Classifying Matter
Physical properties of matter can be observed, tested, or measured. Mass, relative density, solubility, physical state, magnetism, electrical conductivity, and thermal conductivity are physical properties.
Mass is how much matter is in an object. You can measure mass using a balance. Mass is measured in milligrams, grams, and kilograms.
Objects with more mass are heavier. For example, a boulder has more mass than a pebble. A pencil box that is full of supplies has more mass than an empty pencil box.
Objects with less density float better than objects with more density. Many pool toys are designed to either sink or float. You may want to lounge in the water on a pool float. The pool float is less dense than water. You may want to dive for heavy sticks that are designed to sink in water. The sticks are denser than water.
A substance is soluble in water if it can be dissolved completely in water. When a substance dissolves, it gets smaller and smaller until it can no longer be seen. The substance is still there; you just can’t always see it.
For example, you can dissolve sugar in water. Sugar is soluble in water.
Some substances, like sand, are insoluble, meaning they do not dissolve in water.
Matter on Earth can be found in three different physical states: solid, liquid, or gas.
Solids have a fixed volume and shape that does not change. Liquids keep their same volume, but their shape changes depending on its container. Gases have no fixed shape or volume.
Some matter, like nickel, iron, cobalt, and steel, is attracted to a magnet. Objects attracted to a magnet are magnetic and objects not attracted to a magnet are non-magnetic.
Electrical current flows in a circle from a power source to the object it is powering. Objects are either conductors or insulators of electricity.
Conductors allow energy to flow through. Insulators do not allow energy to flow through.
Electrical wires are often made of copper, a good conductor of electricity. Copper allows electricity to flow through easily. Electrical wires are usually coated with an insulator.
Thermal conductivity refers to how well matter allows heat to pass through. Like with electrical energy, matter can be a thermal conductor or a thermal insulator. Metal is a good thermal conductor. Styrofoam, air, and cotton are good insulators.