Sort Recycled Plastics by Density

Use the cooling curve sheet alongside lessons on states of matter and thermal energy. The pH, soap and plastics sheets each stand alone and work as follow ups to a short demonstration.

Calculate the density of six plastic flakes, name each plastic and plan which float or sink in each tank. The directions on the page read: Read the text. Find each flake's density (mass ÷ volume) and name its plastic. Plan which flakes go into each tank and which float or sink. Then answer question 1. An answer key is included.

Yes, both. We made it for 8th grade matter, and it works the same at home or at school. At home, a student can work through it alone and then go over it with you, which shows quickly what is solid and what needs another look. In class it works as independent practice, homework or a warm-up, and you can print one copy or a full set.

At the freezing point, particles lock into place and release energy as they settle. That energy replaces the energy flowing out, so the temperature stays level until all the liquid is solid. Thermal Energy and Particles in a Cooling Curve has students read this flat part for stearic acid.

The pH scale shows how acidic or basic a solution is, from 0 to 14, with 7 as neutral. Each step is a tenfold change in hydrogen ions, so pH 3 has 100 times as many as pH 5. Acids, Bases and Neutralization Reactions practices these comparisons.

A soap molecule has a head that is attracted to water and a tail that mixes with oil. The tails push into a grease drop while the heads stay in the water, forming a micelle that rinses away. How Soap Molecules Lift Oil From Water also explains surface tension with a floating paper clip.