Science

A liquid, or fluid, is something that has no shape of its own. It flows around and takes the shape of whatever container it is put into. Water is the liquid most of us are familiar with. When something solid like butter melts, it turns into a liquid.

Melting is the process of something changing from a solid to a liquid. When ice melts it becomes water. When ice cream melts, it makes a mess.
You can find lots of things around the house that can be melted in a frypan or saucepan, like butter, cheese and chocolate.

A prism is a clear, solid object, usually shaped with a triangle on the top and bottom and straight sides. Prisms are used to change the direction of light, or to split it up into its colours like a rainbow.

A reflection is an image of something else, as seen in a shiny, reflective surface like a mirror.
In the picture, you can see a reflection of the tree in the water.

When you stand in front of a light like the sun, some of the light hits you and some of the light goes past you. Where you are in the way between the sun and the ground, there will be a shadow. A shadow is just somewhere there is less light than there is around it. Shadows are the same shape as whatever is blocking the light.
Shadows change size and shape depending on how high or low the light is. Shadows are darker and clearer when the light is strong and coming from only one direction. You can make shadow puppets with your hands or some cut-out shapes, a light and a wall.

Smoke is given off when you burn something. Smoke is made up of byproduct gases and small particles from the burning process. Most of the particles are small specs of soot.
The smoke in the picture is a smoke bomb some students made in a science class at a school.

A spark is a tiny piece of something, usually metal, that is glowing red-hot. Sparks are often made when you strike two surfaces together very hard and bits of one surface are broken off. The sparks in the picture were made by an angle grinder.

Steam is made when water boils. Steam that you see coming out of a kettle isn't actually a gas, it is a mist of water made as the invisible, gaseous water condenses in the air to form tiny droplets. This is the same process that makes clouds.