Matter Junior Science

Understand that matter is made up of particles /atoms An atom is the smallest neutral particle that makes up matter. The type of atom and the way these atoms are arranged and connected to each other determines the type of matter – and therefore the physical and chemical properties of the matter.

Matter is made up of particles /atoms (everything) Elements Substances made up of only one type of atom Mixtures combinations of elements and/or compounds that can be separated by physical means Compounds Combinations of two or more elements that are bonded together Atom The smallest neutral particle all matter is formed from Molecule Two or more atoms bonded forming the smallest unit

Molecules are made from Atoms 1b Molecules are made from Atoms A molecule forms when atoms join together – either the same type of atom to form a molecule of an element (such as oxygen gas – made from 2 oxygen atoms) or different types of atom to form a molecule of a compound (such as water - made from 2 hydrogen and one oxygen atom). Oxygen Molecule – O2 Water Molecule – H2O

Elements are pure substances that combine to make mixtures & compounds Extra for experts Matter can be divided into pure substances which include elements (atoms of the same type) and compounds (different atoms joined together) and Mixtures which can either be homogeneous (evenly mixed) or heterogeneous (unevenly mixed)

Matter exists in different states – solid, liquid and gases All matter can be found as either solid, liquid or gas depending upon the temperature. Each type of matter has its own specific temperature ranges that it will exist in each of these three states. Gases, liquids and solids can be made up of atoms, molecules, and/or ions. solid liquid gas

Matter exists in different states – solid, liquid and gases 2b Matter exists in different states – solid, liquid and gases Solids remain in a fixed shape – the particles vibrate but remain tightly bonded to each other. Liquids take the shape of the container – the particles can move past each other but are still bonded. Gases fill any container they are in – the particles move fast and are not bonded to each other

2b Particles are arranged and move differently in solids, liquids and gases Solid particles are packed closely and only vibrate in a fixed position. Liquid particles are also packed closely but the particles move around more. Gas particles have a lot of space between them and move around quickly.

Characteristics of Gases, Liquids and Solids 2b Particles are arranged and move differently in solids, liquids and gases Characteristics of Gases, Liquids and Solids gas liquid solid assumes the shape and volume of its container particles can move past one another assumes the shape of the part of the container which it occupies particles can move/slide past one another retains a fixed volume and shape rigid - particles locked into place compressible lots of free space between particles not easily compressible little free space between particles flows easily particles can move/slide past one another does not flow easily rigid - particles cannot move/slide past one another 9 9

Matter can change from one state to another condensation Gas evaporating sublimation deposition Liquid Freezing If energy is absorbed or released the particles which make up the matter can change state. A change of state is a physical reaction and it is reversible. Solid Melting

The particles of different states have different kinetic energy levels Extra for experts Kinetic energy causes particles to move. The more kinetic energy a particle has the faster it moves. Kinetic energy can be added to a particle by adding heat energy (and heats up). The heat energy is then transformed into the kinetic energy. Kinetic energy can also be lost from a particle, which slows it down, when it changes back into heat energy and is lost (and cools).

The particles of different states have different kinetic energy levels Extra for experts The movement of particles in any state is determined by three factors: How strong the bonds are between the particles, how much energy (kinetic) the particles contain and the mass of the particles. Particles move faster when: they have less mass, have weaker bonds between particles and have more energy. Particles move slower when: they have more mass, have stronger bonds between particles and have less energy.

Temperature is a measure of the kinetic energy in particles. 3b Temperature is a measure of the kinetic energy in particles. Extra for experts The atoms and molecules in a gas are in constant motion. Temperature is a measure of the speed with which they move. (More exactly it is a measure of their kinetic energy.) The higher the temperature, the faster the molecules move.

Heat/temperature is linked to particle movement 3b Extra for experts Heat/temperature is linked to particle movement Heat and temperature are not the same thing. Heat energy is the total kinetic energy of the atoms of a substance. Temperature is the average kinetic energy of the atoms of a substance. We measure our temperature on the Celsius scale where water freezes at 0°C and boils at 100°C. Other countries use the Fahrenheit scale and Scientists often use the Kelvin scale.

