Ask your child what happens if you put an egg in a tall glass filled with water. You can test what happens by carefully immersing an egg in a half-filled glass of water; the egg sinks.
Stir about 6 tablespoons of salt into a glass half-filled with water and then top it with plain water. Do not stir the water or mix the two layers. Lower the egg, and watch it float in the middle of the glass. The added salt makes that water dense, so the egg can float
Food science experiments are fun and engaging. Turning an everyday product into an experiment sends the message that you can observe science at the breakfast table or in the fridge. The surface tension of differ liquids varies. If you add detergent to milk, you lower the surface tension. For this fun and colorful experiment use full fat milk or buttermilk for best effect. You also need food coloring, cotton swabs and dishwashing detergent. Pour milk onto a plate and spread out three or four drops of food coloring. Put the cotton on the middle of the plate - nothing happens. Dip the cotton swab in dishwashing liquid and watch the colors swirl around. The dishwashing liquid reacts with the milk and sets the milk into motion.
Oil and water do not mix and you can use this to make a lava lamp. Oil is lighter than water and it floats on water. Use clear soda bottle, water, oil, fizzing tablets and food coloring. Fill the bottle with water and use a cup or funnel to pour in oil. Wait until the oil and water has separated and add a couple of drop of food coloring. Add half a fizzing tablet, and watch the colorful bubbles swirl around in the bottle.
Earth science studies the conditions inside our earth. They take samples by drilling into the core of the earth; they also drill into mountains and ice to determine what the weather conditions were like thousands of years ago. A fun way to take your own samples is to use a thick straw and insert it into different kinds of cupcakes and cakes. Use cakes with interesting colors, sprinkles, and frosting to get more varied samples.