# Science 6 reference sheet

## Inquiry
- Change one variable, measure another, and keep important conditions comparable in a fair test.
- Record units, repeated trials, source context, possible error, and method improvements.
- Distinguish observations from explanations.

## Body systems
- Excretory: kidneys → ureters → bladder → urethra.
- Hormonal: glands release chemical messengers that act on target cells.
- Nervous: receptor → sensory signal → brain/spinal cord processing → motor response.
- Reproductive: major organs produce reproductive cells/hormones and, in female anatomy, support pregnancy.

## Mixtures
- Suspension: dispersed particles may settle.
- Emulsion: droplets of one liquid dispersed in another.
- Colloid: small dispersed particles/droplets remain distributed for long periods.
- Separation must exploit a property difference such as particle size or density.

## Forces
- Newton 1: without an unbalanced external force, velocity does not change.
- Newton 2 (Grade 6 qualitative): an unbalanced force causes acceleration.
- Newton 3: interaction forces are equal in size, opposite in direction, and act on different objects.
- Gravity is an attractive force; near Earth it points approximately toward Earth’s centre.

## Space
- Earth ⊂ solar system ⊂ Milky Way ⊂ observable universe.
- Universe age: approximately 13.8 textbillion years.
- Rotation = spin about an axis; revolution = motion around another body.

Always state what a model represents, what evidence supports it, and what it leaves out.