Melting and boiling points 3c Melting and boiling points The temperature at which a substance changes from a solid into a liquid is called it’s melting point. The temperature at which a substance changes from a liquid into a gas is called it’s boiling point. Different types of substances have different melting and boiling points – these are determined by how strong the bonds are between particles or molecules. When a molecule melts or boils it is the bonds between the molecule that break not the bonds inside a molecule holding the atoms together.

Melting and boiling points of water 3c Melting and boiling points of water The melting point of water is 0˚C. This is the temperature where the water molecules have enough kinetic energy to break away from a solid state into a liquid state. The boiling point of water is 100˚C. This is the temperature where the water molecules have enough kinetic energy to completely break away from each other and form a gas. Melting And boiling points of water The melting point and boiling point are just average temperatures when a change of state occurs. For example some water particles will change from liquid to gas at much lower temperatures than 100˚C, such as water evapourating off a road after rain.

Latent heat is the heat released or absorbed by a material during a change of state without change of temperature. 3c Extra for experts There is no temperature change during a phase change (change of state), thus there is no change in the kinetic energy of the particles in the material. The energy released ( to change from gas to liquid or liquid to solid) comes from the potential energy stored in the bonds between the particles. The energy absorbed (to change from gas to liquid or liquid to gas) comes from the surrounding area. extension

Expansion and Contraction of matter 4a/b Expansion and Contraction of matter Matter expands or gets bigger when it is heated up. It contracts or gets smaller when it is cooled down. Some types of matter, such as metals, conduct heat very well and therefore the effects of expansion and contraction are more obvious. Structures such as bridges and railway tracks that are made out of metal have to be built with gaps so they don’t warp out of shape when exposed to higher temperatures during summer.

Expansion and Contraction of matter 4a/b Expansion and Contraction of matter When matter expands or contracts only the space between the particles changes: not the size of the particles. The particles in a solid vibrate more when it is heated, and take up more space. The particles in a liquid move around each other more when it is heated, and take up more space. The particles in a gas move more quickly in all directions when it is heated, and take up more space.

Expansion, Contraction and Density in Gases 4a/b Expansion, Contraction and Density in Gases As matter expands the density (mass of matter in a given volume) will decrease making it “lighter”. In a gas the warmer particles that are moving faster due to their increased kinetic energy are colliding with each other more. This creates more space between the particles and therefore makes that area of gas less dense. The less dense gas will rise above the colder more dense. This is why hot air rises to the top of a ceiling in a heated house. Heat expands the space between air particles and cause the balloon to inflate when heated Heating water to create expanding steam powered many engines and began the industrial revolution

Expansion, Contraction and Density in liquids 4a/b Expansion, Contraction and Density in liquids In liquids the hotter and expanded, less dense substance rises above cooler and denser liquids. This creates convection currents and causes the movement of particles containing heat energy. Molten Magma under the earth’s surface moves due to convection currents when the heat from the Earth’s core causes it to expand. When the magma reaches the earth’s surface under the crust it cools, contracts and gains in density, so it sinks again.

The theory of Brownian motion Extra for experts The theory of Brownian motion Brownian motion is the random movement of particles in a liquid or gas, caused by the particles hitting (or colliding) with molecules they are surrounded by. Each collision pushes particles in a random direction and is the reason why diffusion occurs. Pollen particles that could be seen moving randomly in water was first described by Robert Brown in the early 1800's. Brown was a Scottish botanist. In 1905 Einstein finally came up with an explanation when he realised that the jiggling of the pollen grains seen in Brownian motion was due to molecules of water hitting the tiny pollen grains. He was also able to use this evidence to prove the existence of atoms which up to that point had only been an idea.

Diffusion occurs because particles mix with and move through another substance When particles diffuse they move from an area of high concentration ( many particles in a given area) spreading out into areas of low concentration (fewer particles in a given area). Diffusion will continue until the particles are evenly spread out – this is then called equilibrium. Diffusion occurs because the particles move around due to kinetic energy. When they hit into each other they are pushed apart. This causes the particles to spread out and diffuse.