Unit 7 MATTER AND FORCES SUMMARY

Everything in the Universe is made up of matter

MATTER

It is the amount of matter in an object. We measure it in grams (g). 1000 grams = 1 kilogram

Properties

Color, odor and taste

Matter is made up of atoms.

Molecules are groups of atoms

Hardness

Density

Mass

Volume

Solubility

It describes how much space matter occupies. It is measured in mililiters (ml). 1000 ml = 1 litre

It is the amount of matter in a volume. We measure density in kilograms per litre (kg/l). Density = mass/volume. It explains why some objects float in water while others sink.

When a solid object is in a liquid…

… it will float if its density is lower than the density of the liquid.

… it will sink if its density is higher than the density of the liquid.

It is the scratch-resistance of a solid. Diamonds are the hardest natural solids.

It is the ability of a substance to dissolve in other substance and form a solution. Ex. Sugar dissolves well in water, whereas oil does not.

Thermal conductivity

It is the ability of certain substances to conduct or transfer heat. Metals, such as iron or copper, are good heat conductors, while materials such as wool, wood, paper, plastic or glass are good heat insulators.

Unit 7 MATTER AND FORCES SUMMARY

TYPES OF MATTER

Pure substances

Heterogeneous mixtures: you can see the different components (salad, rocks…)

They consist of just one type of matter. For example: gold, iron, salt, sugar, minerals.

Substances in a mixture can be separated using different methods

Filtration is the operation used for the separation of solids from fluids by interposing a medium through which only the fluid can pass. Oversize solids in the fluid are retained

Sieving We can use a sieve to separate solids of different sizes, such as pebbles from sand.

Evaporation is a type of vaporization of a liquid that occurs only in the surface of a liquid.

Mixtures They consist of two or more types of matter.

Homogeneous mixtures: you cannot see the different components (seawater, air…)

Alloys are another type of homogeneous mixtures in which one or more substances are always a metal.

Bronze: copper + tin Steel: iron + carbon

Unit 6 MATTER SUMMARY

FORCES A force is a push or pull that acts on an object. We can’t see forces, but we can see and feel their effects. Forces can make things move, stop, speed up, slow down, or change direction. Forces can also make things change shape.

CONTACT FORCES They act through physical contact.

- Friction: is the force that exists when two objects rub against each other. Friction acts in the opposite direction to the direction of movement. It can slow down or stop a moving object. Air friction slows down a parachute and water friction slows down a kayak or a boat.

- Buoyancy- is the ability of objects to float. It is an upward force which acts in the opposite direction to gravity on objects immersed in a liquid. If you put an ice cube in a glass of water, gravity pulls the ice cube down and the buoyant force pushes it up.

NON-CONTACT FORCES They act from a distance.

- Magnetism – is a force of attraction or repulsion caused by magnetic materials. Magnets attract metals and also make compasses work.

- Gravity – is a force which attracts all objects towards the ground. Larger bodies, such as planets, have a stronger gravitational force. Gravity stops everything on Earth from flying off into outer space and also causes objects to fall to the ground. Astronauts float in space because there is no gravity there.

Types

A NEW WORLD OF MATERIALS Scientists and engineers create of modify materials to make them perform better.

IMPROVING OUR HEALTH A special ceramic material is used to place hip and knee joints for artificial joints. It is also used by the dentists for fillings, to repair teeth.

ALLOYS They are mixtures of two or more elements and one of them must be a metal. Ex steel.

RECENT BREAKTHROUGH Ex. Concrete Cloth (a durable a flexible waterproof building material of cement sandwiched between fabric that can be used to make emergency shelters)

NEW MATERIALS IN EVERYDAY LIFE Ex. Non-stick ceramic coating, polar fleece fabric.