Physical Science
Physical Science on the Grade 5 OST tests matter, changes, and energy transfer. Expect questions on properties, conservation of mass, mixtures, and how light and sound behave.
Core rules and concepts
- Matter has mass and takes up space. Mass is conserved in a closed container during physical and chemical changes; gases still have mass.
- Physical changes alter form, size, or state but not the identity of the substance, such as ice melting or sugar dissolving. Chemical changes form a new substance, often with evidence such as gas, color change, heat, or precipitate.
- Mixtures combine substances that keep their properties and can often be separated physically; compounds are chemically joined.
- Light travels in straight lines until it strikes a surface. It can reflect, refract when changing medium, or be absorbed.
- Sound is a vibration that needs a medium. It travels through solids, liquids, and gases but not a vacuum. Higher frequency means higher pitch; greater amplitude means louder sound.
- White light contains a spectrum of colors; objects appear a color because they reflect that color and absorb others.
Worked example
A straw in a glass of water looks bent at the surface. Reasoning: light from the straw passes from water into air and changes speed, so it refracts at the boundary. Your eye traces the light backward in a straight line, making the straw appear displaced. The straw is not actually broken.
Traps that cost marks
- Saying gas has no mass or that dissolving is always chemical.
- Thinking sound can travel through empty space.
- Confusing pitch, which is frequency, with volume, which is amplitude.
- Claiming white light has no colors or that a red object adds red light.