Grade 3 - the 8-year-old
The subject of different kinds of animals is expanded this year to include the terms of vertebrates and invertebrates. They should also have learned about warm-blooded and cold-blooded animals if you haven’t covered these subjects yet. The major characteristics of animals should have been learned by now. A much more detailed study of diet and nutrition is also covered during this year (sugars, starches, fats, proteins, minerals and vitamins). Their knowledge of the earth science and space science themes should also be expanded as can see in the chapter topics listed below. Several of the topics below have been suggested already in comments I have made above.
Heath Science 3
Unit 1 - Investigating Living Things and Environments
Chapter 1 - Where Do Plants and Animals Live?
A Wet, Dark Place - Earthworms
A Hot, Dry Place - the Desert
Habitat
Migration and Fly-ways
Chapter 2 - Groups of Living Things
Populations
How Populations Grow
How Seeds are Transported
How Populations Live and Work - Beavers and Dams, Bees and Ants
How a Population Gets Smaller
Chapter 3 - A Community
Habitat = Community
Food and Energy
Plants and Water
Soil Makers, Decomposers, Molds and Mosses
Animal Eaters (Carnivores) and Plant Eaters (Herbivores)
A Food Chain
Staying Alive in a Community - Predators, Protective Measures, Camouflage
Changes in a Community
Unit 2 - Investigating the Earth and the Universe
Chapter 4 - Water Cycle
Water in the Air - Water Vapor, Dew
Making Clouds
Fog, Rain, Sleet, Snow
Water in the Ground
Water on the Ground
The Water Cycle
Storing Water, Dams, Electrical Energy
The Need for Clean Water
Chapter 5 - The Changing Land
Mountains and Weathering
Moving Water Changes the Land, Erosion
Moving Ice Changes the Land
Building the Land
Mountains, Volcanoes (Crust, Lava)
Chapter 6 - Stars
Stars - How Hot?
Our Closest Star
Light and heat from the sun
Star pictures - Constellations
Circumpolar Constellations
Milky Way - Galaxy
Telescopes
Unit 3 - Investigating Machines and Energy
Chapter 7 - Machines at Work
Lifting Things - Muscles, Levers
Wheels with Teeth - Gears
Ramps
Splitting Things - Wedge
Chapter 8 - Using Electricity
Electric Current, Dry Cell, Circuit
Electric Current into Light and Heat
Electric Current Moves Objects - Electromagnet
Electricity at Work
Saving Electrical Energy
The Safe Thing to Do
Unit 4 - Investigating Nutrition and the Human Body
Chapter 9 - How Do We Eat?
Sugars
Starches
Fats
Proteins
Minerals and Vitamins
A Diet
Chapter 10 - How We Use What We Eat
Where Digestion Begins: The Teeth
More Digestion in the Mouth - Saliva
The Food Tube (esophagus) and Stomach
The Small Intestine
The Large Intestine