Grade 7 Chemistry and Physics: Matter, Waves, and Laboratory Safety

Flashcards covering states of matter, mixtures, pure substances, wave properties, and laboratory safety/equipment based on the Grade 7 Chemistry and Physics notes.

Matter

Anything that has mass and occupies space.

Solid

A state of matter with a fixed shape and volume where particles vibrate in place and are not easily compressed.

Liquid

A state of matter with a fixed volume that takes the container shape; particles slide past each other and are only slightly compressed.

Gas

A state of matter with no fixed shape or volume where particles move freely and are easily compressed.

Plasma

The fourth state of matter formed when gases become extremely hot and particles break apart into charged particles.

Pure Substances

Substances made of one type of particle with a constant composition that cannot be separated physically.

Element

A pure substance made of one kind of atom only, such as Helium ($He$) or Oxygen ($O_2$).

Compound

A pure substance made of two or more different kinds of atoms chemically combined, such as Water ($H_2O$).

Mixtures

Combinations of two or more substances that are not chemically combined and can be separated physically.

Homogeneous Mixture

A mixture that looks the same throughout with uniform composition and identical properties; also called a solution.

Heterogeneous Mixture

A mixture that has more than one phase where each component exhibits its both physical and chemical properties.

Wave

A disturbance that transfers energy from one place to another without moving matter.

Mechanical Waves

Waves that require a medium (solid, liquid, or gas) to travel and cannot travel in a vacuum.

Electromagnetic Waves

Waves that do not need a medium and can travel through empty space, such as visible light or X-rays.

Transverse Waves

Waves where the motion is perpendicular to the direction the wave travels.

Crest

The highest point of a transverse wave.

Trough

The lowest point of a transverse wave.

Amplitude

The distance from the rest position to the crest or trough; a larger value indicates more energy.

Longitudinal Waves

Waves that travel in the same direction (parallel) as the vibrations that produce them.

Compression

The part of a longitudinal wave where the particles are close together.

Rarefaction

The part of a longitudinal wave where the particles are spread apart.

Surface Waves

A combination of transverse and longitudinal waves where particles move in circular paths, such as ocean waves.

Wavelength ($\lambda$)

The distance between repeating parts of a wave, such as from crest to crest or compression to compression.

Frequency ($f$)

The number of waves passing a point in $1\,\text{second}$, measured in Hertz ($Hz$).

Period

The time taken by one wave to pass, measured in seconds ($s$) and defined as the inverse of frequency ($P = \frac{1}{f}$).

Corrosive substance ($C$)

A substance that attacks living tissues.

Combusting agent ($Q$)

A material that can provoke the burning of combustible substances.

Decantation

A separation technique involving carefully pouring off the top liquid layer while leaving the sediment behind.

Centrifugation

A method that separates parts of a mixture based on density by spinning it very fast, causing denser parts to sink.

Separatory funnel

Laboratory glassware used to separate heterogeneous liquid mixtures that are immiscible.

Mortar and pestle

Laboratory equipment used to crush and grind chemicals into powder.

Condenser

Glassware used in the process of distillation for condensation.