Sixth Grade Science

Physical Change A physical change is a type of change that does not change what the substance is. If you put a cup of water in the freezer, the liquid water turns to ice. Is the ice still water? Yes! Ice is water in solid state. You can melt ice and get liquid water back. When you tear a paper into pieces, each piece is still made up of the same material as the whole piece of paper. The pieces are still paper.

Physical Change Examples Ice melting (just changes form) Blowing a dandelion (just changes location) Chocolate bar melts (just changes shape) Glass broken (just changes shape/size) Rock weathers into pebbles (just changes shape/size) Making chocolate milk (just changes color, can be separated)

Chemical Change During a chemical change, substances are changed into different substances. A chemical change not only alters the substance’s physical properties, but actually changes it into something new.

Signs of a Chemical Change Color changes When leaves change color in the fall When an apple turns brown after it’s been left out

Signs of a Chemical Change Energy is released or absorbed: light or temperature Fireworks release energy as light During cooking, like baking a cake, energy as heat is absorbed

Signs of a Chemical Change Change in odor Spoiled food smells bad!

Signs of a Chemical Change Production of gases or solids The bubbles of gas that you observed form when an antacid is dropped into water A solid that separates out is called a precipitate

Signs of a Chemical Change Not easily reversed After wood burns, ash cannot be made into wood again

Important In a physical change, the composition of a substance DOES NOT CHANGE. However, in a chemical change, the composition of a substance DOES CHANGE.

Chemical Change Examples Baking a cake (change in color, change in temperature) Striking a match (energy released as light and heat) Bleaching hair (change in color, change in odor) Garbage rotting (change in temperature, change in odor) Bicycle rusting (change in color) Plants making oxygen (energy (sunlight) is absorbed, new gas forms)

Law of the Conservation of Mass The mass of what you end with is always equal to the mass of what you start with. Example: Baking a cake—If you measured the mass of the batter, and then measured the mass of the cake after it was baked, they would be the same! Mass is not destroyed or created during chemical reaction, just changed.

Brain Pop Video Property Changes

Physical or Chemical Change? Milk is warmed up. Water is heated and changed to steam. Iron rusts. Ice melting. Milk sours. Sugar dissolves in water. Wood rotting.

Physical or Chemical Change? Pancakes cooking on a griddle. A tire is inflated with air. Food is digested in the stomach. Water is absorbed by a paper towel. A glass is broken. A pot of water is boiling. Dough is baked into a cake.

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