Science Chapter 6 & 7: Matter and Mixtures

Chapter 6: Particles and States of Matter

• Three states of matter exist: solids, liquids, and gases
• Matter changes state when heat energy is added or removed
• Water exists as ice (solid), liquid water (liquid), and water vapor (gas)
• Particles are arranged differently in each state, affecting their properties
• Solids: Particles are closely packed in a regular pattern, have very little space between them, and vibrate in place. They maintain their shape.
• Liquids: Particles are closely packed but have no regular pattern; particles are free to flow past each other. They take the shape of their container.
• Gases: Particles are far apart with no regular arrangement; particles move freely in all directions. They will completely fill the container they are in.

Chapter 7: Mixtures

• A mixture is formed when two or more substances are mixed together.
• The properties of each substance in the mixture are not changed.
• Mixtures can be separated using physical methods.
• Three types of mixtures were described:
  • Solid-Solid (e.g., sand and salt)
  • Solid-Liquid (e.g., sand and water)
  • Liquid-Liquid (e.g., rat poison and human poison)
• Methods for separating mixtures include:
  • Hand Sorting: Separating solids that are large enough to be picked by hand
  • Sieving: Separating solids of different sizes using a sieve
  • Settling: Allowing heavier solids to settle to the bottom of a liquid mixture, so the liquid can be poured off.
  • Decanting: Carefully pouring off a liquid from a mixture, leaving the solid behind
  • Filtering: Separating a solid from a liquid by using a filter. The solid is trapped on the filter, and the liquid passes through. (e.g., coffee and water)
  • Winnowing: Separating lighter material from heavier material by blowing the lighter material away (e.g., grain from chaff).

Chapter 8: Solutions

• A solution is a mixture of two or more substances, where one substance (the solute) is dissolved in another (the solvent), usually a liquid.
• After mixing, the solute is not visible.
• Soluble: Describes substances that can dissolve in a liquid
• Solvent: The liquid in which something dissolves
• Solute: The substance which dissolves in the liquid
• Solution: A combination of the solute and solvent
• Particles of the solute disperse into the spaces between solvent particles when dissolving and do not settle out.
• Saturated solution: A solution in which no more solute can dissolve at a given temperature. Extra solute will settle out.
• Insoluble substances: Substances that do not dissolve in a given liquid.

Chapter 9: Dissolving

• The rate of dissolving is the speed at which a substance dissolves.
• Factors that affect the rate of dissolving include:
  • Temperature (higher temperature = faster dissolving)
  • Stirring (more stirring = faster dissolving)
  • Grain size (smaller grains dissolve faster)
• Graphs are used to show the relationship between variables.

Chapter 10: Mixtures and Water Resources

• Water is a vital resource used in many industries and by all living things.
• Pollutants are harmful substances that are introduced into the environment.
• Pollutants can affect entire ecosystems.
• Water is a solvent that contributes to the environment.
• Soluble pollutants dissolve in water, while insoluble pollutants float or sink.
• Wetlands are important ecosystems where land and water meet.

Chapter 11: Processes to Purify Water

• Water is essential for life.
• Humans, plants, and animals require clean water.
• Water can be purified through boiling and by adding chlorine.

Chapter 16: The Solar System

• The Sun is at the center of the solar system.
• The Sun is a star made of hot gas.
• Planets orbit the sun.
• Planets have different sizes and compositions.
• Planets take different amounts of time to orbit the sun.
• Inner planets are rocky, while outer planets are made mostly of gas or ice.
• An asteroid belt separates inner and outer planets.
• Moons orbit planets.

Chapter 17: Movements of the Earth and Planets

• Planets orbit the Sun and also rotate on their own axis.
• Rotation on an axis causes day and night.
• The Earth's movement around the sun is called revolution.
• The time it takes a planet to orbit the sun is determined by its distance from the Sun.

Chapter 18: Movement of the Moon

• The Moon rotates on its own axis and orbits Earth.
• The Moon takes the same amount of time to rotate as it does to orbit Earth, so we always see the same side of the moon.

Chapter 19: Systems for Looking into Space

• Telescopes are used to study objects in space.
• There are two types of telescopes: optical and radio.
• Optical telescopes use mirrors and lenses to catch light.
• Radio telescopes use large dishes to collect radio waves.
• The Southern African Large Telescope (SALT) and the MeerKAT radio telescope are large telescopes located in South Africa.

Chapter 20: Rovers

• Rovers are vehicles used to explore other planets.
• Some rovers explored the Moon, and others, like the Curiosity rover, have explored Mars.
• Rovers need specific design features to operate in the harsh conditions of space.

Chapter 12: Electrical Circuits

• Electricity is a form of energy.
• Electrical energy flows through circuits which need a source (like a battery), a process (the components that change electrical energy into another type), and devices to use the energy.
• A circuit needs to be complete (no breaks) for the current to flow.
• Switches are used to turn circuits on and off in electrical devices.

Chapter 13: Electrical Conductors and Insulators

• Conductors allow electricity to flow through them easily (e.g., metals)
• Insulators resist the flow of electricity (e.g., plastics, rubber, glass).
• Insulators are used to protect people from dangerous electrical shocks.