blue is mapped to two yellows (1:2).
Considering method (ii), the students might make duplicates of the recipes until the lengths are equalised. The yellows and blues are then collected so that the ratios can be compared.
This is easily drawn on a double number line:
Challenge the students to represent each ratio using the rotating region. This provides an excellent link to percentages as each circle has one hundred divisions around its circumference.
These circles can be rotated to show any two fractions that add to one. Pose similar problems for the students to explore using cubes or beans.
Recipes for orange:
X: 3 parts red to 7 parts yellow (3:7 or 3/10)
Y: 5 parts red to 15 parts yellow (5:15 or 5/20)
Z: 1 parts red to 4 parts yellow (1:4 or 1/5)
“Which recipe gives the darkest orange?” (It is the relative quantity of red to yellow that makes the colour darker.)
Shielding: Pose problems that make comparison easy. For each recipe, make a stack with cubes. Trace around each length of cubes and mark and shade the colour break.
Ensure that the ratios are recorded so that the students can refer to them.
Problem: Recipe for purple:
P: 6 parts red with 14 parts blue
Q: 4 parts red with 6 parts blue
R: 7 parts red with 8 parts blue
“Which recipe gives the darkest purple?” (It is the relative quantity of blue to red that makes the colour darker.)
Using Number Properties
Pose problems of ratio comparison using only numbers. Record these problems using symbols:
“Which blue-to-yellow ratio gives a darker shade of green?
2:5 or 3:4 7:15 or 3:6 1:4 or 18:80 4:7 or 9:18 7:8 or 8:9”
(Note: Once again, it is the quantity of blue that determines the darkness of the colour.)
The students will need to consider these ratios as proportions, for example, 2:5 is equivalent to 2/7.
Angela President Chicago Public School
1819 Pershing Road
Chicago IL 60609
The objective of this lesson is for pre-schoolers and primary
graders to learn about mixing colors by light beams. The enjoyment of seeing
the colors change and learning the difference from mixing paints.
These materials are for the teacher to give the lesson.
Three Projectors or some source of light to project the
different colors of mylar paper
A color template
Three pieces of mylar paper, green, blue and red
Three small or medium size mirrors
An overhead projector
To begin this lesson the teacher is to give a homework
assignment the night before. The homework assignment is for the children to go
home and look at their color television screen. While looking at the T.V. move
very close to it and see what colors they see.
When they return the next morning, you ask who did their
homework. Those children are to tell you what colors they saw. The teacher
then explains that they are going to mix colors of light today.
You begin by placing your three color template on the overhead
projector. Turn the overhead projector on, then turn it around so the light
beams are toward the back of the class. Now you will ask three students to help
find the light beams with the mirrors. When they find them, ask that they put
them on the front wall or screen if you have one. Now you ask them "If you mix
red and blue together what will you get?", they will say purple. Then you ask
the children who have red and blue to put their light beams together. Then ask
"What if green and red were mixed together, what color would you get?" As you
ask the questions you are mixing the lightbeams. Give the children a chance to
try to mix them on their own and take turns. You are also to mix all colors
together in different ways.
RED and GREEN MAKE YELLOW
BLUE and RED MAKE PURPLE
BLUE and GREEN MAKE BLUE-GREEN OR AQUA
RED, BLUE and GREEN MAKE WHITE YES WHITE Discuss colors, color mixing by addition is the mixing of light of different frequencies. Performance Assessment:
I have made this simple for primary children. They will
enjoy seeing the lights and colors. This lesson can be used for upper grades if
you add a more difficult task. You can also have the children work with paints
and learn the difference by working with different colors.
1. The amazement of this lesson is due to the way the human eye works.
2. Note, the primary colors of light are different than the primary colors of
Ms. Ann Brandon, my mentor in S.M.I.L.E. Physics
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