Purchase a few stethoscopes for the children to use in the classroom. Ask children to choose a buddy to work with, and give each pair of students a stethoscope to explore. Show children how to locate the heart, and remind them that to hear the heart they must remain very quiet. Allow children to take turns listening to the heart of their partners. Ask children to listen closely and tap out the rhythm of their partner's heartbeat on a table or other hard surface with their fingertips.
Explain to the children that while their body is at rest their heart will beat slowly and evenly. When exercising, their hearts must work a little bit harder to carry blood and oxygen to other parts of their bodies, causing their hearts to beat faster. Split your class into pairs again and assign each pair a stethoscope. Have one child sit while the other child listens to his heart. Then, ask the children to do 10 jumping jacks and listen to the heart again. Have children tap out the rhythm of the heartbeat before and after the jumping jacks. Compare the rhythms or count the beats to improve understanding.
This science activity works best when children work in pairs of two. Give each child a large sheet of butcher paper and ask her to trace the outline of her partner's body. Allow each child to draw her face on her own model. Use an online resource to find templates for several major organs in the body such as the heart, stomach, lungs and brain. Allow children to color and cut out these major organs and attach them to their life-size model using a glue stick.
Use your large group circle time to discuss with children the difference between healthy and unhealthy foods. Explain to children that eating healthy snacks is important for their hearts, brains and growing muscles and bones. Using old cooking magazines, find pictures of healthy and unhealthy snacks for children to cut out. Create a large poster showing healthy versus unhealthy snacks by gluing the pictures to a poster board. Display the poster near the snack preparation area, and allow children to refer to it when planning the snack menu.