Fun with lenses

Lenses are used in many ways such as: eye glasses, microscopes, projectors, cameras, our eyes, contact lenses, telescopes and magnifying glasses.

What is a lens?

A lens is a specially shaped piece of glass. When light hits hit the light is refracted. This means that the light changes direction slightly. When you view objects through a lens they may appear bigger, smaller, closer, further away or upside down.


This is a convex lens and it makes my eye look larger.


This is a concave lens and it makes my face look smaller.


If you use 2 magnifying glasses at once the image will be even bigger.


A simple telescope can be made out of 2 lenses. We tried using to convex lenses and the image appeared upside down. When we used a concave and convex lenses the image was the right way up.

Can light travel around corners?

This was the question that the Year 5 and 6 students were posed this week.

Our main focus for the lesson was to give evidence to support the answer to the question. The students needed to understand that as scientists they could say something but for people to believe them they need proof.

The students did 2 investigation to gather evidence to support their answer to the question.

This picture shows us testing where a beam of light goes. We found out that light can only go in a straight line. The light was mostly blocked by the card but some of the light traveled through the holes and we could see it come out the other end. The light did not travel around the card because we could see a shadow behind the card.

Here we are trying to make it look like a beam of light is shining through a book. But really we are reflecting the light around the book.

Using the evidence gathered we came to these conclusions:

• Light always travels in a straight line from its source until it hits something.
• When light hits something shiny it will reflect off in a straight line.
• Light can only go around corners if it is reflected.
  

How can you separate a mixure?

Our 5 year olds know what a mixture is. To make a mixture you have to mix together 2 or more different things. They made fruit salad by mixing together many different pieces of fruit. This mixture was easy to separate back into the different parts but for some mixtures this is not so easy.

Look at the different ways we found for separating mixtures.

Sorting


Sieving


Filtering

Conductors and Insulators

Did you know that electricity can only flow through some materials? Well the clever Year 3 and 4 students do.

They made electrical circuits then put different materials into the circuit to see if the electricity would flow through and light the bulb.

They found out that only metal things would let the electricity through. These have a special name called conductors.

Things made from plastic, glass, wood, paper, fabric, stone, shell and rubber did not let electricity through. These have a special name called insulators.

Changes when a candle burns

This week the Year 5 and 6 classes found out that there are many changes that occur when a candle burns.

So what is produced when a candle burns?

• You sometimes get smoke and soot (which is particles of partly burnt wax)
  
• The wax changes into melted wax.
• Carbon Dioxide and Water are produced from the chemical reaction between the oxygen and the fuel in the flame.

These photos show how we collected soot from the burning candle. We held the tinfoil above the flame, in the top of the flame and near the bottom of the flame.

Miss Harrison challenged us to think about whether these changes were reversible or irreversible (permanent).

This is what we came up with.

Reversible Changes
The only reversible change is the melted wax. When you let the melted wax cool down it turns back into solid wax. You could reshape this wax into a new candle.

Irreversible Changes
The main irreversible change is the water and carbon dioxide. This was formed from the chemical reaction between the fuel and the oxygen and you can't change them back.

Parts of a flower

The Year 5 and 6 Science Club students were the first to use our new microscopes this week.

We brought in a collection of flowers which we first dissected into the different parts.

Then we carefully observed the different parts under the microscope. We were amazed at what we saw.

Parts of a flower - viewed by a microscope on PhotoPeach

Extinguishing a Candle

For a flame to burn it needs 3 things:

• Oxygen
• Fuel
• Heat

This is called the Fire Triangle. If you remove one of these things the flame will be extinguished.

This week the Year 5 and 6 classes investigated what would happen if they put a jar upside down over a candle. They predicted that the flame would go out because all the oxygen would get used up.

The students had to observe the flame carefully to ensure it had gone out before they lifted off the jar. Sometimes the flame was not out and when the jar was lifted oxygen got to the candle and the flame got bigger.

Then they used a range of jar sizes to see if this made a difference to the time the flame burnt for.
After 1 test they found out that the candle in the small jar extinguished before the candle in the large jar. However, they decided to do more testing just in case this was a coincidence.

After more trials they found out that every time the candles in the smaller jars were extinguished the quickest.

Why does this happen? Everyone decided that it was because the biggest jar had the most oxygen inside it so the flame could burn for longer. As the candle burnt it used up the oxygen and gave out carbon dioxide. The carbon dioxide would also help to extinguish the flame.