Investigating Mixtures

1. Classifying Matter Using Physical Properties

Physical properties are things you can see, feel, or measure about an object without changing what it is made of. We use these traits to describe, group, and identify different kinds of matter.

• Properties You Can See and Feel: Traits you observe using your five senses.

  • Color and Luster: How something looks, such as bright red, or shiny like metal versus dull like cardboard.

  • Texture: How a surface feels when you touch it (e.g., smooth, rough, soft, or sticky).

  • Shape and State of Matter: Tells us if an object is a solid, liquid, or gas, and what shape it has.

• Properties You Can Measure: Traits measured with tools like rulers or scales.

  • Size, Mass, and Volume: Show how big an object is, how much space it takes up, and how heavy it is.

  • Density: Helps show if an object will sink or float based on how tightly packed its parts are.

2. Changes in Physical Properties

A physical change changes how an object looks, its size, or its state, but it stays the same substance on the inside.

• Phase Changes (Changes of State): Happen when things heat up or cool down.

  • Melting: Adding heat turns a solid into a liquid (like ice turning into water).

  • Freezing: Taking away heat turns a liquid into a solid (like water turning into ice).

  • Evaporation: Heating a liquid turns it into a gas (like water turning into steam).

  • Condensation: Cooling a gas turns it into a liquid (like water drops forming on a cold glass).

• Shape and Size Changes: Actions like cutting, tearing, crushing, or bending change what an object looks like, but not what it is made of.

3. Physical Properties in Mixtures

A mixture is made when you mix two or more things together. The way physical properties behave depends on how the materials mix:

• Mixtures:

  • The materials keep their own physical properties.

  • In mixtures like trail mix or sand in water, each part keeps its own color and shape, so you can easily separate them.

• Solutions:

  • One substance dissolves and spreads evenly through another.

  • Even if a solid like salt seems to disappear in water, it is still there (you can still taste the salt).

  • You can separate the parts physically, like boiling away the water to leave the salt behind.