Topic 1 - Matter PDF

Topic 1: Matter Matter refers to everything which occupies space, and has mass which exists in one of three physical states, solid, liquid and gaseous. Matter itself is made up of small particles. The simplest forms of matter are the elements, whose constituent particles are called atoms, as mod...

Topic 1: Matter Matter refers to everything which occupies space, and has mass which exists in one of three physical states, solid, liquid and gaseous. Matter itself is made up of small particles. The simplest forms of matter are the elements, whose constituent particles are called atoms, as modelled below. Atoms are largely space with a relatively dense nucleus made up of elementary particles, protons and neutrons, and one or more shells of electrons at certain fixed distances. Each shell represents an energy level within the atom. Within the atom four fundamental interactions: 1. Gravity. This is the same as already discussed, but very insignificant on the 2. The Weak Nuclear Interaction, which contributes to radio activity. 3. The Electromagnetic Interaction. Acts between the nucleus and electrons and is 4. the source of electrical and magnetic energy. 5. The Strong Nuclear Interaction. Holds the nuclei together. Proton has positive electric charge and neutron has a negative electric charge. Pure copper is an element because it is comprised only of copper atoms (Cu). An atom is the smallest part of an element that retains the properties of that element. All atoms follow this rule: Maximum number of electrons possible in each shell = 2n2 where n is the shell number. Each atom has an identifiable number of protons, neutrons, and electrons. In addition, every atom has its own atomic number, as well as its own atomic mass Ions Atoms which have **lost or gained** an **electron** during a process. An **atom losing an** **electron will become positive, whilst an atom gaining an electron will become** **negative.** Isotopes Atoms of the **same element with different numbers of neutrons**. The Atomic Number remains the same, but the Atomic Mass changes. COMPOUNDS There are 109 known elements currently, however most of the matter around us has been formed by one or more elements combining in such a way to form completely new substances called compounds. This is called **chemical bonding**, and generally when atoms bond together, they **share** **or transfer electrons and form molecules**. A compound is matter in which all the molecules are identical, but the molecules are comprised of different atoms in exact proportions. MIXTURES A mixture is a mingled mass of two or more substances where each substance retains it own individual characteristics. For example, Fig 1.4 is a representation of NaCl in H2O (salty water). Mixtures have varying ratios of ingredients that **do not combine chemically** as they do in a compound. STATES OF MATTER All atoms and molecules in matter are **constantly in vibratory motion**. The degree of motion i.e. the internal kinetic energy possessed by the matter, determines its physical state. This internal KE is what we know as heat. What we call 'temperature' is, in fact, only a measure of this molecular activity Solids A solid has a definite volume and shape, and is independent of its container. For example, a rock that is put into a jar does not reshape itself to form to the jar. In a solid there is very little heat energy and, therefore, the molecules or atoms cannot move very far from their relative position. For this reason a solid is incompressible , that is, has constant density. Liquids When heat energy is added to solid matter, its molecular movement increases. This causes the molecules to overcome their rigid shape. When a material changes from a solid to a liquid, the material's volume does not significantly change. However, the material conforms to the shape of the container its held in. Liquids have definite volume but not shape. Liquids are also incompressible. Gas As heat energy is continually added to a material, the molecular movement increases further until the liquid reaches a point where surface tension can no longer hold the molecules down. At this point the molecules escape, becoming gas or vapour. Gases differ from solids and liquids in the fact that they have neither a definite shape nor volume. However, because the molecules in a gas are spread out, gasses are compressible. Flow The same property that allows liquids and gases to adopt the shape of their containers, also allows them to flow, and they can both be called fluids.